Syntax of AMDGPU Instruction Operands¶
Conventions¶
The following notation is used throughout this document:
Notation
Description
{0..N}
Any integer value in the range from 0 to N (inclusive).
<x>
Syntax and meaning of x is explained elsewhere.
Operands¶
v¶
Vector registers. There are 256 32-bit vector registers.
A sequence of vector registers may be used to operate with more than 32 bits of data.
Assembler currently supports sequences of 1, 2, 3, 4, 5, 6, 7, 8, 16 and 32 vector registers.
Syntax
Description
v<N>
A single 32-bit vector register.
N must be a decimal integer number.
v[<N>]
A single 32-bit vector register.
N may be specified as an integer number or an absolute expression.
v[<N>:<K>]
A sequence of (K-N+1) vector registers.
N and K may be specified as integer numbers or absolute expressions.
[v<N>, v<N+1>, … v<K>]
A sequence of (K-N+1) vector registers.
Register indices must be specified as decimal integer numbers.
Note: N and K must satisfy the following conditions:
N <= K.
0 <= N <= 255.
0 <= K <= 255.
K-N+1 must be equal to 1, 2, 3, 4, 5, 6, 7, 8, 16 or 32.
GFX90A has an additional alignment requirement: pairs of vector registers must be even-aligned (first register must be even).
Examples:
v255
v[0]
v[0:1]
v[1:1]
v[0:3]
v[2*2]
v[1-1:2-1]
[v252]
[v252,v253,v254,v255]
GFX10 Image instructions may use special NSA (Non-Sequential Address) syntax for image addresses:
Syntax
Description
[Vm, Vn, … Vk]
A sequence of 32-bit vector registers. Each register may be specified using syntax defined above.
In contrast with standard syntax, registers in NSA sequence are not required to have consecutive indices. Moreover, the same register may appear in the list more than once.
Examples:
[v32,v1,v[2]]
[v[32],v[1:1],[v2]]
[v4,v4,v4,v4]
a¶
Accumulator registers. There are 256 32-bit accumulator registers.
A sequence of accumulator registers may be used to operate with more than 32 bits of data.
Assembler currently supports sequences of 1, 2, 3, 4, 5, 6, 7, 8, 16 and 32 accumulator registers.
Syntax
An Alternative Syntax (SP3)
Description
a<N>
acc<N>
A single 32-bit accumulator register.
N must be a decimal integer number.
a[<N>]
acc[<N>]
A single 32-bit accumulator register.
N may be specified as an integer number or an absolute expression.
a[<N>:<K>]
acc[<N>:<K>]
A sequence of (K-N+1) accumulator registers.
N and K may be specified as integer numbers or absolute expressions.
[a<N>, a<N+1>, … a<K>]
[acc<N>, acc<N+1>, … acc<K>]
A sequence of (K-N+1) accumulator registers.
Register indices must be specified as decimal integer numbers.
Note: N and K must satisfy the following conditions:
N <= K.
0 <= N <= 255.
0 <= K <= 255.
K-N+1 must be equal to 1, 2, 3, 4, 5, 6, 7, 8, 16 or 32.
GFX90A has an additional alignment requirement: pairs of accumulator registers must be even-aligned (first register must be even).
Examples:
a255
a[0]
a[0:1]
a[1:1]
a[0:3]
a[2*2]
a[1-1:2-1]
[a252]
[a252,a253,a254,a255]
acc0
acc[1]
[acc250]
[acc2,acc3]
s¶
Scalar 32-bit registers. The number of available scalar registers depends on GPU:
GPU
Number of scalar registers
GFX7
104
GFX8
102
GFX9
102
GFX10
106
A sequence of scalar registers may be used to operate with more than 32 bits of data. Assembler currently supports sequences of 1, 2, 3, 4, 5, 6, 7, 8, 16 and 32 scalar registers.
Pairs of scalar registers must be even-aligned (first register must be even). Sequences of 4 and more scalar registers must be quad-aligned.
Syntax
Description
s<N>
A single 32-bit scalar register.
N must be a decimal integer number.
s[<N>]
A single 32-bit scalar register.
N may be specified as an integer number or an absolute expression.
s[<N>:<K>]
A sequence of (K-N+1) scalar registers.
N and K may be specified as integer numbers or absolute expressions.
[s<N>, s<N+1>, … s<K>]
A sequence of (K-N+1) scalar registers.
Register indices must be specified as decimal integer numbers.
Note: N and K must satisfy the following conditions:
N must be properly aligned based on sequence size.
