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llvm-mirror/docs/AMDGPUOperandSyntax.rst
Dmitry Preobrazhensky 2911459942 [AMDGPU][MC][DOC] Updated AMD GPU assembler description. 
Minor bugfixing and improvements.

See bug 36572: https://bugs.llvm.org/show_bug.cgi?id=36572

llvm-svn: 350120
2018-12-28 11:48:23 +00:00

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=====================================
Syntax of AMDGPU Instruction Operands
=====================================
.. contents::
:local:
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.
=================== =============================================================================
.. _amdgpu_syn_operands:
Operands
========
.. _amdgpu_synid_v:
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, 8 and 16 *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
:ref:`integer number<amdgpu_synid_integer_number>`
or an :ref:`absolute expression<amdgpu_synid_absolute_expression>`.
**v[**\ <N>:<K>\ **]** A sequence of (\ *K-N+1*\ ) *vector* registers.
*N* and *K* may be specified as
:ref:`integer numbers<amdgpu_synid_integer_number>`
or :ref:`absolute expressions<amdgpu_synid_absolute_expression>`.
**[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, 8 or 16.
Examples:
.. parsed-literal::
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]
.. _amdgpu_synid_s:
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
======= ============================
A sequence of *scalar* registers may be used to operate with more than 32 bits of data.
Assembler currently supports sequences of 1, 2, 4, 8 and 16 *scalar* registers.
Pairs of *scalar* registers must be even-aligned (the 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
:ref:`integer number<amdgpu_synid_integer_number>`
or an :ref:`absolute expression<amdgpu_synid_absolute_expression>`.
**s[**\ <N>:<K>\ **]** A sequence of (\ *K-N+1*\ ) *scalar* registers.
*N* and *K* may be specified as
:ref:`integer numbers<amdgpu_synid_integer_number>`
or :ref:`absolute expressions<amdgpu_synid_absolute_expression>`.
**[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, 4, 8 or 16.
Examples:
.. parsed-literal::
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:
.. parsed-literal::
s[1:2]
s[2:5]
.. _amdgpu_synid_trap:
trap
----
A set of trap handler registers:
* :ref:`ttmp<amdgpu_synid_ttmp>`
* :ref:`tba<amdgpu_synid_tba>`
* :ref:`tma<amdgpu_synid_tma>`
.. _amdgpu_synid_ttmp:
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
======= ===========================
A sequence of *ttmp* registers may be used to operate with more than 32 bits of data.
Assembler currently supports sequences of 1, 2, 4, 8 and 16 *ttmp* registers.
Pairs of *ttmp* registers must be even-aligned (the 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
:ref:`integer number<amdgpu_synid_integer_number>`
or an :ref:`absolute expression<amdgpu_synid_absolute_expression>`.
**ttmp[**\ <N>:<K>\ **]** A sequence of (\ *K-N+1*\ ) *ttmp* registers.
*N* and *K* may be specified as
:ref:`integer numbers<amdgpu_synid_integer_number>`
or :ref:`absolute expressions<amdgpu_synid_absolute_expression>`.
**[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, 4, 8 or 16.
Examples:
.. parsed-literal::
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:
.. parsed-literal::
ttmp[1:2]
ttmp[2:5]
.. _amdgpu_synid_tba:
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 alternative syntax). GFX7, GFX8
[tba_lo,tba_hi] 64-bit *trap base address* register (an alternative 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 alternative syntax). GFX7, GFX8
[tba_hi] High 32 bits of *trap base address* register (an alternative syntax). GFX7, GFX8
================== ======================================================================= =============
Note that *tba*, *tba_lo* and *tba_hi* are not accessible as assembler registers in GFX9,
but *tba* is readable/writable with the help of *s_get_reg* and *s_set_reg* instructions.
.. _amdgpu_synid_tma:
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 alternative syntax). GFX7, GFX8
[tma_lo,tma_hi] 64-bit *trap memory address* register (an alternative 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 alternative syntax). GFX7, GFX8
[tma_hi] High 32 bits of *trap memory address* register (an alternative syntax). GFX7, GFX8
================= ======================================================================= ==================
Note that *tma*, *tma_lo* and *tma_hi* are not accessible as assembler registers in GFX9,
but *tma* is readable/writable with the help of *s_get_reg* and *s_set_reg* instructions.
.. _amdgpu_synid_flat_scratch:
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 alternative syntax).
[flat_scratch_lo,flat_scratch_hi] 64-bit *flat scratch* address register (an alternative 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 alternative syntax).
