Cretonne Language Reference¶
The Cretonne intermediate language (IL) has two equivalent
representations: an inmemory data structure that the code generator library
is using, and a text format which is used for test cases and debug output.
Files containing Cretonne textual IL have the .cton
filename extension.
This reference uses the text format to describe IL semantics but glosses over the finer details of the lexical and syntactic structure of the format.
Overall structure¶
Cretonne compiles functions independently. A .cton
IL file may contain
multiple functions, and the programmatic API can create multiple function
handles at the same time, but the functions don’t share any data or reference
each other directly.
This is a simple C function that computes the average of an array of floats:
float
average(const float *array, size_t count)
{
double sum = 0;
for (size_t i = 0; i < count; i++)
sum += array[i];
return sum / count;
}
Here is the same function compiled into Cretonne IL:
function average(i32, i32) > f32 {
ss1 = stack_slot 8 ; Stack slot for ``sum``.
ebb1(v1: i32, v2: i32):
v3 = f64const 0x0.0
stack_store v3, ss1
brz v2, ebb3 ; Handle count == 0.
v4 = iconst.i32 0
jump ebb2(v4)
ebb2(v5: i32):
v6 = imul_imm v5, 4
v7 = iadd v1, v6
v8 = heap_load.f32 v7 ; array[i]
v9 = fpromote.f64 v8
v10 = stack_load.f64 ss1
v11 = fadd v9, v10
stack_store v11, ss1
v12 = iadd_imm v5, 1
v13 = icmp ult v12, v2
brnz v13, ebb2(v12) ; Loop backedge.
v14 = stack_load.f64 ss1
v15 = fcvt_from_uint.f64 v2
v16 = fdiv v14, v15
v17 = fdemote.f32 v16
return v17
ebb3:
v100 = f32const +NaN
return v100
}
The first line of a function definition provides the function name and
the function signature which declares the argument and return types.
Then follows the function preamble which declares a number of entities
that can be referenced inside the function. In the example above, the preamble
declares a single local variable, ss1
.
After the preamble follows the function body which consists of extended basic blocks, the first of which is the entry block. Every EBB ends with a terminator instruction, so execution can never fall through to the next EBB without an explicit branch.
A .cton
file consists of a sequence of independent function definitions:
function_list ::= { function } function ::= function_spec "{" preamble function_body "}" function_spec ::= "function" function_name signature preamble ::= { preamble_decl } function_body ::= { extended_basic_block }
Static single assignment form¶
The instructions in the function body use and produce values in SSA form. This means that every value is defined exactly once, and every use of a value must be dominated by the definition.
Cretonne does not have phi instructions but uses EBB arguments instead. An EBB can be defined with a list of typed arguments. Whenever control is transferred to the EBB, values for the arguments must be provided. When entering a function, the incoming function arguments are passed as arguments to the entry EBB.
Instructions define zero, one, or more result values. All SSA values are either EBB arguments or instruction results.
In the example above, the loop induction variable i
is represented as three
SSA values: In the entry block, v4
is the initial value. In the loop block
ebb2
, the EBB argument v5
represents the value of the induction
variable during each iteration. Finally, v12
is computed as the induction
variable value for the next iteration.
It can be difficult to generate correct SSA form if the program being converted
into Cretonne IL contains multiple assignments to the same variables.
Such variables can be presented to Cretonne as stack slots instead.
Stack slots are accessed with the stack_store
and stack_load
instructions which behave more like variable accesses in a typical programming
language. Cretonne can perform the necessary dataflow analysis to convert stack
slots to SSA form.
Value types¶
All SSA values have a type which determines the size and shape (for SIMD vectors) of the value. Many instructions are polymorphic – they can operate on different types.
Boolean types¶
Boolean values are either true or false. While this only requires a single bit
to represent, more bits are often used when holding a boolean value in a
register or in memory. The b1
type represents an abstract boolean
value. It can only exist as an SSA value, it can’t be stored in memory or
converted to another type. The larger boolean types can be stored in memory.
Todo
Clarify the representation of larger boolean types.
The multibit boolean types can be interpreted in different ways. We could declare that zero means false and nonzero means true. This may require unwanted normalization code in some places.
We could specify a fixed encoding like all ones for true. This would then lead to undefined behavior if untrusted code uses the multibit booleans incorrectly.
Something like this:
 External code is not allowed to load/store multibit booleans or otherwise expose the representation.
 Each target specifies the exact representation of a multibit boolean.

b1
¶ A boolean value that is either true or false.
Bytes: Can’t be stored in memory

b8
¶ A boolean type with 8 bits.
Bytes: 1

b16
¶ A boolean type with 16 bits.
Bytes: 2

b32
¶ A boolean type with 32 bits.
Bytes: 4

b64
¶ A boolean type with 64 bits.
Bytes: 8
Integer types¶
Integer values have a fixed size and can be interpreted as either signed or unsigned. Some instructions will interpret an operand as a signed or unsigned number, others don’t care.

i8
¶ An integer type with 8 bits.
Bytes: 1

i16
¶ An integer type with 16 bits.
Bytes: 2

i32
¶ An integer type with 32 bits.
Bytes: 4

i64
¶ An integer type with 64 bits.
Bytes: 8
Floating point types¶
The floating point types have the IEEE semantics that are supported by most hardware. There is no support for higherprecision types like quads or doubledouble formats.

f32
¶ A 32bit floating point type represented in the IEEE 7542008 binary32 interchange format. This corresponds to the
float
type in most C implementations.Bytes: 4

f64
¶ A 64bit floating point type represented in the IEEE 7542008 binary64 interchange format. This corresponds to the
double
type in most C implementations.Bytes: 8
SIMD vector types¶
A SIMD vector type represents a vector of values from one of the scalar types (boolean, integer, and floating point). Each scalar value in a SIMD type is called a lane. The number of lanes must be a power of two in the range 2256.

i
Bx
N¶ A SIMD vector of integers. The lane type
iB
is one of the integer typesi8
...i64
.Some concrete integer vector types are
i32x4
,i64x8
, andi16x4
.The size of a SIMD integer vector in memory is \(N B\over 8\) bytes.

f32x
N¶ A SIMD vector of single precision floating point numbers.
Some concrete
f32
vector types are:f32x2
,f32x4
, andf32x8
.The size of a
f32
vector in memory is \(4N\) bytes.
Pseudotypes and type classes¶
These are not concrete types, but convenient names uses to refer to real types in this reference.

iPtr
¶ A Pointersized integer.
This is either
i32
, ori64
, depending on whether the target platform has 32bit or 64bit pointers.