N <= K.
0 <= N < SMAX, where SMAX is the number of available scalar registers.
0 <= K < SMAX, where SMAX is the number of available scalar registers.
K-N+1 must be equal to 1, 2, 3, 4, 5, 6, 7, 8, 16 or 32.
Examples:
s0
s[0]
s[0:1]
s[1:1]
s[0:3]
s[2*2]
s[1-1:2-1]
[s4]
[s4,s5,s6,s7]
Examples of scalar registers with an invalid alignment:
s[1:2]
s[2:5]
ttmp¶
Trap handler temporary scalar registers, 32-bits wide. The number of available ttmp registers depends on GPU:
GPU
Number of ttmp registers
GFX7
12
GFX8
12
GFX9
16
GFX10
16
A sequence of ttmp registers may be used to operate with more than 32 bits of data. Assembler currently supports sequences of 1, 2, 3, 4, 5, 6, 7, 8 and 16 ttmp registers.
Pairs of ttmp registers must be even-aligned (first register must be even). Sequences of 4 and more ttmp registers must be quad-aligned.
Syntax
Description
ttmp<N>
A single 32-bit ttmp register.
N must be a decimal integer number.
ttmp[<N>]
A single 32-bit ttmp register.
N may be specified as an integer number or an absolute expression.
ttmp[<N>:<K>]
A sequence of (K-N+1) ttmp registers.
N and K may be specified as integer numbers or absolute expressions.
[ttmp<N>, ttmp<N+1>, … ttmp<K>]
A sequence of (K-N+1) ttmp registers.
Register indices must be specified as decimal integer numbers.
Note: N and K must satisfy the following conditions:
N must be properly aligned based on sequence size.
N <= K.
0 <= N < TMAX, where TMAX is the number of available ttmp registers.
0 <= K < TMAX, where TMAX is the number of available ttmp registers.
K-N+1 must be equal to 1, 2, 3, 4, 5, 6, 7, 8 or 16.
Examples:
ttmp0
ttmp[0]
ttmp[0:1]
ttmp[1:1]
ttmp[0:3]
ttmp[2*2]
ttmp[1-1:2-1]
[ttmp4]
[ttmp4,ttmp5,ttmp6,ttmp7]
Examples of ttmp registers with an invalid alignment:
ttmp[1:2]
ttmp[2:5]
tba¶
Trap base address, 64-bits wide. Holds the pointer to the current trap handler program.
Syntax
Description
Availability
tba
64-bit trap base address register.
GFX7, GFX8
[tba]
64-bit trap base address register (an SP3 syntax).
GFX7, GFX8
[tba_lo,tba_hi]
64-bit trap base address register (an SP3 syntax).
GFX7, GFX8
High and low 32 bits of trap base address may be accessed as separate registers:
Syntax
Description
Availability
tba_lo
Low 32 bits of trap base address register.
GFX7, GFX8
tba_hi
High 32 bits of trap base address register.
GFX7, GFX8
[tba_lo]
Low 32 bits of trap base address register (an SP3 syntax).
GFX7, GFX8
[tba_hi]
High 32 bits of trap base address register (an SP3 syntax).
GFX7, GFX8
Note that tba, tba_lo and tba_hi are not accessible as assembler registers in GFX9 and GFX10, but tba is readable/writable with the help of s_get_reg and s_set_reg instructions.
tma¶
Trap memory address, 64-bits wide.
Syntax
Description
Availability
tma
64-bit trap memory address register.
GFX7, GFX8
[tma]
64-bit trap memory address register (an SP3 syntax).
GFX7, GFX8
[tma_lo,tma_hi]
64-bit trap memory address register (an SP3 syntax).
GFX7, GFX8
High and low 32 bits of trap memory address may be accessed as separate registers:
Syntax
Description
Availability
tma_lo
Low 32 bits of trap memory address register.
GFX7, GFX8
tma_hi
High 32 bits of trap memory address register.
GFX7, GFX8
[tma_lo]
Low 32 bits of trap memory address register (an SP3 syntax).
GFX7, GFX8
[tma_hi]
High 32 bits of trap memory address register (an SP3 syntax).
GFX7, GFX8
Note that tma, tma_lo and tma_hi are not accessible as assembler registers in GFX9 and GFX10, but tma is readable/writable with the help of s_get_reg and s_set_reg instructions.
flat_scratch¶
Flat scratch address, 64-bits wide. Holds the base address of scratch memory.
Syntax
Description
flat_scratch
64-bit flat scratch address register.