[flat_scratch_hi] High 32 bits of *flat scratch* address register (an alternative syntax).
========================= =========================================================================
.. _amdgpu_synid_xnack:
xnack
-----
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. Not all GFX8 and GFX9 :ref:`processors<amdgpu-processors>` support *xnack* feature.
\
============================== =====================================================
Syntax Description
============================== =====================================================
xnack_mask 64-bit *xnack mask* register.
[xnack_mask] 64-bit *xnack mask* register (an alternative syntax).
[xnack_mask_lo,xnack_mask_hi] 64-bit *xnack mask* register (an alternative 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 alternative syntax).
[xnack_mask_hi] High 32 bits of *xnack mask* register (an alternative syntax).
===================== ==============================================================
.. _amdgpu_synid_vcc:
vcc
---
Vector condition code, 64-bits wide. A bit mask with one bit per thread;
it holds the result of a vector compare operation.
================ =========================================================================
Syntax Description
================ =========================================================================
vcc 64-bit *vector condition code* register.
[vcc] 64-bit *vector condition code* register (an alternative syntax).
[vcc_lo,vcc_hi] 64-bit *vector condition code* register (an alternative 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 alternative syntax).
[vcc_hi] High 32 bits of *vector condition code* register (an alternative syntax).
================ =========================================================================
.. _amdgpu_synid_m0:
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 alternative syntax).
=========== ===================================================
.. _amdgpu_synid_exec:
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.
===================== =================================================================
Syntax Description
===================== =================================================================
exec 64-bit *execute mask* register.
[exec] 64-bit *execute mask* register (an alternative syntax).
[exec_lo,exec_hi] 64-bit *execute mask* register (an alternative 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 alternative syntax).
[exec_hi] High 32 bits of *execute mask* register (an alternative syntax).
===================== =================================================================
.. _amdgpu_synid_vccz:
vccz
----
A single bit-flag indicating that the :ref:`vcc<amdgpu_synid_vcc>` is all zeros.
.. WARNING:: This operand is not currently supported by AMDGPU assembler.
.. _amdgpu_synid_execz:
execz
-----
A single bit flag indicating that the :ref:`exec<amdgpu_synid_exec>` is all zeros.
.. WARNING:: This operand is not currently supported by AMDGPU assembler.
.. _amdgpu_synid_scc:
scc
---
A single bit flag indicating the result of a scalar compare operation.
.. WARNING:: This operand is not currently supported by AMDGPU assembler.
lds_direct
----------
A special operand which supplies a 32-bit value
fetched from *LDS* memory using :ref:`m0<amdgpu_synid_m0>` as an address.
.. WARNING:: This operand is not currently supported by AMDGPU assembler.
.. _amdgpu_synid_constant:
constant
--------
A set of integer and floating-point *inline constants*:
* :ref:`iconst<amdgpu_synid_iconst>`
* :ref:`fconst<amdgpu_synid_fconst>`
These operands are encoded as a part of instruction.
If a number may be encoded as either
a :ref:`literal<amdgpu_synid_literal>` or
an :ref:`inline constant<amdgpu_synid_constant>`,
assembler selects the latter encoding as more efficient.
.. _amdgpu_synid_iconst:
iconst
------
An :ref:`integer number<amdgpu_synid_integer_number>`
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 :ref:`literals<amdgpu_synid_literal>`.
Integer *inline constants* are converted to
:ref:`expected operand type<amdgpu_syn_instruction_type>`
as described :ref:`here<amdgpu_synid_int_const_conv>`.
================================== ====================================
Value Note
================================== ====================================
{0..64} Positive integer inline constants.
{-16..-1} Negative integer inline constants.
================================== ====================================
.. WARNING:: GFX7 does not support inline constants for *f16* operands.
There are also symbolic inline constants which provide read-only access to H/W registers.
.. WARNING:: These inline constants are not currently supported by AMDGPU assembler.
\
======================== ================================================ =============
Syntax Note Availability
======================== ================================================ =============
shared_base Base address of shared memory region. GFX9
shared_limit Address of the end of shared memory region. GFX9
private_base Base address of private memory region. GFX9
private_limit Address of the end of private memory region. GFX9
pops_exiting_wave_id A dedicated counter for POPS. GFX9
======================== ================================================ =============
.. _amdgpu_synid_fconst:
fconst
------
A :ref:`floating-point number<amdgpu_synid_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 :ref:`literals<amdgpu_synid_literal>`.
Floating-point *inline constants* are converted to
:ref:`expected operand type<amdgpu_syn_instruction_type>`
as described :ref:`here<amdgpu_synid_fp_const_conv>`.