T
x
N¶ Any SIMD vector type.
Immediate operand types¶
These types are not part of the normal SSA type system. They are used to indicate the different kinds of immediate operands on an instruction.

imm64
¶ A 64bit immediate integer. The value of this operand is interpreted as a signed two’s complement integer. Instruction encodings may limit the valid range.
In the textual format,
imm64
immediates appear as decimal or hexadecimal literals using the same syntax as C.

offset32
¶ A signed 32bit immediate address offset.
In the textual format,
offset32
immediates always have an explicit sign, and a 0 offset may beomitted.

ieee32
¶ A 32bit immediate floating point number in the IEEE 7542008 binary32 interchange format. All bit patterns are allowed.

ieee64
¶ A 64bit immediate floating point number in the IEEE 7542008 binary64 interchange format. All bit patterns are allowed.
The two IEEE floating point immediate types ieee32
and ieee64
are displayed as hexadecimal floating point literals in the textual IL
format. Decimal floating point literals are not allowed because some computer
systems can round differently when converting to binary. The hexadecimal
floating point format is mostly the same as the one used by C99, but extended
to represent all NaN bit patterns:
 Normal numbers
 Compatible with C99:
0x1.Tpe
whereT
are the trailing significand bits encoded as hexadecimal, ande
is the unbiased exponent as a decimal number.ieee32
has 23 trailing significand bits. They are padded with an extra LSB to produce 6 hexadecimal digits. This is not necessary forieee64
which has 52 trailing significand bits forming 13 hexadecimal digits with no padding.  Zeros
 Positive and negative zero are displayed as
0.0
and0.0
respectively.  Subnormal numbers
 Compatible with C99:
0x0.Tpemin
whereT
are the trailing significand bits encoded as hexadecimal, andemin
is the minimum exponent as a decimal number.  Infinities
 Either
Inf
orInf
.  Quiet NaNs
 Quiet NaNs have the MSB of the trailing significand set. If the remaining
bits of the trailing significand are all zero, the value is displayed as
NaN
orNaN
. Otherwise,NaN:0xT
whereT
are the trailing significand bits encoded as hexadecimal.  Signaling NaNs
 Displayed as
sNaN:0xT
.
Control flow¶
Branches transfer control to a new EBB and provide values for the target EBB’s arguments, if it has any. Conditional branches only take the branch if their condition is satisfied, otherwise execution continues at the following instruction in the EBB.

jump
EBB(args...)¶ Jump.
Unconditionally jump to an extended basic block, passing the specified EBB arguments. The number and types of arguments must match the destination EBB.
Arguments:  EBB (ebb) – Destination extended basic block
 args (variable_args) – EBB arguments

fallthrough
EBB(args...)¶ Fall through to the next EBB.
This is the same as
jump
, except the destination EBB must be the next one in the layout.Jumps are turned into fallthrough instructions by the branch relaxation pass. There is no reason to use this instruction outside that pass.
Arguments:  EBB (ebb) – Destination extended basic block
 args (variable_args) – EBB arguments

brz
c, EBB(args...)¶ Branch when zero.
If
c
is ab1
value, take the branch whenc
is false. Ifc
is an integer value, take the branch whenc = 0
.Arguments:  c (Testable) – Controlling value to test
 EBB (ebb) – Destination extended basic block
 args (variable_args) – EBB arguments
Type Variables:  Testable – inferred from c

brnz
c, EBB(args...)¶ Branch when nonzero.
If
c
is ab1
value, take the branch whenc
is true. Ifc
is an integer value, take the branch whenc != 0
.Arguments:  c (Testable) – Controlling value to test
 EBB (ebb) – Destination extended basic block
 args (variable_args) – EBB arguments
Type Variables:  Testable – inferred from c

br_icmp
Cond, x, y, EBB(args...)¶ Compare scalar integers and branch.
Compare
x
andy
in the same way as theicmp
instruction and take the branch if the condition is true:br_icmp ugt v1, v2, ebb4(v5, v6)
is semantically equivalent to:
v10 = icmp ugt, v1, v2 brnz v10, ebb4(v5, v6)
Some RISC architectures like MIPS and RISCV provide instructions that implement all or some of the condition codes. The instruction can also be used to represent macroop fusion on architectures like Intel’s.
Arguments: Type Variables:  iB – inferred from x

br_table
x, JT¶ Indirect branch via jump table.
Use
x
as an unsigned index into the jump tableJT
. If a jump table entry is found, branch to the corresponding EBB. If no entry was found fall through to the next instruction.Note that this branch instruction can’t pass arguments to the targeted blocks. Split critical edges as needed to work around this.
Arguments:  x (iB) – index into jump table
 JT (jump_table) – A jump table.
Type Variables:  iB – inferred from x

JT =
jump_table
EBB0, EBB1, ..., EBBn¶ Declare a jump table in the function preamble.
This declares a jump table for use by the
br_table
indirect branch instruction. Entries in the table are either EBB names, or0
which indicates an absent entry.The EBBs listed must belong to the current function, and they can’t have any arguments.
Arguments:  EBB0 – Target EBB when
x = 0
.  EBB1 – Target EBB when
x = 1
.  EBBn – Target EBB when
x = n
.
Result: A jump table identifier. (Not an SSA value).
 EBB0 – Target EBB when
Traps stop the program because something went wrong. The exact behavior depends
on the target instruction set architecture and operating system. There are
explicit trap instructions defined below, but some instructions may also cause
traps for certain input value. For example, udiv
traps when the divisor
is zero.

trap
¶ Terminate execution unconditionally.
Function calls¶
A function call needs a target function and a function signature. The target function may be determined dynamically at runtime, but the signature must be known when the function call is compiled. The function signature describes how to call the function, including arguments, return values, and the calling convention:
signature ::= "(" [arglist] ")" [">" retlist] [call_conv]
arglist ::= arg { "," arg }
retlist ::= arglist
arg ::= type [argext] [argspecial]
argext ::= "uext"  "sext"
argspecial ::= "sret"  "link"  "fp"  "csr"
callconv ::= string
Arguments and return values have flags whose meaning is mostly target dependent. They make it possible to call native functions on the target platform. When calling other Cretonne functions, the flags are not necessary.
Functions that are called directly must be declared in the function preamble:

FN =
function
NAME signature¶ Declare a function so it can be called directly.
Arguments:  NAME – Name of the function, passed to the linker for resolution.
 signature – Function signature. See below.
Results:  FN – A function identifier that can be used with
call
.

rvals =
call
FN(args...)¶ Direct function call.
Call a function which has been declared in the preamble. The argument types must match the function’s signature.
Arguments:  FN (func_ref) – function to call, declared by
function
 args (variable_args) – call arguments
Results:  rvals (variable_args) – return values
 FN (func_ref) – function to call, declared by

return
rvals...¶ Return from the function.
Unconditionally transfer control to the calling function, passing the provided return values. The list of return values must match the function signature’s return types.
Arguments:  rvals (variable_args) – return values
This simple example illustrates direct function calls and signatures:
function gcd(i32 uext, i32 uext) > i32 uext "C" {
fn1 = function divmod(i32 uext, i32 uext) > i32 uext, i32 uext
ebb1(v1: i32, v2: i32):
brz v2, ebb2
v3, v4 = call fn1(v1, v2)
br ebb1(v2, v4)
ebb2:
return v1
}
Indirect function calls use a signature declared in the preamble.

