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cmd/internal/obj/x86: fix duffcopy/duffzero for GOEXPERIMENT=framepointer

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Change-Id: I99aee6dff97a4abcaf5a9cddb505ba90b65667ea
Reviewed-on: https://go-review.googlesource.com/7728
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Russ Cox 2015-03-16 21:19:08 -04:00
parent f63678ae91
commit 08af4c3a79
1 changed files with 40 additions and 4 deletions
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44
src/cmd/internal/obj/x86/asm6.go
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@ -164,6 +164,7 @@ const (
Zbr
Zcall
Zcallcon
Zcallduff
Zcallind
Zcallindreg
Zib_
@ -528,7 +529,7 @@ var ycall = []ytab{
}
var yduff = []ytab{
{Ynone, Ynone, Yi32, Zcall, 1},
{Ynone, Ynone, Yi32, Zcallduff, 1},
}
var yjmp = []ytab{
@ -2913,6 +2914,16 @@ func mediaop(ctxt *obj.Link, o *Optab, op int, osize int, z int) int {
return z
}
var bpduff1 = []byte{
0x48, 0x89, 0x6c, 0x24, 0xf0, // MOVQ BP, -16(SP)
0x48, 0x8d, 0x6c, 0x24, 0xf0, // LEAQ -16(SP), BP
}
var bpduff2 = []byte{
0x90,
0x48, 0x8b, 0x6d, 0x00, // MOVQ 0(BP), BP
}
func doasm(ctxt *obj.Link, p *obj.Prog) {
ctxt.Curp = p // TODO
@ -3436,12 +3447,23 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
r.Sym = p.To.Sym
put4(ctxt, 0)
case Zcall:
case Zcall, Zcallduff:
if p.To.Sym == nil {
ctxt.Diag("call without target")
log.Fatalf("bad code")
}
if obj.Framepointer_enabled != 0 && yt.zcase == Zcallduff && p.Mode == 64 {
// Maintain BP around call, since duffcopy/duffzero can't do it
// (the call jumps into the middle of the function).
// This makes it possible to see call sites for duffcopy/duffzero in
// BP-based profiling tools like Linux perf (which is the
// whole point of obj.Framepointer_enabled).
// MOVQ BP, -16(SP)
// LEAQ -16(SP), BP
copy(ctxt.Andptr, bpduff1)
ctxt.Andptr = ctxt.Andptr[len(bpduff1):]
}
ctxt.Andptr[0] = byte(op)
ctxt.Andptr = ctxt.Andptr[1:]
r = obj.Addrel(ctxt.Cursym)
@ -3452,7 +3474,14 @@ func doasm(ctxt *obj.Link, p *obj.Prog) {
r.Siz = 4
put4(ctxt, 0)
// TODO: jump across functions needs reloc
if obj.Framepointer_enabled != 0 && yt.zcase == Zcallduff && p.Mode == 64 {
// Pop BP pushed above.
// MOVQ 0(BP), BP
copy(ctxt.Andptr, bpduff2)
ctxt.Andptr = ctxt.Andptr[len(bpduff2):]
}
// TODO: jump across functions needs reloc
case Zbr,
Zjmp,
Zloop:
@ -4339,7 +4368,14 @@ func asmins(ctxt *obj.Link, p *obj.Prog) {
if ctxt.Rexflag != 0 {
r.Off++
}
if r.Type == obj.R_PCREL || r.Type == obj.R_CALL {
if r.Type == obj.R_PCREL {
// PC-relative addressing is relative to the end of the instruction,
// but the relocations applied by the linker are relative to the end
// of the relocation. Because immediate instruction
// arguments can follow the PC-relative memory reference in the
// instruction encoding, the two may not coincide. In this case,
// adjust addend so that linker can keep relocating relative to the
// end of the relocation.
r.Add -= p.Pc + int64(n) - (int64(r.Off) + int64(r.Siz))
}
}