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cmd/internal/obj/x86, cmd/link: enable access to global data via GOT when -dynlink on 386
Change-Id: I97504a11291ee60e656efb7704e37387e864d74f Reviewed-on: https://go-review.googlesource.com/16385 Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Michael Hudson-Doyle
parent
cb0393866a
commit
342f17eaf7
3 changed files with 120 additions and 29 deletions
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@ -319,12 +319,25 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
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// Rewrite p, if necessary, to access global data via the global offset table.
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func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
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var add, lea, mov, reg int16
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if p.Mode == 64 {
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add = AADDQ
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lea = ALEAQ
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mov = AMOVQ
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reg = REG_R15
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} else {
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add = AADDL
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lea = ALEAL
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mov = AMOVL
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reg = REG_CX
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}
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if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
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// ADUFFxxx $offset
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// becomes
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// MOVQ runtime.duffxxx@GOT, R15
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// ADDQ $offset, R15
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// CALL R15
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// $MOV runtime.duffxxx@GOT, $reg
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// $ADD $offset, $reg
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// CALL $reg
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var sym *obj.LSym
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if p.As == obj.ADUFFZERO {
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sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
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@ -332,60 +345,78 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
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sym = obj.Linklookup(ctxt, "runtime.duffcopy", 0)
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}
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offset := p.To.Offset
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p.As = AMOVQ
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p.As = mov
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p.From.Type = obj.TYPE_MEM
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p.From.Name = obj.NAME_GOTREF
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p.From.Sym = sym
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p.To.Type = obj.TYPE_REG
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p.To.Reg = REG_R15
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p.To.Reg = reg
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p.To.Offset = 0
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p.To.Sym = nil
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p1 := obj.Appendp(ctxt, p)
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p1.As = AADDQ
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p1.As = add
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p1.From.Type = obj.TYPE_CONST
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p1.From.Offset = offset
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p1.To.Type = obj.TYPE_REG
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p1.To.Reg = REG_R15
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p1.To.Reg = reg
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p2 := obj.Appendp(ctxt, p1)
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p2.As = obj.ACALL
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p2.To.Type = obj.TYPE_REG
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p2.To.Reg = REG_R15
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p2.To.Reg = reg
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}
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// We only care about global data: NAME_EXTERN means a global
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// symbol in the Go sense, and p.Sym.Local is true for a few
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// internally defined symbols.
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if p.As == ALEAQ && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
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// LEAQ sym, Rx becomes MOVQ $sym, Rx which will be rewritten below
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p.As = AMOVQ
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if p.As == lea && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
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// $LEA sym, Rx becomes $MOV $sym, Rx which will be rewritten below
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p.As = mov
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p.From.Type = obj.TYPE_ADDR
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}
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if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
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// MOVQ $sym, Rx becomes MOVQ sym@GOT, Rx
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// MOVQ $sym+<off>, Rx becomes MOVQ sym@GOT, Rx; ADDQ <off>, Rx
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if p.As != AMOVQ {
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ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
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}
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if p.To.Type != obj.TYPE_REG {
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ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
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// $MOV $sym, Rx becomes $MOV sym@GOT, Rx
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// $MOV $sym+<off>, Rx becomes $MOV sym@GOT, Rx; $ADD <off>, Rx
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// On 386 only, more complicated things like PUSHL $sym become $MOV sym@GOT, CX; PUSHL CX
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cmplxdest := false
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pAs := p.As
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var dest obj.Addr
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if p.To.Type != obj.TYPE_REG || pAs != mov {
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if p.Mode == 64 {
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ctxt.Diag("do not know how to handle LEA-type insn to non-register in %v with -dynlink", p)
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}
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cmplxdest = true
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dest = p.To
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p.As = mov
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p.To.Type = obj.TYPE_REG
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p.To.Reg = REG_CX
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p.To.Sym = nil
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p.To.Name = obj.NAME_NONE
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}
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p.From.Type = obj.TYPE_MEM
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p.From.Name = obj.NAME_GOTREF
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q := p
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if p.From.Offset != 0 {
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q := obj.Appendp(ctxt, p)
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q.As = AADDQ
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q = obj.Appendp(ctxt, p)
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q.As = add
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q.From.Type = obj.TYPE_CONST
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q.From.Offset = p.From.Offset
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q.To = p.To
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p.From.Offset = 0
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}
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if cmplxdest {
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q = obj.Appendp(ctxt, q)
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q.As = pAs
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q.To = dest
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_CX
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}
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}
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if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
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ctxt.Diag("don't know how to handle %v with -dynlink", p)
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}
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var source *obj.Addr
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// MOVx sym, Ry becomes MOVW sym@GOT, R15; MOVx (R15), Ry
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// MOVx Ry, sym becomes MOVW sym@GOT, R15; MOVx Ry, (R15)
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// MOVx sym, Ry becomes $MOV sym@GOT, R15; MOVx (R15), Ry
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// MOVx Ry, sym becomes $MOV sym@GOT, R15; MOVx Ry, (R15)
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// An addition may be inserted between the two MOVs if there is an offset.
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if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
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if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
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@ -397,7 +428,41 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
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} else {
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return
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}
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if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
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if p.As == obj.ACALL {
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// When dynlinking on 386, almost any call might end up being a call
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// to a PLT, so make sure the GOT pointer is loaded into BX.
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// RegTo2 is set on the replacement call insn to stop it being
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// processed when it is in turn passed to progedit.
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if p.Mode == 64 || (p.To.Sym != nil && p.To.Sym.Local) || p.RegTo2 != 0 {
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return
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}
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p1 := obj.Appendp(ctxt, p)
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p2 := obj.Appendp(ctxt, p1)
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p1.As = ALEAL
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p1.From.Type = obj.TYPE_MEM
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p1.From.Name = obj.NAME_STATIC
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p1.From.Sym = obj.Linklookup(ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
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p1.To.Type = obj.TYPE_REG
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p1.To.Reg = REG_BX
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p2.As = p.As
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p2.Scond = p.Scond
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p2.From = p.From
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p2.From3 = p.From3
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p2.Reg = p.Reg
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p2.To = p.To
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// p.To.Type was set to TYPE_BRANCH above, but that makes checkaddr
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// in ../pass.go complain, so set it back to TYPE_MEM here, until p2
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// itself gets passed to progedit.
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p2.To.Type = obj.TYPE_MEM
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p2.RegTo2 = 1
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obj.Nopout(p)
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return
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}
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if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ARET || p.As == obj.AJMP {
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return
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}
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if source.Type != obj.TYPE_MEM {
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@ -406,22 +471,22 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
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p1 := obj.Appendp(ctxt, p)
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p2 := obj.Appendp(ctxt, p1)
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p1.As = AMOVQ
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p1.As = mov
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p1.From.Type = obj.TYPE_MEM
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p1.From.Sym = source.Sym
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p1.From.Name = obj.NAME_GOTREF
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p1.To.Type = obj.TYPE_REG
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p1.To.Reg = REG_R15
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p1.To.Reg = reg
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p2.As = p.As
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p2.From = p.From
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p2.To = p.To
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if p.From.Name == obj.NAME_EXTERN {
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p2.From.Reg = REG_R15
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p2.From.Reg = reg
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p2.From.Name = obj.NAME_NONE
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p2.From.Sym = nil
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} else if p.To.Name == obj.NAME_EXTERN {
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p2.To.Reg = REG_R15
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p2.To.Reg = reg
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p2.To.Name = obj.NAME_NONE
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p2.To.Sym = nil
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} else {
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