[flat_scratch]
64-bit flat scratch address register (an SP3 syntax).
[flat_scratch_lo,flat_scratch_hi]
64-bit flat scratch address register (an SP3 syntax).
High and low 32 bits of flat scratch address may be accessed as separate registers:
Syntax
Description
flat_scratch_lo
Low 32 bits of flat scratch address register.
flat_scratch_hi
High 32 bits of flat scratch address register.
[flat_scratch_lo]
Low 32 bits of flat scratch address register (an SP3 syntax).
[flat_scratch_hi]
High 32 bits of flat scratch address register (an SP3 syntax).
Note that flat_scratch, flat_scratch_lo and flat_scratch_hi are not accessible as assembler registers in GFX10, but flat_scratch is readable/writable with the help of s_get_reg and s_set_reg instructions.
xnack_mask¶
Xnack mask, 64-bits wide. Holds a 64-bit mask of which threads received an XNACK due to a vector memory operation.
Warning
GFX7 does not support xnack feature. For availability of this feature in other GPUs, refer this table.
Syntax
Description
xnack_mask
64-bit xnack mask register.
[xnack_mask]
64-bit xnack mask register (an SP3 syntax).
[xnack_mask_lo,xnack_mask_hi]
64-bit xnack mask register (an SP3 syntax).
High and low 32 bits of xnack mask may be accessed as separate registers:
Syntax
Description
xnack_mask_lo
Low 32 bits of xnack mask register.
xnack_mask_hi
High 32 bits of xnack mask register.
[xnack_mask_lo]
Low 32 bits of xnack mask register (an SP3 syntax).
[xnack_mask_hi]
High 32 bits of xnack mask register (an SP3 syntax).
Note that xnack_mask, xnack_mask_lo and xnack_mask_hi are not accessible as assembler registers in GFX10, but xnack_mask is readable/writable with the help of s_get_reg and s_set_reg instructions.
vcc¶
Vector condition code, 64-bits wide. A bit mask with one bit per thread; it holds the result of a vector compare operation.
Note that GFX10 H/W does not use high 32 bits of vcc in wave32 mode.
Syntax
Description
vcc
64-bit vector condition code register.
[vcc]
64-bit vector condition code register (an SP3 syntax).
[vcc_lo,vcc_hi]
64-bit vector condition code register (an SP3 syntax).
High and low 32 bits of vector condition code may be accessed as separate registers:
Syntax
Description
vcc_lo
Low 32 bits of vector condition code register.
vcc_hi
High 32 bits of vector condition code register.
[vcc_lo]
Low 32 bits of vector condition code register (an SP3 syntax).
[vcc_hi]
High 32 bits of vector condition code register (an SP3 syntax).
m0¶
A 32-bit memory register. It has various uses, including register indexing and bounds checking.
Syntax
Description
m0
A 32-bit memory register.
[m0]
A 32-bit memory register (an SP3 syntax).
exec¶
Execute mask, 64-bits wide. A bit mask with one bit per thread, which is applied to vector instructions and controls which threads execute and which ignore the instruction.
Note that GFX10 H/W does not use high 32 bits of exec in wave32 mode.
Syntax
Description
exec
64-bit execute mask register.
[exec]
64-bit execute mask register (an SP3 syntax).
[exec_lo,exec_hi]
64-bit execute mask register (an SP3 syntax).
High and low 32 bits of execute mask may be accessed as separate registers:
Syntax
Description
exec_lo
Low 32 bits of execute mask register.
exec_hi
High 32 bits of execute mask register.
[exec_lo]
Low 32 bits of execute mask register (an SP3 syntax).
[exec_hi]
High 32 bits of execute mask register (an SP3 syntax).
vccz¶
A single bit flag indicating that the vcc is all zeros.
Note: when GFX10 operates in wave32 mode, this register reflects state of vcc_lo.
execz¶
A single bit flag indicating that the exec is all zeros.
Note: when GFX10 operates in wave32 mode, this register reflects state of exec_lo.
lds_direct¶
A special operand which supplies a 32-bit value fetched from LDS memory using m0 as an address.
null¶
This is a special operand which may be used as a source or a destination.
When used as a destination, the result of the operation is discarded.
When used as a source, it supplies zero value.
GFX10 only.
Warning
Due to a H/W bug, this operand cannot be used with VALU instructions in first generation of GFX10.
inline constant¶
An inline constant is an integer or a floating-point value encoded as a part of an instruction. Compare inline constants with literals.
