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cmd/internal/obj/arm: optimize MOVW $-off(R), R

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When offset < 0 and -offset fits in instruction, generate SUB
instruction, instead of ADD with constant from the pool.

Fixes #13280.

Change-Id: I57d97fe9300fe1f6554365e2262393ef50acbdd3
Reviewed-on: https://go-review.googlesource.com/30014
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Cherry Zhang 2016-09-29 09:22:01 -04:00
parent 26531b3846
commit fedb0b3018
1 changed files with 12 additions and 6 deletions
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18
src/cmd/internal/obj/arm/asm5.go
View file

@ -1155,8 +1155,10 @@ func aclass(ctxt *obj.Link, a *obj.Addr) int {
}
func aconsize(ctxt *obj.Link) int {
t := int(immrot(uint32(ctxt.Instoffset)))
if t != 0 {
if t := int(immrot(uint32(ctxt.Instoffset))); t != 0 {
return C_RACON
}
if t := int(immrot(uint32(-ctxt.Instoffset))); t != 0 {
return C_RACON
}
return C_LACON
@ -1537,11 +1539,15 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
case 3: /* add R<<[IR],[R],R */
o1 = mov(ctxt, p)
case 4: /* add $I,[R],R */
case 4: /* MOVW $off(R), R -> add $off,[R],R */
aclass(ctxt, &p.From)
o1 = oprrr(ctxt, AADD, int(p.Scond))
o1 |= uint32(immrot(uint32(ctxt.Instoffset)))
if ctxt.Instoffset < 0 {
o1 = oprrr(ctxt, ASUB, int(p.Scond))
o1 |= uint32(immrot(uint32(-ctxt.Instoffset)))
} else {
o1 = oprrr(ctxt, AADD, int(p.Scond))
o1 |= uint32(immrot(uint32(ctxt.Instoffset)))
}
r := int(p.From.Reg)
if r == 0 {
r = int(o.param)