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cmd/internal/obj/x86: factor rewriting to use GOT into separate function
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I was prodded into doing this in review comments for the ARM version, and it's
going to make shared libs for 386 easier.

Change-Id: Id12de801b1425b8c6b5736fe91b418fc123a4e40
Reviewed-on: https://go-review.googlesource.com/17012
Reviewed-by: David Crawshaw <crawshaw@golang.org>
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@mwhudson
mwhudson committed Nov 18, 2015
1 parent 6bf794a commit 3c85e1b
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Showing 3 changed files with 93 additions and 76 deletions.
5 changes: 4 additions & 1 deletion src/cmd/internal/obj/x86/asm6.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2090,8 +2090,11 @@ func oclass(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) int {

case obj.TYPE_ADDR:
switch a.Name {
case obj.NAME_GOTREF:
ctxt.Diag("unexpected TYPE_ADDR with NAME_GOTREF")
return Yxxx

case obj.NAME_EXTERN,
obj.NAME_GOTREF,
obj.NAME_STATIC:
if a.Sym != nil && isextern(a.Sym) || p.Mode == 32 {
return Yi32
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154 changes: 84 additions & 70 deletions src/cmd/internal/obj/x86/obj6.go
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Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,19 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
}
}

if ctxt.Flag_dynlink && (p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO) {
if ctxt.Flag_dynlink {
rewriteToUseGot(ctxt, p)
}
}

// Rewrite p, if necessary, to access global data via the global offset table.
func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
// ADUFFxxx $offset
// becomes
// MOVQ runtime.duffxxx@GOT, R15
// ADDQ $offset, R15
// CALL R15
var sym *obj.LSym
if p.As == obj.ADUFFZERO {
sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
Expand Down Expand Up @@ -336,80 +348,82 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
p2.To.Reg = REG_R15
}

if ctxt.Flag_dynlink {
if p.As == ALEAQ && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
p.As = AMOVQ
p.From.Type = obj.TYPE_ADDR
}
if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
if p.As != AMOVQ {
ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
}
if p.To.Type != obj.TYPE_REG {
ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
}
p.From.Type = obj.TYPE_MEM
p.From.Name = obj.NAME_GOTREF
if p.From.Offset != 0 {
q := obj.Appendp(ctxt, p)
q.As = AADDQ
q.From.Type = obj.TYPE_CONST
q.From.Offset = p.From.Offset
q.To = p.To
p.From.Offset = 0
}
}
if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
ctxt.Diag("don't know how to handle %v with -dynlink", p)
}
var source *obj.Addr
if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
}
source = &p.From
} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
source = &p.To
} else {
return
// We only care about global data: NAME_EXTERN means a global
// symbol in the Go sense, and p.Sym.Local is true for a few
// internally defined symbols.
if p.As == ALEAQ && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
// LEAQ sym, Rx becomes MOVQ $sym, Rx which will be rewritten below
p.As = AMOVQ
p.From.Type = obj.TYPE_ADDR
}
if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
// MOVQ $sym, Rx becomes MOVQ sym@GOT, Rx
// MOVQ $sym+<off>, Rx becomes MOVQ sym@GOT, Rx; ADDQ <off>, Rx
if p.As != AMOVQ {
ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
}
if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
return
if p.To.Type != obj.TYPE_REG {
ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
}
if source.Type != obj.TYPE_MEM {
ctxt.Diag("don't know how to handle %v with -dynlink", p)
p.From.Type = obj.TYPE_MEM
p.From.Name = obj.NAME_GOTREF
if p.From.Offset != 0 {
q := obj.Appendp(ctxt, p)
q.As = AADDQ
q.From.Type = obj.TYPE_CONST
q.From.Offset = p.From.Offset
q.To = p.To
p.From.Offset = 0
}
p1 := obj.Appendp(ctxt, p)
p2 := obj.Appendp(ctxt, p1)

