## Compiler {#compiler}

## Assembler {#assembler}

// license that can be found in the LICENSE file.

// This file encapsulates some of the odd characteristics of the
// s390x instruction set, to minimize its interaction
// with the core of the assembler.

package arch

import (
	"cmd/internal/obj/s390x"
)

func jumpS390x(word string) bool {
	switch word {
	case "BRC",
		"BC",
		"BCL",
		"BEQ",
		"BGE",
		"BGT",
		"BL",
		"BLE",

// license that can be found in the LICENSE file.

// This file encapsulates some of the odd characteristics of the
// 64-bit PowerPC (PPC64) instruction set, to minimize its interaction
// with the core of the assembler.

package arch

import (
	"cmd/internal/obj"
	"cmd/internal/obj/ppc64"
)

func jumpPPC64(word string) bool {
	switch word {

	MOVQ DR7, SI // 0f21fe
	// Test other movtab entries.
	PUSHQ GS // 0fa8
	PUSHQ FS // 0fa0
	POPQ FS  // 0fa1
	POPQ GS  // 0fa9
	// All instructions below semantically have unsigned operands,
	// but previous assembler permitted negative arguments.
	// This behavior is preserved for compatibility reasons.
	VPSHUFD $-79, X7, X7         // c5f970ffb1
	RORXL $-1, (AX), DX          // c4e37bf010ff
	RORXQ $-1, (AX), DX          // c4e3fbf010ff

Previously, large builds could see 100%+ build time increase from enabling PGO.
In Go 1.23, overhead should be in the single digit percentages.

## Assembler {#assembler}

<!--{
	"Title": "A Quick Guide to Go's Assembler",
	"Path":  "/doc/asm"
}-->

<h2 id="introduction">A Quick Guide to Go's Assembler</h2>

<p>
This document is a quick outline of the unusual form of assembly language used by the <code>gc</code> Go compiler.
The document is not comprehensive.
</p>

<p>
The assembler is based on the input style of the Plan 9 assemblers, which is documented in detail

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package flags implements top-level flags and the usage message for the assembler.
package flags

import (
	"cmd/internal/obj"
	"cmd/internal/objabi"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

var (

// license that can be found in the LICENSE file.

// This file encapsulates some of the odd characteristics of the RISCV64
// instruction set, to minimize its interaction with the core of the
// assembler.

package arch

import (
	"cmd/internal/obj"
	"cmd/internal/obj/riscv"
)

// IsRISCV64AMO reports whether the op (as defined by a riscv.A*
// constant) is one of the AMO instructions that requires special

does not exist, <code>delete</code> is a no-op.
</p>


<h3 id="Complex_numbers">Manipulating complex numbers</h3>

<p>
Three functions assemble and disassemble complex numbers.
The built-in function <code>complex</code> constructs a complex
value from a floating-point real and imaginary part, while
<code>real</code> and <code>imag</code>

// This input was created by taking the instruction productions in
// the old assembler's (8a's) grammar and hand-writing complete
// instructions for each rule, to guarantee we cover the same space.

#include "../../../../../runtime/textflag.h"

TEXT foo(SB), DUPOK|NOSPLIT, $0

// LTYPE1 nonrem	{ outcode(int($1), &$2); }
	SETCC	AX
	SETCC	foo+4(SB)

// LTYPE2 rimnon	{ outcode(int($1), &$2); }
	DIVB	AX
	DIVB	foo+4(SB)
	PUSHL	$foo+4(SB)