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cmd/6g: let the compiler use R15 when it is not needed for GOT indirection 

Thanks to Russ for the hints.

Change-Id: Ie35a71d432b9d68bd30c7a364b4dce1bd3db806e
Reviewed-on: https://go-review.googlesource.com/9102
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2015-04-17 08:36:11 +02:00 committed by Ian Lance Taylor
parent 88c08b06b9
commit 8a3132dd5e
2 changed files with 19 additions and 9 deletions
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12
src/cmd/6g/prog.go
View File

@ -293,4 +293,16 @@ func proginfo(p *obj.Prog) {
if p.To.Index != x86.REG_NONE {
info.Regindex |= RtoB(int(p.To.Index))
}
if gc.Ctxt.Flag_dynlink {
// When -dynlink is passed, many operations on external names (and
// also calling duffzero/duffcopy) use R15 as a scratch register.
if p.As == x86.ALEAQ || info.Flags == gc.Pseudo || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
return
}
if p.As == obj.ADUFFZERO || p.As == obj.ADUFFCOPY || p.From.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_EXTERN {
info.Reguse |= R15
info.Regset |= R15
return
}
}
}

16
src/cmd/6g/reg.go
View File

@ -102,12 +102,13 @@ func doregbits(r int) uint64 {
// For ProgInfo.
const (
AX = 1 << (x86.REG_AX - x86.REG_AX)
BX = 1 << (x86.REG_BX - x86.REG_AX)
CX = 1 << (x86.REG_CX - x86.REG_AX)
DX = 1 << (x86.REG_DX - x86.REG_AX)
DI = 1 << (x86.REG_DI - x86.REG_AX)
SI = 1 << (x86.REG_SI - x86.REG_AX)
AX = 1 << (x86.REG_AX - x86.REG_AX)
BX = 1 << (x86.REG_BX - x86.REG_AX)
CX = 1 << (x86.REG_CX - x86.REG_AX)
DX = 1 << (x86.REG_DX - x86.REG_AX)
DI = 1 << (x86.REG_DI - x86.REG_AX)
SI = 1 << (x86.REG_SI - x86.REG_AX)
R15 = 1 << (x86.REG_R15 - x86.REG_AX)
)
func RtoB(r int) uint64 {
@ -125,9 +126,6 @@ func BtoR(b uint64) int {
// BP is part of the calling convention if framepointer_enabled.
b &^= (1 << (x86.REG_BP - x86.REG_AX))
}
if gc.Ctxt.Flag_dynlink {
b &^= (1 << (x86.REG_R15 - x86.REG_AX))
}
if b == 0 {
return 0
}