p1.As = AMOVQ
p1.From.Type = obj.TYPE_MEM
p1.From.Sym = source.Sym
p1.From.Name = obj.NAME_GOTREF
p1.To.Type = obj.TYPE_REG
p1.To.Reg = REG_R15

p2.As = p.As
p2.From = p.From
p2.To = p.To
if p.From.Name == obj.NAME_EXTERN {
p2.From.Reg = REG_R15
p2.From.Name = obj.NAME_NONE
p2.From.Sym = nil
} else if p.To.Name == obj.NAME_EXTERN {
p2.To.Reg = REG_R15
p2.To.Name = obj.NAME_NONE
p2.To.Sym = nil
} else {
return
}
if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
ctxt.Diag("don't know how to handle %v with -dynlink", p)
}
var source *obj.Addr
// MOVx sym, Ry becomes MOVW sym@GOT, R15; MOVx (R15), Ry
// MOVx Ry, sym becomes MOVW sym@GOT, R15; MOVx Ry, (R15)
// An addition may be inserted between the two MOVs if there is an offset.
if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
}
l := p.Link
l2 := p2.Link
*p = *p1
*p1 = *p2
p.Link = l
p1.Link = l2
source = &p.From
} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
source = &p.To
} else {
return
}
if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
return
}
if source.Type != obj.TYPE_MEM {
ctxt.Diag("don't know how to handle %v with -dynlink", p)
}
p1 := obj.Appendp(ctxt, p)
p2 := obj.Appendp(ctxt, p1)

p1.As = AMOVQ
p1.From.Type = obj.TYPE_MEM
p1.From.Sym = source.Sym
p1.From.Name = obj.NAME_GOTREF
p1.To.Type = obj.TYPE_REG
p1.To.Reg = REG_R15

p2.As = p.As
p2.From = p.From
p2.To = p.To
if p.From.Name == obj.NAME_EXTERN {
p2.From.Reg = REG_R15
p2.From.Name = obj.NAME_NONE
p2.From.Sym = nil
} else if p.To.Name == obj.NAME_EXTERN {
p2.To.Reg = REG_R15
p2.To.Name = obj.NAME_NONE
p2.To.Sym = nil
} else {
return
}
obj.Nopout(p)
}

func nacladdr(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
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10 changes: 5 additions & 5 deletions src/cmd/internal/obj/x86/obj6_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,13 +24,13 @@ LEAQ name+10(SB), AX -> MOVQ name@GOT(SB), AX; ADDQ $10, AX
MOVQ $name(SB), AX -> MOVQ name@GOT(SB), AX
MOVQ $name+10(SB), AX -> MOVQ name@GOT(SB), AX; ADDQ $10, AX
MOVQ name(SB), AX -> MOVQ name@GOT(SB), R15; MOVQ (R15), AX
MOVQ name+10(SB), AX -> MOVQ name@GOT(SB), R15; MOVQ 10(R15), AX
MOVQ name(SB), AX -> NOP; MOVQ name@GOT(SB), R15; MOVQ (R15), AX
MOVQ name+10(SB), AX -> NOP; MOVQ name@GOT(SB), R15; MOVQ 10(R15), AX
CMPQ name(SB), $0 -> MOVQ name@GOT(SB), R15; CMPQ (R15), $0
CMPQ name(SB), $0 -> NOP; MOVQ name@GOT(SB), R15; CMPQ (R15), $0
MOVQ $1, name(SB) -> MOVQ name@GOT(SB), R15; MOVQ $1, (R15)
MOVQ $1, name+10(SB) -> MOVQ name@GOT(SB), R15; MOVQ $1, 10(R15)
MOVQ $1, name(SB) -> NOP; MOVQ name@GOT(SB), R15; MOVQ $1, (R15)
MOVQ $1, name+10(SB) -> NOP; MOVQ name@GOT(SB), R15; MOVQ $1, 10(R15)
`

type ParsedTestData struct {
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