SIG =
signature
signature¶ Declare a function signature for use with indirect calls.
Arguments:  signature – Function signature. See
signature
.
Results:  SIG – A signature identifier.
 signature – Function signature. See

rvals =
call_indirect
SIG, callee(args...)¶ Indirect function call.
Call the function pointed to by callee with the given arguments. The called function must match the specified signature.
Arguments:  SIG (sig_ref) – function signature
 callee (iAddr) – address of function to call
 args (variable_args) – call arguments
Results:  rvals (variable_args) – return values
Type Variables:  iAddr – inferred from callee
Todo
Define safe indirect function calls.
The call_indirect
instruction is dangerous to use in a sandboxed
environment since it is not easy to verify the callee address.
We need a tabledriven indirect call instruction, similar to
br_table
.
Memory¶
Cretonne provides fully general load
and store
instructions for
accessing memory. However, it can be very complicated to verify the safety of
general loads and stores when compiling code for a sandboxed environment, so
Cretonne also provides more restricted memory operations that are always safe.

a =
load
Flags, p, Offset¶ Load from memory at
p + Offset
.This is a polymorphic instruction that can load any value type which has a memory representation.
Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (Mem) – Value loaded
Type Variables:  Mem – explicitly provided
 iAddr – from input operand

store
Flags, x, p, Offset¶ Store
x
to memory atp + Offset
.This is a polymorphic instruction that can store any value type with a memory representation.
Arguments: Type Variables:  Mem – inferred from x
 iAddr – from input operand
Loads and stores are misaligned if the resultant address is not a multiple of the expected alignment. Depending on the target architecture, misaligned memory accesses may trap, or they may work. Sometimes, operating systems catch alignment traps and emulate the misaligned memory access.
Extending loads and truncating stores¶
Most ISAs provide instructions that load an integer value smaller than a register and extends it to the width of the register. Similarly, store instructions that only write the low bits of an integer register are common.
Cretonne provides extending loads and truncation stores for 8, 16, and 32bit memory accesses.

a =
uload8
Flags, p, Offset¶ Load 8 bits from memory at
p + Offset
and zeroextend.This is equivalent to
load.i8
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt8) – An integer type with more than 8 bits
Type Variables:  iExt8 – explicitly provided
 iAddr – from input operand

a =
sload8
Flags, p, Offset¶ Load 8 bits from memory at
p + Offset
and signextend.This is equivalent to
load.i8
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt8) – An integer type with more than 8 bits
Type Variables:  iExt8 – explicitly provided
 iAddr – from input operand

istore8
Flags, x, p, Offset¶ Store the low 8 bits of
x
to memory atp + Offset
.This is equivalent to
ireduce.i8
followed bystore.i8
.Arguments:  Flags (memflags) – Memory operation flags
 x (iExt8) – An integer type with more than 8 bits
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Type Variables:  iExt8 – inferred from x
 iAddr – from input operand

a =
uload16
Flags, p, Offset¶ Load 16 bits from memory at
p + Offset
and zeroextend.This is equivalent to
load.i16
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt16) – An integer type with more than 16 bits
Type Variables:  iExt16 – explicitly provided
 iAddr – from input operand

a =
sload16
Flags, p, Offset¶ Load 16 bits from memory at
p + Offset
and signextend.This is equivalent to
load.i16
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt16) – An integer type with more than 16 bits
Type Variables:  iExt16 – explicitly provided
 iAddr – from input operand

istore16
Flags, x, p, Offset¶ Store the low 16 bits of
x
to memory atp + Offset
.This is equivalent to
ireduce.i16
followed bystore.i8
.Arguments:  Flags (memflags) – Memory operation flags
 x (iExt16) – An integer type with more than 16 bits
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Type Variables:  iExt16 – inferred from x
 iAddr – from input operand

a =
uload32
Flags, p, Offset¶ Load 32 bits from memory at
p + Offset
and zeroextend.This is equivalent to
load.i32
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt32) – An integer type with more than 32 bits
Type Variables:  iExt32 – explicitly provided
 iAddr – from input operand

a =
sload32
Flags, p, Offset¶ Load 32 bits from memory at
p + Offset
and signextend.This is equivalent to
load.i32
followed byuextend
.Arguments:  Flags (memflags) – Memory operation flags
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (iExt32) – An integer type with more than 32 bits
Type Variables:  iExt32 – explicitly provided
 iAddr – from input operand

istore32
Flags, x, p, Offset¶ Store the low 32 bits of
x
to memory atp + Offset
.This is equivalent to
ireduce.i32
followed bystore.i8
.Arguments:  Flags (memflags) – Memory operation flags
 x (iExt32) – An integer type with more than 32 bits
 p (iAddr) – An integer address type
 Offset (offset32) – Inbounds offset into stack slot
Type Variables:  iExt32 – inferred from x
 iAddr – from input operand
Local variables¶
One set of restricted memory operations access the current function’s stack frame. The stack frame is divided into fixedsize stack slots that are allocated in the function preamble. Stack slots are not typed, they simply represent a contiguous sequence of bytes in the stack frame.

SS =
stack_slot
Bytes, Flags...¶ Allocate a stack slot in the preamble.
If no alignment is specified, Cretonne will pick an appropriate alignment for the stack slot based on its size and access patterns.
Arguments:  Bytes – Stack slot size on bytes.
Flags:  align(N) – Request at least N bytes alignment.
Results:  SS – Stack slot index.

a =
stack_load
SS, Offset¶ Load a value from a stack slot at the constant offset.
This is a polymorphic instruction that can load any value type which has a memory representation.
The offset is an immediate constant, not an SSA value. The memory access cannot go out of bounds, i.e. \(sizeof(a) + Offset <= sizeof(SS)\).
Arguments:  SS (stack_slot) – A stack slot.
 Offset (offset32) – Inbounds offset into stack slot
Results:  a (Mem) – Value loaded
Type Variables:  Mem – explicitly provided

stack_store
x, SS, Offset¶ Store a value to a stack slot at a constant offset.
This is a polymorphic instruction that can store any value type with a memory representation.
The offset is an immediate constant, not an SSA value. The memory access cannot go out of bounds, i.e. \(sizeof(a) + Offset <= sizeof(SS)\).
Arguments:  x (Mem) – Value to be stored
 SS (stack_slot) – A stack slot.
 Offset (offset32) – Inbounds offset into stack slot
Type Variables:  Mem – inferred from x
The dedicated stack access instructions are easy for the compiler to reason about because stack slots and offsets are fixed at compile time. For example, the alignment of these stack memory accesses can be inferred from the offsets and stack slot alignments.
It can be necessary to escape from the safety of the restricted instructions by taking the address of a stack slot.