================================== ===================================================== ==================
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
0.15915494 1.0/(2.0*pi). Use only for 16- and 32-bit operands. GFX8, GFX9
0.159154943091895317852646485335 1.0/(2.0*pi). GFX8, GFX9
================================== ===================================================== ==================
.. WARNING:: GFX7 does not support inline constants for *f16* operands.
.. _amdgpu_synid_literal:
literal
-------
A literal is a 64-bit value which is encoded as a separate 32-bit dword in the instruction stream.
If a number may be encoded as either
a :ref:`literal<amdgpu_synid_literal>` or
an :ref:`inline constant<amdgpu_synid_constant>`,
assembler selects the latter encoding as more efficient.
Literals may be specified as :ref:`integer numbers<amdgpu_synid_integer_number>`,
:ref:`floating-point numbers<amdgpu_synid_floating-point_number>` or
:ref:`expressions<amdgpu_synid_expression>`
(expressions are currently supported for 32-bit operands only).
A 64-bit literal value is converted by assembler
to an :ref:`expected operand type<amdgpu_syn_instruction_type>`
as described :ref:`here<amdgpu_synid_lit_conv>`.
An instruction may use only one literal but several operands may refer the same literal.
.. _amdgpu_synid_uimm8:
uimm8
-----
A 8-bit positive :ref:`integer number<amdgpu_synid_integer_number>`.
The value is encoded as part of the opcode so it is free to use.
.. _amdgpu_synid_uimm32:
uimm32
------
A 32-bit positive :ref:`integer number<amdgpu_synid_integer_number>`.
The value is stored as a separate 32-bit dword in the instruction stream.
.. _amdgpu_synid_uimm20:
uimm20
------
A 20-bit positive :ref:`integer number<amdgpu_synid_integer_number>`.
.. _amdgpu_synid_uimm21:
uimm21
------
A 21-bit positive :ref:`integer number<amdgpu_synid_integer_number>`.
.. WARNING:: Assembler currently supports 20-bit offsets only. Use :ref:`uimm20<amdgpu_synid_uimm20>` as a replacement.
.. _amdgpu_synid_simm21:
simm21
------
A 21-bit :ref:`integer number<amdgpu_synid_integer_number>`.
.. WARNING:: Assembler currently supports 20-bit unsigned offsets only .Use :ref:`uimm20<amdgpu_synid_uimm20>` as a replacement.
.. _amdgpu_synid_off:
off
---
A special entity which indicates that the value of this operand is not used.
================================== ===================================================
Syntax Description
================================== ===================================================
off Indicates an unused operand.
================================== ===================================================
.. _amdgpu_synid_number:
Numbers
=======
.. _amdgpu_synid_integer_number:
Integer Numbers
---------------
Integer numbers are 64 bits wide.
They may be specified in binary, octal, hexadecimal and decimal formats:
============== ====================================
Format Syntax
============== ====================================
Decimal [-]?[1-9][0-9]*
Binary [-]?0b[01]+
Octal [-]?0[0-7]+
Hexadecimal [-]?0x[0-9a-fA-F]+
\ [-]?[0x]?[0-9][0-9a-fA-F]*[hH]
============== ====================================
Examples:
.. parsed-literal::
-1234
0b1010
010
0xff
0ffh
.. _amdgpu_synid_floating-point_number:
Floating-Point Numbers
----------------------
All floating-point numbers are handled as double (64 bits wide).
Floating-point numbers may be specified in hexadecimal and decimal formats:
============== ======================================================== ========================================================
Format Syntax Note
============== ======================================================== ========================================================
Decimal [-]?[0-9]*[.][0-9]*([eE][+-]?[0-9]*)? Must include either a decimal separator or an exponent.
Hexadecimal [-]0x[0-9a-fA-F]*(.[0-9a-fA-F]*)?[pP][+-]?[0-9a-fA-F]+
============== ======================================================== ========================================================
Examples:
.. parsed-literal::
-1.234
234e2
-0x1afp-10
0x.1afp10
.. _amdgpu_synid_expression:
Expressions
===========
An expression specifies an address or a numeric value.
There are two kinds of expressions:
* :ref:`Absolute<amdgpu_synid_absolute_expression>`.
* :ref:`Relocatable<amdgpu_synid_relocatable_expression>`.
.. _amdgpu_synid_absolute_expression:
Absolute Expressions
--------------------
The value of an absolute expression remains the same after program relocation.
Absolute expressions must not include unassigned and relocatable values
such as labels.
