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Refactor X86TargetInfo::relaxTlsIeToLe. 

`Inst` and `Op` variables are removed since they are not always
point to an instruction nor an operand. For 5-byte MOV instruction,
Op points to an instruction, which is confusing.

llvm-svn: 273246
This commit is contained in:
Rui Ueyama 2016-06-21 05:44:14 +00:00
parent 03c1415b8f
commit b319ae2cf1
1 changed files with 23 additions and 23 deletions
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46
lld/ELF/Target.cpp
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@ -475,34 +475,34 @@ void X86TargetInfo::relaxTlsIeToLe(uint8_t *Loc, uint32_t Type,
// be used with MOVL or ADDL instructions.
// @indntpoff is similar to @gotntpoff, but for use in
// position dependent code.
uint8_t *Inst = Loc - 2;
uint8_t *Op = Loc - 1;
uint8_t Reg = (Loc[-1] >> 3) & 7;
bool IsMov = *Inst == 0x8b;
if (Type == R_386_TLS_IE) {
// For R_386_TLS_IE relocation we perform the next transformations:
// MOVL foo@INDNTPOFF,%EAX is transformed to MOVL $foo,%EAX
// MOVL foo@INDNTPOFF,%REG is transformed to MOVL $foo,%REG
// ADDL foo@INDNTPOFF,%REG is transformed to ADDL $foo,%REG
// First one is special because when EAX is used the sequence is 5 bytes
// long, otherwise it is 6 bytes.
if (*Op == 0xa1) {
*Op = 0xb8;
if (Loc[-1] == 0xa1) {
// "movl foo@indntpoff,%eax" -> "movl $foo,%eax"
// This case is different from the generic case below because
// this is a 5 byte instruction while below is 6 bytes.
Loc[-1] = 0xb8;
} else if (Loc[-2] == 0x8b) {
// "movl foo@indntpoff,%reg" -> "movl $foo,%reg"
Loc[-2] = 0xc7;
Loc[-1] = 0xc0 | Reg;
} else {
*Inst = IsMov ? 0xc7 : 0x81;
*Op = 0xc0 | ((*Op >> 3) & 7);
// "addl foo@indntpoff,%reg" -> "addl $foo,%reg"
Loc[-2] = 0x81;
Loc[-1] = 0xc0 | Reg;
}
} else {
// R_386_TLS_GOTIE relocation can be optimized to
// R_386_TLS_LE so that it does not use GOT.
// "MOVL foo@GOTTPOFF(%RIP), %REG" is transformed to "MOVL $foo, %REG".
// "ADDL foo@GOTNTPOFF(%RIP), %REG" is transformed to "LEAL foo(%REG), %REG"
// Note: gold converts to ADDL instead of LEAL.
*Inst = IsMov ? 0xc7 : 0x8d;
if (IsMov)
*Op = 0xc0 | ((*Op >> 3) & 7);
else
*Op = 0x80 | Reg | (Reg << 3);
assert(Type == R_386_TLS_GOTIE);
if (Loc[-2] == 0x8b) {
// "movl foo@gottpoff(%rip),%reg" -> "movl $foo,%reg"
Loc[-2] = 0xc7;
Loc[-1] = 0xc0 | Reg;
} else {
// "addl foo@gotntpoff(%rip),%reg" -> "leal foo(%reg),%reg"
Loc[-2] = 0x8d;
Loc[-1] = 0x80 | (Reg << 3) | Reg;
}
}
relocateOne(Loc, R_386_TLS_LE, Val);
}