addr =
stack_addr
SS, Offset¶ Get the address of a stack slot.
Compute the absolute address of a byte in a stack slot. The offset must refer to a byte inside the stack slot: \(0 <= Offset < sizeof(SS)\).
Arguments:  SS (stack_slot) – A stack slot.
 Offset (offset32) – Inbounds offset into stack slot
Results:  addr (iAddr) – An integer address type
Type Variables:  iAddr – explicitly provided
The stack_addr
instruction can be used to macroexpand the stack access
instructions before instruction selection:
v1 = stack_load.f64 ss3, 16
; Expands to:
v9 = stack_addr ss3, 16
v1 = load.f64 v9
Heaps¶
Code compiled from WebAssembly or asm.js runs in a sandbox where it can’t access all process memory. Instead, it is given a small set of memory areas to work in, and all accesses are bounds checked. Cretonne models this through the concept of heaps.
A heap is declared in the function preamble and can be accessed with restricted
instructions that trap on outofbounds accesses. Heap addresses can be smaller
than the native pointer size, for example unsigned i32
offsets on a
64bit architecture.

H =
heap
Name¶ Declare a heap in the function preamble.
This doesn’t allocate memory, it just retrieves a handle to a sandbox from the runtime environment.
Arguments:  Name – String identifying the heap in the runtime environment.
Results:  H – Heap identifier.

a =
heap_load
p, Offset¶ Load a value at the address \(p + Offset\) in the heap H.
Trap if the heap access would be out of bounds.
Arguments:  p (iAddr) – An integer address type
 Offset (uoffset32) – Unsigned offset to effective address
Results:  a (Mem) – Value loaded
Type Variables:  Mem – explicitly provided
 iAddr – from input operand

heap_store
x, p, Offset¶ Store a value at the address \(p + Offset\) in the heap H.
Trap if the heap access would be out of bounds.
Arguments:  x (Mem) – Value to be stored
 p (iAddr) – An integer address type
 Offset (uoffset32) – Unsigned offset to effective address
Type Variables:  Mem – inferred from x
 iAddr – from input operand
When optimizing heap accesses, Cretonne may separate the heap bounds checking and address computations from the memory accesses.

addr =
heap_addr
p, Offset¶ Bounds check and compute absolute address of heap memory.
Verify that the address range
p .. p + Size  1
is valid in the heap H, and trap if not.Convert the heaprelative address in
p
to a real absolute address and return it.Arguments:  p (iAddr) – An integer address type
 Offset (uoffset32) – Unsigned offset to effective address
Results:  addr (iAddr) – An integer address type
Type Variables:  iAddr – inferred from p
A small example using heaps:
function vdup(i32, i32) {
h1 = heap "main"
ebb1(v1: i32, v2: i32):
v3 = heap_load.i32x4 h1, v1, 0
v4 = heap_addr h1, v2, 32 ; Shared range check for two stores.
store v3, v4, 0
store v3, v4, 16
return
}
The final expansion of the heap_addr
range check and address conversion
depends on the runtime environment.
Operations¶
The remaining instruction set is mostly arithmetic.
A few instructions have variants that take immediate operands (e.g.,
band
/ band_imm
), but in general an instruction is required to
load a constant into an SSA value.

a =
select
c, x, y¶ Conditional select.
This instruction selects whole values. Use
vselect
for lanewise selection.Arguments:  c (Testable) – Controlling value to test
 x (Any) – Value to use when c is true
 y (Any) – Value to use when c is false
Results:  a (Any) – Any integer, float, or boolean scalar or vector type
Type Variables:  Any – inferred from x
 Testable – from input operand
Constant materialization¶

a =
iconst
N¶ Integer constant.
Create a scalar integer SSA value with an immediate constant value, or an integer vector where all the lanes have the same value.
Arguments:  N (imm64) – A 64bit immediate integer.
Results:  a (Int) – A constant integer scalar or vector value
Type Variables:  Int – explicitly provided
Live range splitting¶
Cretonne’s register allocator assigns each SSA value to a register or a spill slot on the stack for its entire live range. Since the live range of an SSA value can be quite large, it is sometimes beneficial to split the live range into smaller parts.
A live range is split by creating new SSA values that are copies or the
original value or each other. The copies are created by inserting copy
,
spill
, or fill
instructions, depending on whether the values
are assigned to registers or stack slots.
This approach permits SSA form to be preserved throughout the register allocation pass and beyond.

a =
copy
x¶ Registerregister copy.
This instruction copies its input, preserving the value type.
A pure SSAform program does not need to copy values, but this instruction is useful for representing intermediate stages during instruction transformations, and the register allocator needs a way of representing register copies.
Arguments:  x (Any) – Any integer, float, or boolean scalar or vector type
Results:  a (Any) – Any integer, float, or boolean scalar or vector type
Type Variables:  Any – inferred from x

a =
spill
x¶ Spill a register value to a stack slot.
This instruction behaves exactly like
copy
, but the result value is assigned to a spill slot.Arguments:  x (Any) – Any integer, float, or boolean scalar or vector type
Results:  a (Any) – Any integer, float, or boolean scalar or vector type
Type Variables:  Any – inferred from x

a =
fill
x¶ Load a register value from a stack slot.
This instruction behaves exactly like
copy
, but creates a new SSA value for the spilled input value.Arguments:  x (Any) – Any integer, float, or boolean scalar or vector type
Results:  a (Any) – Any integer, float, or boolean scalar or vector type
Type Variables:  Any – inferred from x
Vector operations¶

lo, hi =
vsplit
x¶ Split a vector into two halves.
Split the vector x into two separate values, each containing half of the lanes from
x
. The result may be two scalars ifx
only had two lanes.Arguments:  x (TxN) – Vector to split
Results:  lo (half_vector(TxN)) – Lownumbered lanes of x
 hi (half_vector(TxN)) – Highnumbered lanes of x
Type Variables:  TxN – inferred from x

a =
vconcat
x, y¶ Vector concatenation.
Return a vector formed by concatenating
x
andy
. The resulting vector type has twice as many lanes as each of the inputs. The lanes ofx
appear as the lownumbered lanes, and the lanes ofy
become the highnumbered lanes ofa
.It is possible to form a vector by concatenating two scalars.
Arguments:  x (Any128) – Lownumbered lanes
 y (Any128) – Highnumbered lanes
Results:  a (double_vector(Any128)) – Concatenation of x and y
Type Variables:  Any128 – inferred from x

a =
vselect
c, x, y¶ Vector lane select.
Select lanes from
x
ory
controlled by the lanes of the boolean vectorc
.Arguments:  c (as_bool(TxN)) – Controlling vector
 x (TxN) – Value to use where c is true
 y (TxN) – Value to use where c is false
Results:  a (TxN) – A SIMD vector type
Type Variables:  TxN – inferred from x