Inline constants include:
If a number may be encoded as either a literal or a constant, assembler selects the latter encoding as more efficient.
iconst¶
An integer number or an absolute expression encoded as an inline constant.
Only a small fraction of integer numbers may be encoded as inline constants. They are enumerated in the table below. Other integer numbers have to be encoded as literals.
Value
Note
{0..64}
Positive integer inline constants.
{-16..-1}
Negative integer inline constants.
Warning
GFX7 does not support inline constants for f16 operands.
fconst¶
A floating-point number encoded as an inline constant.
Only a small fraction of floating-point numbers may be encoded as inline constants. They are enumerated in the table below. Other floating-point numbers have to be encoded as literals.
Value
Note
Availability
0.0
The same as integer constant 0.
All GPUs
0.5
Floating-point constant 0.5
All GPUs
1.0
Floating-point constant 1.0
All GPUs
2.0
Floating-point constant 2.0
All GPUs
4.0
Floating-point constant 4.0
All GPUs
-0.5
Floating-point constant -0.5
All GPUs
-1.0
Floating-point constant -1.0
All GPUs
-2.0
Floating-point constant -2.0
All GPUs
-4.0
Floating-point constant -4.0
All GPUs
0.1592
1.0/(2.0*pi). Use only for 16-bit operands.
GFX8, GFX9, GFX10
0.15915494
1.0/(2.0*pi). Use only for 16- and 32-bit operands.
GFX8, GFX9, GFX10
0.15915494309189532
1.0/(2.0*pi).
GFX8, GFX9, GFX10
Warning
Floating-point inline constants cannot be used with 16-bit integer operands. Assembler will attempt to encode these values as literals.
Warning
GFX7 does not support inline constants for f16 operands.
ival¶
A symbolic operand encoded as an inline constant. These operands provide read-only access to H/W registers.
Syntax
Note
Availability
shared_base
Base address of shared memory region.
GFX9, GFX10
shared_limit
Address of the end of shared memory region.
GFX9, GFX10
private_base
Base address of private memory region.
GFX9, GFX10
private_limit
Address of the end of private memory region.
GFX9, GFX10
pops_exiting_wave_id
A dedicated counter for POPS.
GFX9, GFX10
literal¶
A literal is a 64-bit value encoded as a separate 32-bit dword in the instruction stream. Compare literals with inline constants.
If a number may be encoded as either a literal or an inline constant, assembler selects the latter encoding as more efficient.
Literals may be specified as integer numbers, floating-point numbers, absolute expressions or relocatable expressions.
An instruction may use only one literal but several operands may refer the same literal.
uimm8¶
A 8-bit integer number or an absolute expression. The value must be in the range 0..0xFF.
uimm32¶
A 32-bit integer number or an absolute expression. The value must be in the range 0..0xFFFFFFFF.
uimm20¶
A 20-bit integer number or an absolute expression.
The value must be in the range 0..0xFFFFF.
simm21¶
A 21-bit integer number or an absolute expression.
The value must be in the range -0x100000..0x0FFFFF.
Numbers¶
Integer Numbers¶
Integer numbers are 64 bits wide. They are converted to expected operand type as described here.
Integer numbers may be specified in binary, octal, hexadecimal and decimal formats:
Format
Syntax
Example
Decimal
[-]?[1-9][0-9]*
-1234
Binary
[-]?0b[01]+
0b1010
Octal
[-]?0[0-7]+
010
Hexadecimal
[-]?0x[0-9a-fA-F]+
0xff
[-]?[0x]?[0-9][0-9a-fA-F]*[hH]
0ffh
Floating-Point Numbers¶
All floating-point numbers are handled as double (64 bits wide). They are converted to expected operand type as described here.
Floating-point numbers may be specified in hexadecimal and decimal formats:
Format
Syntax
Examples
Note
Decimal
[-]?[0-9]*[.][0-9]*([eE][+-]?[0-9]*)?
-1.234, 234e2
Must include either a decimal separator or an exponent.
Hexadecimal
[-]0x[0-9a-fA-F]*(.[0-9a-fA-F]*)?[pP][+-]?[0-9a-fA-F]+
-0x1afp-10, 0x.1afp10
Expressions¶
An expression is evaluated to a 64-bit integer. Note that floating-point expressions are not supported.
There are two kinds of expressions:
Absolute Expressions¶
The value of an absolute expression does not change after program relocation. Absolute expressions must not include unassigned and relocatable values such as labels.
Absolute expressions are evaluated to 64-bit integer values and converted to expected operand type as described here.
