wiki:ClrxAsmSyntax

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CLRadeonExtender Assembler syntax

The CLRX assembler is compatible with GNU as syntax. In the many cases code for GNU as can be easily ported to CLRX assembler, ofcourse except processor instructions.

Layout of the source

The assembler accepts plain text that contains lines. Lines contains one of more statements. Statement can be the symbol's assignment, assembler's pseudo-operation (directive) or processor's instruction.

Pseudo-operations begins from . character. Symbol assignment is in following form: symbolName=expression.

If line is too long, it can be splitted into small parts by using \ at end of line, likewise as in C/C++ language.

Statement can be separated in single line by semicolon ;. Like that:

.int 1,2,3; v_nop; nop_count = nop_count+1

Single comment begins from #. Multiline comment is same as in C/C++ language: begins from /* and terminates at */.

Names of pseudo-operations, macro names, processors instructions and other names (for example: argument type, gpu device type) are case-insensitive. Symbol names are case-sensitive.

Symbols

CRLX assembler operates on the symbols. The symbol is value that can be a absolute value or it can refer to some place in binary code. Special symbol that is always defined refers to current place of a binary code. This is . and is called in this manual as output counter. Symbol names can contains alphanumeric characters, . and _. First character must not be a digit. This same rules concerns a labels.

Label are symbol that can not be redefined. Labels precedes statement and can occurred many times. Like that:

label1: init: v_add_i32 v1, v2 end: s_endpgm

Special kind of the label is local labels. They can be used only locally. The identifier of local labels can have only digits. In contrast, local labels can to be redefined many times. In source code reference can be to previous or next local label by adding b or f suffix.

v_add_i32 v32,3f-3b,v2 # 3b is previous `3` label, 3f is next `3` label

CLRX assembler accepts assignment register or register's range to symbols. Register or register's range shall to be preceded by '%' at assignment. Register symbol can be used for instruction operand or other register assignment. Register subranges or just single register can be extracted from parent register ranges by using indexing as well as regular register pools. Example:

regpool = %v[16:31] reg1 = %s[0:1] s_and_b64 reg1, s[2:3], s[4:5] # output as s[0:1] s_cmp_lt_i32 reg1[0], s2 # compare s0 with s2 v_xor_b32 regpool[4], regpool[7], regpool[9] # v_xor_b32 v20, v23, v25 zx = 10 # zx symbol v_xor_b32 regpool[zx+1], regpool[zx+5], regpool[zx+7] # v_xor_b32 v27, v31, v33

Sections

Section is some part of the binary that contains some data. Type of the data depends on type of the section. Main program code is in the .text section which holds program's instructions. Section .rodata holds read-only data (mainly constant data) that can be used by program. Section can be divided by type of the access. The most sections are writeable (any data can be put into them) and addressable (we can define symbols inside these sections or move forward).

Absolute section is only addressable section. It can be used for defining structures. In absolute section output counter can be moved backward (this is special exception for absolute section).

Any symbol that refer to some code place refer to sections.

Literals

CLRX assembler treats any constant literals as 64-bit value. Assembler honors C/C++ literal syntax. Special kind of literal are floating point literals. They can be used only in .half, .single, .float, .double pseudo-operations or as operand of the instruction that accepts floating point literals.

Literal types:

  • decimal literals: 100, 12, 4323
  • hexadecimal literals: 0x354, 0x3da, 0xDAB
  • octal literals: 0246, 077
  • binary literals: 0b10010101, 0b11011
  • character literals: 'a', 'b', '-', '\n', '\t', '\v', '\xab', '\123
  • floating point literals: 10.2, .45, +1.5e, 100e-6, 0x1a2.4b5p5
  • string literals: `"ala ma kota", "some\n"

For character literals and string literals, escape can be used to put special characters likes newline, tab. List of the escapes:

Escape Description Value
\a Alarm 7
\b Backspace 8
\t Tab 9
\n Newline 10
\v Vertical tab 11
\f Form feed 12
\r Carriage return 13
\\ Backslash 92
\" Double-quote 34
\' Qoute 39
\aaa Octal code Various
\HHH.. Hexadecimal code Various

Expressions

The CLRX assembler get this same the operator ordering as in GNU as. CLRX assembler treat any literal or symbol's value as 64-bit integer value. List of the operators:

Type Operator Order Description
Unary - 1 Negate value
Unary ~ 1 Binary NOT
Unary ! 1 Logical NOT
Unary + 1 Plus (doing nothing)
Binary * 2 Multiplication
Binary / 2 Signed division
Binary // 2 Unsigned division
Binary % 2 Signed remainder
Binary %% 2 Unsigned remainder
Binary << 2 Left shift
Binary >> 2 Unsigned right shift
Binary >>> 2 Signed right shift
Binary & 3 Binary AND
Binary vert-line 3 Binary OR
Binary ^ 3 Binary XOR
Binary ! 3 Binary ORNOT (performs A
Binary + 3 Addition
Binary - 3 Subtraction
Binary == 4 Equal to
Binary !=,<> 4 Not equal to
Binary < 4 Less than (signed)
Binary <= 4 Less or equal (signed)
Binary > 4 Greater than (signed)
Binary >= 4 Greater or equal (signed)
Binary <@ 4 Less than (unsigned)
Binary <=@ 4 Less or equal (unsigned)
Binary >@ 4 Greater than (unsigned)
Binary >=@ 4 Greater or equal (unsigned)
Binary && 5 Logical AND
Binary dbl-vert-line 5 Logical OR
Binary ?: 6 Choice (this same as C++)

'vert-line' is |, and 'dbl-vert-line' is ||.

The ?: operator have this same meanigful as in C/C++ and performed from right to left side.

Important note: Comparison operators return all ones (-1) value instead 1.

Symbol refering to some place can be added, subtracted, compared or negated if final result of the expression can be represented as place of the code or absolute value (without refering to any place). An assembler performs this same operations on the sections during evaluating an expression. Division, modulo, binary operations (except negation), logical operations is not legal.

Instruction operands

Instruction operand can be one of list:

  • GCN register or register range
  • absolute expression
  • float literal
  • in VOP3 encoding operand modifier: abs, neg

An expression can be preceded by '@' to ensure that a following text will be treated as an expression:

v_add_f32 v0, @v0, v4 # second operand is expression: 'v0' instead of v0 register

Alternatively, any expression can be inscribed in parentheses to ensure that result.