a =
splat
x¶ Vector splat.
Return a vector whose lanes are all
x
.Arguments:  x (lane_of(TxN)) – None
Results:  a (TxN) – A SIMD vector type
Type Variables:  TxN – explicitly provided

a =
insertlane
x, Idx, y¶ Insert
y
as laneIdx
in x.The lane index,
Idx
, is an immediate value, not an SSA value. It must indicate a valid lane index for the type ofx
.Arguments:  x (TxN) – SIMD vector to modify
 Idx (uimm8) – Lane index
 y (lane_of(TxN)) – New lane value
Results:  a (TxN) – A SIMD vector type
Type Variables:  TxN – inferred from x

a =
extractlane
x, Idx¶ Extract lane
Idx
fromx
.The lane index,
Idx
, is an immediate value, not an SSA value. It must indicate a valid lane index for the type ofx
.Arguments:  x (TxN) – A SIMD vector type
 Idx (uimm8) – Lane index
Results:  a (lane_of(TxN)) – None
Type Variables:  TxN – inferred from x
Integer operations¶

a =
icmp
Cond, x, y¶ Integer comparison.
The condition code determines if the operands are interpreted as signed or unsigned integers.
Signed Unsigned Condition eq eq Equal ne ne Not equal slt ult Less than sge uge Greater than or equal sgt ugt Greater than sle ule Less than or equal When this instruction compares integer vectors, it returns a boolean vector of lanewise comparisons.
Arguments: Results:  a (as_bool(Int)) – None
Type Variables:  Int – inferred from x

a =
icmp_imm
Cond, x, Y¶ Compare scalar integer to a constant.
This is the same as the
icmp
instruction, except one operand is an immediate constant.This instruction can only compare scalars. Use
icmp
for lanewise vector comparisons.Arguments: Results:  a (b1) – A boolean value that is either true or false.
Type Variables:  iB – inferred from x

a =
iadd
x, y¶ Wrapping integer addition: \(a := x + y \pmod{2^B}\).
This instruction does not depend on the signed/unsigned interpretation of the operands.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
iadd_imm
x, Y¶ Add immediate integer.
Same as
iadd
, but one operand is an immediate constant.Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
iadd_cin
x, y, c_in¶ Add integers with carry in.
Same as
iadd
with an additional carry input. Computes:\[a = x + y + c_{in} \pmod 2^B\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from y

a, c_out =
iadd_cout
x, y¶ Add integers with carry out.
Same as
iadd
with an additional carry output.\[\begin{split}a &= x + y \pmod 2^B \\ c_{out} &= x+y >= 2^B\end{split}\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results: Type Variables:  iB – inferred from x

a, c_out =
iadd_carry
x, y, c_in¶ Add integers with carry in and out.
Same as
iadd
with an additional carry input and output.\[\begin{split}a &= x + y + c_{in} \pmod 2^B \\ c_{out} &= x + y + c_{in} >= 2^B\end{split}\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results: Type Variables:  iB – inferred from y

a =
isub
x, y¶ Wrapping integer subtraction: \(a := x  y \pmod{2^B}\).
This instruction does not depend on the signed/unsigned interpretation of the operands.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
irsub_imm
x, Y¶ Immediate reverse wrapping subtraction: \(a := Y  x \pmod{2^B}\).
Also works as integer negation when \(Y = 0\). Use
iadd_imm
with a negative immediate operand for the reverse immediate subtraction.Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
isub_bin
x, y, b_in¶ Subtract integers with borrow in.
Same as
isub
with an additional borrow flag input. Computes:\[a = x  (y + b_{in}) \pmod 2^B\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from y

a, b_out =
isub_bout
x, y¶ Subtract integers with borrow out.
Same as
isub
with an additional borrow flag output.\[\begin{split}a &= x  y \pmod 2^B \\ b_{out} &= x < y\end{split}\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results: Type Variables:  iB – inferred from x

a, b_out =
isub_borrow
x, y, b_in¶ Subtract integers with borrow in and out.
Same as
isub
with an additional borrow flag input and output.\[\begin{split}a &= x  (y + b_{in}) \pmod 2^B \\ b_{out} &= x < y + b_{in}\end{split}\]Polymorphic over all scalar integer types, but does not support vector types.
Arguments: Results: Type Variables:  iB – inferred from y

a =
imul
x, y¶ Wrapping integer multiplication: \(a := x y \pmod{2^B}\).
This instruction does not depend on the signed/unsigned interpretation of the operands.
Polymorphic over all integer types (vector and scalar).
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
imul_imm
x, Y¶ Integer multiplication by immediate constant.
Polymorphic over all scalar integer types.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x
Todo
Larger multiplication results.
For example, smulx
which multiplies i32
operands to produce a
i64
result. Alternatively, smulhi
and smullo
pairs.

a =
udiv
x, y¶ Unsigned integer division: \(a := \lfloor {x \over y} \rfloor\).
This operation traps if the divisor is zero.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
udiv_imm
x, Y¶ Unsigned integer division by an immediate constant.
This instruction never traps because a divisor of zero is not allowed.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
sdiv
x, y¶ Signed integer division rounded toward zero: \(a := sign(xy) \lfloor {x \over y}\rfloor\).
This operation traps if the divisor is zero, or if the result is not representable in \(B\) bits two’s complement. This only happens when \(x = 2^{B1}, y = 1\).
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
sdiv_imm
x, Y¶ Signed integer division by an immediate constant.
This instruction never traps because a divisor of 1 or 0 is not allowed.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
urem
x, y¶ Unsigned integer remainder.
This operation traps if the divisor is zero.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
urem_imm
x, Y¶ Unsigned integer remainder with immediate divisor.
This instruction never traps because a divisor of zero is not allowed.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
srem
x, y¶ Signed integer remainder.
This operation traps if the divisor is zero.
Todo
Integer remainder vs modulus.
Clarify whether the result has the sign of the divisor or the dividend. Should we add a
smod
instruction for the case where the result has the same sign as the divisor?Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
srem_imm
x, Y¶ Signed integer remainder with immediate divisor.
This instruction never traps because a divisor of 0 or 1 is not allowed.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x
Todo
Minimum / maximum.
NEON has smin
, smax
, umin
, and umax
instructions. We should
replicate those for both scalar and vector integer types. Even if the
target ISA doesn’t have scalar operations, these are good pattern matching
targets.
Todo
Saturating arithmetic.
Mostly for SIMD use, but again these are good patterns for contraction.
Something like usatadd
, usatsub
, ssatadd
, and ssatsub
is a
good start.
Bitwise operations¶
The bitwise operations and operate on any value type: Integers, floating point numbers, and booleans. When operating on integer or floating point types, the bitwise operations are working on the binary representation of the values. When operating on boolean values, the bitwise operations work as logical operators.