Examples:
.. parsed-literal::
x = -1
y = x + 10
.. _amdgpu_synid_relocatable_expression:
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 :ref:`literals<amdgpu_synid_literal>`.
Addition information about relocation may be found :ref:`here<amdgpu-relocation-records>`.
Examples:
.. parsed-literal::
y = x + 10 // x is not yet defined. Undefined symbols are assumed to be PC-relative.
z = .
Expression Data Type
--------------------
Expressions and operands of expressions are interpreted as 64-bit integers.
Expressions may include 64-bit :ref:`floating-point numbers<amdgpu_synid_floating-point_number>` (double).
However these operands are also handled as 64-bit integers
using binary representation of specified floating-point numbers.
No conversion from floating-point to integer is performed.
Examples:
.. parsed-literal::
x = 0.1 // x is assigned an integer 4591870180066957722 which is a binary representation of 0.1.
y = x + x // y is a sum of two integer values; it is not equal to 0.2!
Syntax
------
Expressions are composed of
:ref:`symbols<amdgpu_synid_symbol>`,
:ref:`integer numbers<amdgpu_synid_integer_number>`,
:ref:`floating-point numbers<amdgpu_synid_floating-point_number>`,
:ref:`binary operators<amdgpu_synid_expression_bin_op>`,
:ref:`unary operators<amdgpu_synid_expression_un_op>` and subexpressions.
Expressions may also use "." which is a reference to the current PC (program counter).
The syntax of expressions is shown below::
expr ::= expr binop expr | primaryexpr ;
primaryexpr ::= '(' expr ')' | symbol | number | '.' | unop primaryexpr ;
binop ::= '&&'
| '||'
| '|'
| '^'
| '&'
| '!'
| '=='
| '!='
| '<>'
| '<'
| '<='
| '>'
| '>='
| '<<'
| '>>'
| '+'
| '-'
| '*'
| '/'
| '%' ;
unop ::= '~'
| '+'
| '-'
| '!' ;
.. _amdgpu_synid_expression_bin_op:
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.
========== ========= ===============================================
.. _amdgpu_synid_expression_un_op:
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.
========== ===============================================
.. _amdgpu_synid_symbol:
Symbols
-------
A symbol is a named 64-bit 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.
Addition information about symbols may be found :ref:`here<amdgpu-symbols>`.
.. _amdgpu_synid_conv:
Conversions
===========
This section describes what happens when a 64-bit
:ref:`integer number<amdgpu_synid_integer_number>`, a
:ref:`floating-point numbers<amdgpu_synid_floating-point_number>` or a
:ref:`symbol<amdgpu_synid_symbol>`
is used for an operand which has a different type or size.
Depending on operand kind, this conversion is performed by either assembler or AMDGPU H/W:
* Values encoded as :ref:`inline constants<amdgpu_synid_constant>` are handled by H/W.
* Values encoded as :ref:`literals<amdgpu_synid_literal>` are converted by assembler.
.. _amdgpu_synid_const_conv:
Inline Constants
----------------
.. _amdgpu_synid_int_const_conv:
Integer Inline Constants
~~~~~~~~~~~~~~~~~~~~~~~~
Integer :ref:`inline constants<amdgpu_synid_constant>`
may be thought of as 64-bit
:ref:`integer numbers<amdgpu_synid_integer_number>`;
when used as operands they are truncated to the size of
:ref:`expected operand type<amdgpu_syn_instruction_type>`.
No data type conversions are performed.
Examples:
.. parsed-literal::
// GFX9
v_add_u16 v0, -1, 0 // v0 = 0xFFFF
v_add_f16 v0, -1, 0 // v0 = 0xFFFF (NaN)
v_add_u32 v0, -1, 0 // v0 = 0xFFFFFFFF
v_add_f32 v0, -1, 0 // v0 = 0xFFFFFFFF (NaN)
.. _amdgpu_synid_fp_const_conv:
Floating-Point Inline Constants
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Floating-point :ref:`inline constants<amdgpu_synid_constant>`
may be thought of as 64-bit
:ref:`floating-point numbers<amdgpu_synid_floating-point_number>`;
when used as operands they are converted to a floating-point number of
:ref:`expected operand size<amdgpu_syn_instruction_type>`.