Examples:
x = -1
y = x + 10
Relocatable Expressions¶
The value of a relocatable expression depends on program relocation.
Note that use of relocatable expressions is limited with branch targets and 32-bit integer operands.
A relocatable expression is evaluated to a 64-bit integer value which depends on operand kind and relocation type of symbol(s) used in the expression. For example, if an instruction refers a label, this reference is evaluated to an offset from the address after the instruction to the label address:
label:
v_add_co_u32_e32 v0, vcc, label, v1 // 'label' operand is evaluated to -4
Note that values of relocatable expressions are usually unknown at assembly time; they are resolved later by a linker and converted to expected operand type as described here.
Operands and Operations¶
Expressions are composed of 64-bit integer operands and operations. Operands include integer numbers and symbols.
Expressions may also use “.” which is a reference to the current PC (program counter).
Syntax of Expressions¶
Syntax of expressions is shown below:
expr ::= expr binop expr | primaryexpr ;
primaryexpr ::= '(' expr ')' | symbol | number | '.' | unop primaryexpr ;
binop ::= '&&'
| '||'
| '|'
| '^'
| '&'
| '!'
| '=='
| '!='
| '<>'
| '<'
| '<='
| '>'
| '>='
| '<<'
| '>>'
| '+'
| '-'
| '*'
| '/'
| '%' ;
unop ::= '~'
| '+'
| '-'
| '!' ;
Binary Operators¶
Binary operators are described in the following table. They operate on and produce 64-bit integers. Operators with higher priority are performed first.
Operator
Priority
Meaning
*
5
Integer multiplication.
/
5
Integer division.
%
5
Integer signed remainder.
+
4
Integer addition.
-
4
Integer subtraction.
<<
3
Integer shift left.
>>
3
Logical shift right.
==
2
Equality comparison.
!=
2
Inequality comparison.
<>
2
Inequality comparison.
<
2
Signed less than comparison.
<=
2
Signed less than or equal comparison.
>
2
Signed greater than comparison.
>=
2
Signed greater than or equal comparison.
|
1
Bitwise or.
^
1
Bitwise xor.
&
1
Bitwise and.
&&
0
Logical and.
||
0
Logical or.
Unary Operators¶
Unary operators are described in the following table. They operate on and produce 64-bit integers.
Operator
Meaning
!
Logical negation.
~
Bitwise negation.
+
Integer unary plus.
-
Integer unary minus.
Symbols¶
A symbol is a named 64-bit integer value, representing a relocatable address or an absolute (non-relocatable) number.
- Symbol names have the following syntax:
[a-zA-Z_.][a-zA-Z0-9_$.@]*
The table below provides several examples of syntax used for symbol definition.
Syntax
Meaning
.globl <S>
Declares a global symbol S without assigning it a value.
.set <S>, <E>
Assigns the value of an expression E to a symbol S.
<S> = <E>
Assigns the value of an expression E to a symbol S.
<S>:
Declares a label S and assigns it the current PC value.
A symbol may be used before it is declared or assigned; unassigned symbols are assumed to be PC-relative.
Additional information about symbols may be found here.
Type and Size Conversion¶
This section describes what happens when a 64-bit integer number, a floating-point number or an expression is used for an operand which has a different type or size.
Conversion of Integer Values¶
Instruction operands may be specified as 64-bit integer numbers or absolute expressions. These values are converted to the expected operand type using the following steps:
1. Validation. Assembler checks if the input value may be truncated without loss to the required truncation width (see the table below). There are two cases when this operation is enabled:
The truncated bits are all 0.
The truncated bits are all 1 and the value after truncation has its MSB bit set.
In all other cases assembler triggers an error.
2. Conversion. The input value is converted to the expected type as described in the table below. Depending on operand kind, this conversion is performed by either assembler or AMDGPU H/W (or both).
Expected type
Truncation Width
Conversion
Description
i16, u16, b16
16
num.u16
Truncate to 16 bits.
i32, u32, b32
32
num.u32
Truncate to 32 bits.
i64
32
{-1,num.i32}
Truncate to 32 bits and then sign-extend the result to 64 bits.
u64, b64
32
{0,num.u32}
Truncate to 32 bits and then zero-extend the result to 64 bits.
f16
16
num.u16
Use low 16 bits as an f16 value.
f32
32
num.u32
Use low 32 bits as an f32 value.
f64
32
{num.u32,0}
Use low 32 bits of the number as high 32 bits of the result; low 32 bits of the result are zeroed.