a =
band
x, y¶ Bitwise and.
Arguments:  x (bits) – Any integer, float, or boolean scalar or vector type
 y (bits) – Any integer, float, or boolean scalar or vector type
Results:  a (bits) – Any integer, float, or boolean scalar or vector type
Type Variables:  bits – inferred from x

a =
band_imm
x, Y¶ Bitwise and with immediate.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
bor
x, y¶ Bitwise or.
Arguments:  x (bits) – Any integer, float, or boolean scalar or vector type
 y (bits) – Any integer, float, or boolean scalar or vector type
Results:  a (bits) – Any integer, float, or boolean scalar or vector type
Type Variables:  bits – inferred from x

a =
bor_imm
x, Y¶ Bitwise or with immediate.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
bxor
x, y¶ Bitwise xor.
Arguments:  x (bits) – Any integer, float, or boolean scalar or vector type
 y (bits) – Any integer, float, or boolean scalar or vector type
Results:  a (bits) – Any integer, float, or boolean scalar or vector type
Type Variables:  bits – inferred from x

a =
bxor_imm
x, Y¶ Bitwise xor with immediate.
Arguments: Results:  a (iB) – A scalar integer type
Type Variables:  iB – inferred from x

a =
bnot
x¶ Bitwise not.
Arguments:  x (bits) – Any integer, float, or boolean scalar or vector type
Results:  a (bits) – Any integer, float, or boolean scalar or vector type
Type Variables:  bits – inferred from x
Todo
Redundant bitwise operators.
ARM has instructions like bic(x,y) = x & ~y
, orn(x,y) = x  ~y
, and
eon(x,y) = x ^ ~y
.
The shift and rotate operations only work on integer types (scalar and vector). The shift amount does not have to be the same type as the value being shifted. Only the low B bits of the shift amount is significant.
When operating on an integer vector type, the shift amount is still a scalar type, and all the lanes are shifted the same amount. The shift amount is masked to the number of bits in a lane, not the full size of the vector type.

a =
rotl
x, y¶ Rotate left.
Rotate the bits in
x
byy
places.Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
 iB – from input operand

a =
rotl_imm
x, Y¶ Rotate left by immediate.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
rotr
x, y¶ Rotate right.
Rotate the bits in
x
byy
places.Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
 iB – from input operand

a =
rotr_imm
x, Y¶ Rotate right by immediate.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
ishl
x, y¶ Integer shift left. Shift the bits in
x
towards the MSB byy
places. Shift in zero bits to the LSB.The shift amount is masked to the size of
x
.When shifting a Bbits integer type, this instruction computes:
\[\begin{split}s &:= y \pmod B, \\ a &:= x \cdot 2^s \pmod{2^B}.\end{split}\]Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
 iB – from input operand

a =
ishl_imm
x, Y¶ Integer shift left by immediate.
The shift amount is masked to the size of
x
.Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
ushr
x, y¶ Unsigned shift right. Shift bits in
x
towards the LSB byy
places, shifting in zero bits to the MSB. Also called a logical shift.The shift amount is masked to the size of the register.
When shifting a Bbits integer type, this instruction computes:
\[\begin{split}s &:= y \pmod B, \\ a &:= \lfloor x \cdot 2^{s} \rfloor.\end{split}\]Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
 iB – from input operand

a =
ushr_imm
x, Y¶ Unsigned shift right by immediate.
The shift amount is masked to the size of the register.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x

a =
sshr
x, y¶ Signed shift right. Shift bits in
x
towards the LSB byy
places, shifting in sign bits to the MSB. Also called an arithmetic shift.The shift amount is masked to the size of the register.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
 iB – from input operand

a =
sshr_imm
x, Y¶ Signed shift right by immediate.
The shift amount is masked to the size of the register.
Arguments: Results:  a (Int) – A scalar or vector integer type
Type Variables:  Int – inferred from x
The bitcounting instructions below are scalar only.

a =
clz
x¶ Count leading zero bits.
Starting from the MSB in
x
, count the number of zero bits before reaching the first one bit. Whenx
is zero, returns the size of x in bits.Arguments:  x (iB) – A scalar integer type
Results:  a (i8) – An integer type with 8 bits.
Type Variables:  iB – inferred from x

a =
cls
x¶ Count leading sign bits.
Starting from the MSB after the sign bit in
x
, count the number of consecutive bits identical to the sign bit. Whenx
is 0 or 1, returns one less than the size of x in bits.Arguments:  x (iB) – A scalar integer type
Results:  a (i8) – An integer type with 8 bits.
Type Variables:  iB – inferred from x
Floating point operations¶
These operations generally follow IEEE 7542008 semantics.

a =
fcmp
Cond, x, y¶ Floating point comparison.
Two IEEE 7542008 floating point numbers, x and y, relate to each other in exactly one of four ways:
UN Unordered when one or both numbers is NaN. EQ When \(x = y\). (And \(0.0 = 0.0\)). LT When \(x < y\). GT When \(x > y\). The 14
floatcc
condition codes each correspond to a subset of the four relations, except for the empty set which would always be false, and the full set which would always be true.The condition codes are divided into 7 ‘ordered’ conditions which don’t include UN, and 7 unordered conditions which all include UN.
Ordered Unordered Condition ord EQ  LT  GT uno UN NaNs absent / present. eq EQ ueq UN  EQ Equal one LT  GT ne UN  LT  GT Not equal lt LT ult UN  LT Less than le LT  EQ ule UN  LT  EQ Less than or equal gt GT ugt UN  GT Greater than ge GT  EQ uge UN  GT  EQ Greater than or equal The standard C comparison operators, <, <=, >, >=, are all ordered, so they are false if either operand is NaN. The C equality operator, ==, is ordered, and since inequality is defined as the logical inverse it is unordered. They map to the
floatcc
condition codes as follows:C Cond Subset == eq EQ != ne UN  LT  GT < lt LT <= le LT  EQ > gt GT >= ge GT  EQ This subset of condition codes also corresponds to the WebAssembly floating point comparisons of the same name.
When this instruction compares floating point vectors, it returns a boolean vector with the results of lanewise comparisons.
Arguments: Results:  a (as_bool(Float)) – None
Type Variables:  Float – inferred from x

a =
fadd
x, y¶ Floating point addition.
Arguments: Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from x

a =
fsub
x, y¶ Floating point subtraction.
Arguments: Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from x

a =
fmul
x, y¶ Floating point multiplication.
Arguments: Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from x

a =
fdiv
x, y¶ Floating point division.
Unlike the integer division instructions
sdiv
andudiv
, this can’t trap. Division by zero is infinity or NaN, depending on the dividend.Arguments: Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from x

a =
sqrt
x¶ Floating point square root.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from x

a =
fma
x, y, z¶ Floating point fused multiplyandadd.
Computes \(a := xy+z\) without any intermediate rounding of the product.
Arguments: Results:  a (Float) – Result of applying operator to each lane
Type Variables:  Float – inferred from y
Sign bit manipulations¶
The sign manipulating instructions work as bitwise operations, so they don’t have special behavior for signaling NaN operands. The exponent and trailing significand bits are always preserved.