Examples:
.. parsed-literal::
// GFX9
v_add_f16 v0, 1.0, 0 // v0 = 0x3C00 (1.0)
v_add_u16 v0, 1.0, 0 // v0 = 0x3C00
v_add_f32 v0, 1.0, 0 // v0 = 0x3F800000 (1.0)
v_add_u32 v0, 1.0, 0 // v0 = 0x3F800000
.. _amdgpu_synid_lit_conv:
Literals
--------
.. _amdgpu_synid_int_lit_conv:
Integer Literals
~~~~~~~~~~~~~~~~
Integer :ref:`literals<amdgpu_synid_literal>`
are specified as 64-bit :ref:`integer numbers<amdgpu_synid_integer_number>`.
When used as operands they are converted to
:ref:`expected operand type<amdgpu_syn_instruction_type>` as described below.
============== ============== =============== ====================================================================
Expected type Condition Result Note
============== ============== =============== ====================================================================
i16, u16, b16 cond(num,16) num.u16 Truncate to 16 bits.
i32, u32, b32 cond(num,32) num.u32 Truncate to 32 bits.
i64 cond(num,32) {-1,num.i32} Truncate to 32 bits and then sign-extend the result to 64 bits.
u64, b64 cond(num,32) { 0,num.u32} Truncate to 32 bits and then zero-extend the result to 64 bits.
f16 cond(num,16) num.u16 Use low 16 bits as an f16 value.
f32 cond(num,32) num.u32 Use low 32 bits as an f32 value.
f64 cond(num,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.
============== ============== =============== ====================================================================
The condition *cond(X,S)* indicates if a 64-bit number *X*
can be converted to a smaller size *S* by truncation of upper bits.
There are two cases when the conversion is possible:
* The truncated bits are all 0.
* The truncated bits are all 1 and the value after truncation has its MSB bit set.
Examples of valid literals:
.. parsed-literal::
// GFX9
// Literal value after conversion:
v_add_u16 v0, 0xff00, v0 // 0xff00
v_add_u16 v0, 0xffffffffffffff00, v0 // 0xff00
v_add_u16 v0, -256, v0 // 0xff00
// Literal value after conversion:
s_bfe_i64 s[0:1], 0xffefffff, s3 // 0xffffffffffefffff
s_bfe_u64 s[0:1], 0xffefffff, s3 // 0x00000000ffefffff
v_ceil_f64_e32 v[0:1], 0xffefffff // 0xffefffff00000000 (-1.7976922776554302e308)
Examples of invalid literals:
.. parsed-literal::
// 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
.. _amdgpu_synid_fp_lit_conv:
Floating-Point Literals
~~~~~~~~~~~~~~~~~~~~~~~
Floating-point :ref:`literals<amdgpu_synid_literal>` are specified as 64-bit
:ref:`floating-point numbers<amdgpu_synid_floating-point_number>`.
When used as operands they are converted to
:ref:`expected operand type<amdgpu_syn_instruction_type>` as described below.
============== ============== ================= =================================================================
Expected type Condition Result Note
============== ============== ================= =================================================================
i16, u16, b16 cond(num,16) f16(num) Convert to f16 and use bits of the result as an integer value.
i32, u32, b32 cond(num,32) f32(num) Convert to f32 and use bits of the result as an integer value.
i64, u64, b64 false \- Conversion disabled because of an unclear semantics.
f16 cond(num,16) f16(num) Convert to f16.
f32 cond(num,32) f32(num) Convert to f32.
f64 true {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.
============== ============== ================= =================================================================
The condition *cond(X,S)* indicates if an f64 number *X* can be converted
to a smaller *S*-bit floating-point type without overflow or underflow.
Precision lost is allowed.
Examples of valid literals:
.. parsed-literal::
// GFX9
v_add_f16 v1, 65500.0, v2
v_add_f32 v1, 65600.0, v2
// Literal value before conversion: 1.7976931348623157e308 (0x7fefffffffffffff)
// Literal value after conversion: 1.7976922776554302e308 (0x7fefffff00000000)
v_ceil_f64 v[0:1], 1.7976931348623157e308
Examples of invalid literals:
.. parsed-literal::
// GFX9
v_add_f16 v1, 65600.0, v2 // overflow
.. _amdgpu_synid_exp_conv:
Expressions
~~~~~~~~~~~
Expressions operate with and result in 64-bit integers.
When used as operands they are truncated to
:ref:`expected operand size<amdgpu_syn_instruction_type>`.
No data type conversions are performed.
Examples:
.. parsed-literal::
// GFX9
x = 0.1
v_sqrt_f32 v0, x // v0 = [low 32 bits of 0.1 (double)]
v_sqrt_f32 v0, (0.1 + 0) // the same as above
v_sqrt_f32 v0, 0.1 // v0 = [0.1 (double) converted to float]
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