Examples of enabled conversions:
// GFX9
v_add_u16 v0, -1, 0 // src0 = 0xFFFF
v_add_f16 v0, -1, 0 // src0 = 0xFFFF (NaN)
//
v_add_u32 v0, -1, 0 // src0 = 0xFFFFFFFF
v_add_f32 v0, -1, 0 // src0 = 0xFFFFFFFF (NaN)
//
v_add_u16 v0, 0xff00, v0 // src0 = 0xff00
v_add_u16 v0, 0xffffffffffffff00, v0 // src0 = 0xff00
v_add_u16 v0, -256, v0 // src0 = 0xff00
//
s_bfe_i64 s[0:1], 0xffefffff, s3 // src0 = 0xffffffffffefffff
s_bfe_u64 s[0:1], 0xffefffff, s3 // src0 = 0x00000000ffefffff
v_ceil_f64_e32 v[0:1], 0xffefffff // src0 = 0xffefffff00000000 (-1.7976922776554302e308)
//
x = 0xffefffff //
s_bfe_i64 s[0:1], x, s3 // src0 = 0xffffffffffefffff
s_bfe_u64 s[0:1], x, s3 // src0 = 0x00000000ffefffff
v_ceil_f64_e32 v[0:1], x // src0 = 0xffefffff00000000 (-1.7976922776554302e308)
Examples of disabled conversions:
// GFX9
v_add_u16 v0, 0x1ff00, v0 // truncated bits are not all 0 or 1
v_add_u16 v0, 0xffffffffffff00ff, v0 // truncated bits do not match MSB of the result
Conversion of Floating-Point Values¶
Instruction operands may be specified as 64-bit floating-point numbers. These values are converted to the expected operand type using the following steps:
1. Validation. Assembler checks if the input f64 number can be converted to the required floating-point type (see the table below) without overflow or underflow. Precision lost is allowed. If this conversion is not possible, assembler triggers an error.
2. Conversion. The input value is converted to the expected type as described in the table below. Depending on operand kind, this is performed by either assembler or AMDGPU H/W (or both).
Expected type
Required FP Type
Conversion
Description
i16, u16, b16
f16
f16(num)
Convert to f16 and use bits of the result as an integer value. The value has to be encoded as a literal or an error occurs. Note that the value cannot be encoded as an inline constant.
i32, u32, b32
f32
f32(num)
Convert to f32 and use bits of the result as an integer value.
i64, u64, b64
-
-
Conversion disabled.
f16
f16
f16(num)
Convert to f16.
f32
f32
f32(num)
Convert to f32.
f64
f64
{num.u32.hi,0}
Use high 32 bits of the number as high 32 bits of the result; zero-fill low 32 bits of the result.
Note that the result may differ from the original number.
Examples of enabled conversions:
// GFX9
v_add_f16 v0, 1.0, 0 // src0 = 0x3C00 (1.0)
v_add_u16 v0, 1.0, 0 // src0 = 0x3C00
//
v_add_f32 v0, 1.0, 0 // src0 = 0x3F800000 (1.0)
v_add_u32 v0, 1.0, 0 // src0 = 0x3F800000
// src0 before conversion:
// 1.7976931348623157e308 = 0x7fefffffffffffff
// src0 after conversion:
// 1.7976922776554302e308 = 0x7fefffff00000000
v_ceil_f64 v[0:1], 1.7976931348623157e308
v_add_f16 v1, 65500.0, v2 // ok for f16.
v_add_f32 v1, 65600.0, v2 // ok for f32, but would result in overflow for f16.
Examples of disabled conversions:
// GFX9
v_add_f16 v1, 65600.0, v2 // overflow
Conversion of Relocatable Values¶
Relocatable expressions may be used with 32-bit integer operands and jump targets.
When the value of a relocatable expression is resolved by a linker, it is converted as needed and truncated to the operand size. The conversion depends on relocation type and operand kind.
For example, when a 32-bit operand of an instruction refers a relocatable expression expr, this reference is evaluated to a 64-bit offset from the address after the instruction to the address being referenced, counted in bytes. Then the value is truncated to 32 bits and encoded as a literal:
expr = .
v_add_co_u32_e32 v0, vcc, expr, v1 // 'expr' operand is evaluated to -4
// and then truncated to 0xFFFFFFFC
As another example, when a branch instruction refers a label, this reference is evaluated to an offset from the address after the instruction to the label address, counted in dwords. Then the value is truncated to 16 bits:
label:
s_branch label // 'label' operand is evaluated to -1 and truncated to 0xFFFF