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// Copyright 2014 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 ppc64asm
import (
"bytes"
"fmt"
"strings"
)
// GNUSyntax returns the GNU assembler syntax for the instruction, as defined by GNU binutils.
// This form typically matches the syntax defined in the Power ISA Reference Manual.
func GNUSyntax(inst Inst) string {
var buf bytes.Buffer
if inst.Op == 0 {
return "error: unkown instruction"
}
buf.WriteString(inst.Op.String())
sep := " "
for i, arg := range inst.Args[:] {
if arg == nil {
break
}
text := gnuArg(&inst, i, arg)
if text == "" {
continue
}
buf.WriteString(sep)
sep = ","
buf.WriteString(text)
}
return buf.String()
}
// gnuArg formats arg (which is the argIndex's arg in inst) according to GNU rules.
// NOTE: because GNUSyntax is the only caller of this func, and it receives a copy
// of inst, it's ok to modify inst.Args here.
func gnuArg(inst *Inst, argIndex int, arg Arg) string {
// special cases for load/store instructions
if _, ok := arg.(Offset); ok {
if argIndex+1 == len(inst.Args) || inst.Args[argIndex+1] == nil {
panic(fmt.Errorf("wrong table: offset not followed by register"))
}
}
switch arg := arg.(type) {
case Reg:
if isLoadStoreOp(inst.Op) && argIndex == 1 && arg == R0 {
return "0"
}
return arg.String()
case CondReg:
if arg == CR0 && strings.HasPrefix(inst.Op.String(), "cmp") {
return "" // don't show cr0 for cmp instructions
} else if arg >= CR0 {
return fmt.Sprintf("cr%d", int(arg-CR0))
}
bit := [4]string{"lt", "gt", "eq", "so"}[(arg-Cond0LT)%4]
if arg <= Cond0SO {
return bit
}
return fmt.Sprintf("4*cr%d+%s", int(arg-Cond0LT)/4, bit)
case Imm:
return fmt.Sprintf("%d", arg)
case SpReg:
return fmt.Sprintf("%d", int(arg))
case PCRel:
return fmt.Sprintf(".%+#x", int(arg))
case Label:
return fmt.Sprintf("%#x", uint32(arg))
case Offset:
reg := inst.Args[argIndex+1].(Reg)
removeArg(inst, argIndex+1)
if reg == R0 {
return fmt.Sprintf("%d(0)", int(arg))
}
return fmt.Sprintf("%d(r%d)", int(arg), reg-R0)
}
return fmt.Sprintf("???(%v)", arg)
}
// removeArg removes the arg in inst.Args[index].
func removeArg(inst *Inst, index int) {
for i := index; i < len(inst.Args); i++ {
if i+1 < len(inst.Args) {
inst.Args[i] = inst.Args[i+1]
} else {
inst.Args[i] = nil
}
}
}
// isLoadStoreOp returns true if op is a load or store instruction
func isLoadStoreOp(op Op) bool {
switch op {
case LBZ, LBZU, LBZX, LBZUX:
return true
case LHZ, LHZU, LHZX, LHZUX:
return true
case LHA, LHAU, LHAX, LHAUX:
return true
case LWZ, LWZU, LWZX, LWZUX:
return true
case LWA, LWAX, LWAUX:
return true
case LD, LDU, LDX, LDUX:
return true
case LQ:
return true
case STB, STBU, STBX, STBUX:
return true
case STH, STHU, STHX, STHUX:
return true
case STW, STWU, STWX, STWUX:
return true
case STD, STDU, STDX, STDUX:
return true
case STQ:
return true
case LHBRX, LWBRX, STHBRX, STWBRX:
return true
}
return false
}
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