a =
fneg
x¶ Floating point negation.
Note that this is a pure bitwise operation.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (Float) –
x
with its sign bit inverted
Type Variables:  Float – inferred from x

a =
fabs
x¶ Floating point absolute value.
Note that this is a pure bitwise operation.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (Float) –
x
with its sign bit cleared
Type Variables:  Float – inferred from x
Minimum and maximum¶
These instructions return the larger or smaller of their operands. They differ in their handling of quiet NaN inputs. Note that signaling NaN operands always cause a NaN result.
When comparing zeroes, these instructions behave as if \(0.0 < 0.0\).

a =
fmin
x, y¶ Floating point minimum, propagating NaNs.
If either operand is NaN, this returns a NaN.
Arguments: Results:  a (Float) – The smaller of
x
andy
Type Variables:  Float – inferred from x
 a (Float) – The smaller of

a =
fminnum
x, y¶ Floating point minimum, suppressing quiet NaNs.
If either operand is a quiet NaN, the other operand is returned. If either operand is a signaling NaN, NaN is returned.
Arguments: Results:  a (Float) – The smaller of
x
andy
Type Variables:  Float – inferred from x
 a (Float) – The smaller of

a =
fmax
x, y¶ Floating point maximum, propagating NaNs.
If either operand is NaN, this returns a NaN.
Arguments: Results:  a (Float) – The larger of
x
andy
Type Variables:  Float – inferred from x
 a (Float) – The larger of
Rounding¶
These instructions round their argument to a nearby integral value, still represented as a floating point number.

a =
ceil
x¶ Round floating point round to integral, towards positive infinity.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (Float) –
x
rounded to integral value
Type Variables:  Float – inferred from x

a =
floor
x¶ Round floating point round to integral, towards negative infinity.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (Float) –
x
rounded to integral value
Type Variables:  Float – inferred from x
Conversion operations¶

a =
bitcast
x¶ Reinterpret the bits in x as a different type.
The input and output types must be storable to memory and of the same size. A bitcast is equivalent to storing one type and loading the other type from the same address.
Arguments:  x (Mem) – Any type that can be stored in memory
Results:  a (MemTo) – Bits of x reinterpreted
Type Variables:  MemTo – explicitly provided
 Mem – from input operand

a =
breduce
x¶ Convert x to a smaller boolean type in the platformdefined way.
The result type must have the same number of vector lanes as the input, and each lane must not have more bits that the input lanes. If the input and output types are the same, this is a noop.
Arguments:  x (Bool) – A scalar or vector boolean type
Results:  a (BoolTo) – A smaller boolean type with the same number of lanes
Type Variables:  BoolTo – explicitly provided
 Bool – from input operand

a =
bextend
x¶ Convert x to a larger boolean type in the platformdefined way.
The result type must have the same number of vector lanes as the input, and each lane must not have fewer bits that the input lanes. If the input and output types are the same, this is a noop.
Arguments:  x (Bool) – A scalar or vector boolean type
Results:  a (BoolTo) – A larger boolean type with the same number of lanes
Type Variables:  BoolTo – explicitly provided
 Bool – from input operand

a =
bint
x¶ Convert x to an integer.
True maps to 1 and false maps to 0. The result type must have the same number of vector lanes as the input.
Arguments:  x (Bool) – A scalar or vector boolean type
Results:  a (IntTo) – An integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Bool – from input operand

a =
bmask
x¶ Convert x to an integer mask.
True maps to all 1s and false maps to all 0s. The result type must have the same number of vector lanes as the input.
Arguments:  x (Bool) – A scalar or vector boolean type
Results:  a (IntTo) – An integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Bool – from input operand

a =
ireduce
x¶ Convert x to a smaller integer type by dropping high bits.
Each lane in x is converted to a smaller integer type by discarding the most significant bits. This is the same as reducing modulo \(2^n\).
The result type must have the same number of vector lanes as the input, and each lane must not have more bits that the input lanes. If the input and output types are the same, this is a noop.
Arguments:  x (Int) – A scalar or vector integer type
Results:  a (IntTo) – A smaller integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Int – from input operand

a =
uextend
x¶ Convert x to a larger integer type by zeroextending.
Each lane in x is converted to a larger integer type by adding zeroes. The result has the same numerical value as x when both are interpreted as unsigned integers.
The result type must have the same number of vector lanes as the input, and each lane must not have fewer bits that the input lanes. If the input and output types are the same, this is a noop.
Arguments:  x (Int) – A scalar or vector integer type
Results:  a (IntTo) – A larger integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Int – from input operand

a =
sextend
x¶ Convert x to a larger integer type by signextending.
Each lane in x is converted to a larger integer type by replicating the sign bit. The result has the same numerical value as x when both are interpreted as signed integers.
The result type must have the same number of vector lanes as the input, and each lane must not have fewer bits that the input lanes. If the input and output types are the same, this is a noop.
Arguments:  x (Int) – A scalar or vector integer type
Results:  a (IntTo) – A larger integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Int – from input operand

a =
fpromote
x¶ Convert x to a larger floating point format.
Each lane in x is converted to the destination floating point format. This is an exact operation.
Since Cretonne currently only supports two floating point formats, this instruction always converts
f32
tof64
. This may change in the future.The result type must have the same number of vector lanes as the input, and the result lanes must be larger than the input lanes.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (FloatTo) – A scalar or vector floating point number
Type Variables:  FloatTo – explicitly provided
 Float – from input operand

a =
fdemote
x¶ Convert x to a smaller floating point format.
Each lane in x is converted to the destination floating point format by rounding to nearest, ties to even.
Since Cretonne currently only supports two floating point formats, this instruction always converts
f64
tof32
. This may change in the future.The result type must have the same number of vector lanes as the input, and the result lanes must be smaller than the input lanes.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (FloatTo) – A scalar or vector floating point number
Type Variables:  FloatTo – explicitly provided
 Float – from input operand

a =
fcvt_to_uint
x¶ Convert floating point to unsigned integer.
Each lane in x is converted to an unsigned integer by rounding towards zero. If x is NaN or if the unsigned integral value cannot be represented in the result type, this instruction traps.
The result type must have the same number of vector lanes as the input.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (IntTo) – A larger integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Float – from input operand

a =
fcvt_to_sint
x¶ Convert floating point to signed integer.
Each lane in x is converted to a signed integer by rounding towards zero. If x is NaN or if the signed integral value cannot be represented in the result type, this instruction traps.
The result type must have the same number of vector lanes as the input.
Arguments:  x (Float) – A scalar or vector floating point number
Results:  a (IntTo) – A larger integer type with the same number of lanes
Type Variables:  IntTo – explicitly provided
 Float – from input operand

a =
fcvt_from_uint
x¶ Convert unsigned integer to floating point.
Each lane in x is interpreted as an unsigned integer and converted to floating point using round to nearest, ties to even.
The result type must have the same number of vector lanes as the input.
Arguments:  x (Int) – A scalar or vector integer type
Results:  a (FloatTo) – A scalar or vector floating point number
Type Variables:  FloatTo – explicitly provided
 Int – from input operand

a =
fcvt_from_sint
x¶ Convert signed integer to floating point.
Each lane in x is interpreted as a signed integer and converted to floating point using round to nearest, ties to even.
The result type must have the same number of vector lanes as the input.
Arguments:  x (Int) – A scalar or vector integer type
Results:  a (FloatTo) – A scalar or vector floating point number
Type Variables:  FloatTo – explicitly provided
 Int – from input operand
Legalization operations¶
These instructions are used as helpers when legalizing types and operations for the target ISA.

