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6l: Relocate CMOV* instructions
The linker avoids a GOT indirection by turning a MOV into a LEA, but with x86-64 GCC has started emitting CMOV* instructions which break the existing logic. This will generate errors such as: unexpected GOT reloc for non-dynamic symbol luaO_nilobject_ The CMOV* instructions may be emitted with normal code like: if (o >= L->top) return cast(TValue *, luaO_nilobject); else return o; Which gets compiled into (relocation offset at 1b): 13: 48 3b 47 10 cmp 0x10(%rdi),%rax 17: 48 0f 43 05 00 00 00 cmovae 0x0(%rip),%rax 1e: 00 This change will allow the indirection through the GOT to avoid the problem in those cases. R=golang-dev, rsc CC=golang-dev https://golang.org/cl/4071044
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@ -206,15 +206,15 @@ adddynrel(Sym *s, Reloc *r)
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case 256 + R_X86_64_GOTPCREL:
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if(targ->dynimpname == nil || targ->dynexport) {
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// have symbol
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// turn MOVQ of GOT entry into LEAQ of symbol itself
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if(r->off < 2 || s->p[r->off-2] != 0x8b) {
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diag("unexpected GOT_LOAD reloc for non-dynamic symbol %s", targ->name);
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if(r->off >= 2 && s->p[r->off-2] == 0x8b) {
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// turn MOVQ of GOT entry into LEAQ of symbol itself
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s->p[r->off-2] = 0x8d;
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r->type = D_PCREL;
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r->add += 4;
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return;
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}
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s->p[r->off-2] = 0x8d;
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r->type = D_PCREL;
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r->add += 4;
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return;
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// unknown instruction (CMOV* maybe), use GOT
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targ->dynimpname = targ->name;
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}
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addgotsym(targ);
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r->type = D_PCREL;
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