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cmd/internal/obj/arm64: improve comment and signature of pcAlignPadLength

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The function just calculates the number of needed padding bytes,
instead of actually carrying out the alignment operation. And it has
the context argument at the end of the argument list, while contexts
idiomatically come first. Indeed, this is the only case in
cmd/internal/obj where ctxt is not the only argument and does not come
first.

Fix those two nits; no functional change intended.

Suggested by Ian during review of CL 479815 (that introduces a copy of
this helper into the loong64 port).

Change-Id: Ieb221ead23282abe6e04804d537e1234c7ab21d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/483155
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
WANG Xuerui 2023-04-08 02:06:18 +08:00 committed by Eric Fang
parent f00c54146c
commit 58eaecbf9a
1 changed files with 6 additions and 5 deletions
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11
src/cmd/internal/obj/arm64/asm7.go
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@ -1015,8 +1015,9 @@ var sysInstFields = map[SpecialOperand]struct {
// Used for padding NOOP instruction
const OP_NOOP = 0xd503201f
// align code to a certain length by padding bytes.
func pcAlignPadLength(pc int64, alignedValue int64, ctxt *obj.Link) int {
// pcAlignPadLength returns the number of bytes required to align pc to alignedValue,
// reporting an error if alignedValue is not a power of two or is out of range.
func pcAlignPadLength(ctxt *obj.Link, pc int64, alignedValue int64) int {
if !((alignedValue&(alignedValue-1) == 0) && 8 <= alignedValue && alignedValue <= 2048) {
ctxt.Diag("alignment value of an instruction must be a power of two and in the range [8, 2048], got %d\n", alignedValue)
}
@ -1075,7 +1076,7 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
switch p.As {
case obj.APCALIGN:
alignedValue := p.From.Offset
m = pcAlignPadLength(pc, alignedValue, ctxt)
m = pcAlignPadLength(ctxt, pc, alignedValue)
// Update the current text symbol alignment value.
if int32(alignedValue) > cursym.Func().Align {
cursym.Func().Align = int32(alignedValue)
@ -1150,7 +1151,7 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
switch p.As {
case obj.APCALIGN:
alignedValue := p.From.Offset
m = pcAlignPadLength(pc, alignedValue, ctxt)
m = pcAlignPadLength(ctxt, pc, alignedValue)
break
case obj.ANOP, obj.AFUNCDATA, obj.APCDATA:
continue
@ -1183,7 +1184,7 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
}
if p.As == obj.APCALIGN {
alignedValue := p.From.Offset
v := pcAlignPadLength(p.Pc, alignedValue, c.ctxt)
v := pcAlignPadLength(c.ctxt, p.Pc, alignedValue)
for i = 0; i < int(v/4); i++ {
// emit ANOOP instruction by the padding size
c.ctxt.Arch.ByteOrder.PutUint32(bp, OP_NOOP)