lo, hi =
isplit
x¶ Split an integer into low and high parts.
Vectors of integers are split lanewise, so the results have the same number of lanes as the input, but the lanes are half the size.
Returns the low half of x and the high half of x as two independent values.
Arguments:  x (WideInt) – An integer type with lanes from i16 upwards
Results:  lo (half_width(WideInt)) – The low bits of x
 hi (half_width(WideInt)) – The high bits of x
Type Variables:  WideInt – inferred from x

a =
iconcat
lo, hi¶ Concatenate low and high bits to form a larger integer type.
Vectors of integers are concatenated lanewise such that the result has the same number of lanes as the inputs, but the lanes are twice the size.
Arguments:  lo (NarrowInt) – An integer type with lanes type to i32
 hi (NarrowInt) – An integer type with lanes type to i32
Results:  a (double_width(NarrowInt)) – The concatenation of lo and hi
Type Variables:  NarrowInt – inferred from lo
Base instruction group¶
All of the shared instructions are part of the base
instruction
group.

base.instructions.GROUP
Shared base instruction set
band
band_imm
bextend
bint
bitcast
bmask
bnot
bor
bor_imm
br_icmp
br_table
breduce
brnz
brz
bxor
bxor_imm
call
call_indirect
ceil
cls
clz
copy
ctz
extractlane
f32const
f64const
fabs
fadd
fallthrough
fcmp
fcopysign
fcvt_from_sint
fcvt_from_uint
fcvt_to_sint
fcvt_to_uint
fdemote
fdiv
fill
floor
fma
fmax
fmaxnum
fmin
fminnum
fmul
fneg
fpromote
fsub
heap_addr
heap_load
heap_store
iadd
iadd_carry
iadd_cin
iadd_cout
iadd_imm
icmp
icmp_imm
iconcat
iconst
imul
imul_imm
insertlane
ireduce
irsub_imm
ishl
ishl_imm
isplit
istore16
istore32
istore8
isub
isub_bin
isub_borrow
isub_bout
jump
load
nearest
popcnt
return
rotl
rotl_imm
rotr
rotr_imm
sdiv
sdiv_imm
select
sextend
sload16
sload32
sload8
spill
splat
sqrt
srem
srem_imm
sshr
sshr_imm
stack_addr
stack_load
stack_store
store
trap
trapnz
trapz
trunc
udiv
udiv_imm
uextend
uload16
uload32
uload8
urem
urem_imm
ushr
ushr_imm
vconcat
vselect
vsplit
Target ISAs may define further instructions in their own instruction groups.
Implementation limits¶
Cretonne’s intermediate representation imposes some limits on the size of functions and the number of entities allowed. If these limits are exceeded, the implementation will panic.
 Number of instructions in a function
 At most \(2^{31}  1\).
 Number of EBBs in a function
At most \(2^{31}  1\).
Every EBB needs at least a terminator instruction anyway.
 Number of secondary values in a function
At most \(2^{31}  1\).
Secondary values are any SSA values that are not the first result of an instruction.
 Other entities declared in the preamble
At most \(2^{32}  1\).
This covers things like stack slots, jump tables, external functions, and function signatures, etc.
 Number of arguments to an EBB
 At most \(2^{16}\).
 Number of arguments to a function
At most \(2^{16}\).
This follows from the limit on arguments to the entry EBB. Note that Cretonne may add a handful of ABI register arguments as function signatures are lowered. This is for representing things like the link register, the incoming frame pointer, and calleesaved registers that are saved in the prologue.
 Size of function call arguments on the stack
At most \(2^{32}  1\) bytes.
This is probably not possible to achieve given the limit on the number of arguments, except by requiring extremely large offsets for stack arguments.
Glossary¶
 intermediate language
 IL
 The language used to describe functions to Cretonne. This reference describes the syntax and semantics of the Cretonne IL. The IL has two forms: Textual and an inmemory intermediate representation (IR).
 intermediate representation
 IR
 The inmemory representation of IL. The data structures Cretonne uses to represent a program internally are called the intermediate representation. Cretonne’s IR can be converted to text losslessly.
 function signature
A function signature describes how to call a function. It consists of:
 The calling convention.
 The number of arguments and return values. (Functions can return multiple values.)
 Type and flags of each argument.
 Type and flags of each return value.
Not all function attributes are part of the signature. For example, a function that never returns could be marked as
noreturn
, but that is not necessary to know when calling it, so it is just an attribute, and not part of the signature. function preamble
A list of declarations of entities that are used by the function body. Some of the entities that can be declared in the preamble are:
 Local variables.
 Functions that are called directly.
 Function signatures for indirect function calls.
 Function flags and attributes that are not part of the signature.
 function body
 The extended basic blocks which contain all the executable code in a function. The function body follows the function preamble.
 basic block
 A maximal sequence of instructions that can only be entered from the top, and that contains no branch or terminator instructions except for the last instruction.
 extended basic block
 EBB
A maximal sequence of instructions that can only be entered from the top, and that contains no terminator instructions except for the last one. An EBB can contain conditional branches that can fall through to the following instructions in the block, but only the first instruction in the EBB can be a branch target.
The last instruction in an EBB must be a terminator instruction, so execution cannot flow through to the next EBB in the function. (But there may be a branch to the next EBB.)
Note that some textbooks define an EBB as a maximal subtree in the control flow graph where only the root can be a join node. This definition is not equivalent to Cretonne EBBs.
 terminator instruction
A control flow instruction that unconditionally directs the flow of execution somewhere else. Execution never continues at the instruction following a terminator instruction.
The basic terminator instructions are
br
,return
, andtrap
. Conditional branches and instructions that trap conditionally are not terminator instructions. entry block
 The EBB that is executed first in a function. Currently, a Cretonne function must have exactly one entry block which must be the first block in the function. The types of the entry block arguments must match the types of arguments in the function signature.
 stack slot
 A fixed size memory allocation in the current function’s activation frame. Also called a local variable.