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Inline a trivial function and update comment. NFC. 

llvm-svn: 353200
This commit is contained in:
Rui Ueyama 2019-02-05 19:19:45 +00:00
parent 76f787424d
commit 3fdb07258b
1 changed files with 7 additions and 9 deletions
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16
lld/ELF/Arch/X86.cpp
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@ -66,8 +66,6 @@ X86::X86() {
DefaultImageBase = 0x400000; DefaultImageBase = 0x400000;
} }
static bool hasBaseReg(uint8_t ModRM) { return (ModRM & 0xc7) != 0x5; }
RelExpr X86::getRelExpr(RelType Type, const Symbol &S, RelExpr X86::getRelExpr(RelType Type, const Symbol &S,
const uint8_t *Loc) const { const uint8_t *Loc) const {
switch (Type) { switch (Type) {
@ -107,14 +105,14 @@ RelExpr X86::getRelExpr(RelType Type, const Symbol &S,
// load an GOT address to a register, which is usually %ebx. // load an GOT address to a register, which is usually %ebx.
// //
// So, there are two ways to refer to symbol foo's GOT entry: foo@GOT or // So, there are two ways to refer to symbol foo's GOT entry: foo@GOT or
// foo@GOT(%reg). // foo@GOT(%ebx).
// //
// foo@GOT is not usable in PIC. If we are creating a PIC output and if we // foo@GOT is not usable in PIC. If we are creating a PIC output and if we
// find such relocation, we should report an error. foo@GOT is resolved to // find such relocation, we should report an error. foo@GOT is resolved to
// an *absolute* address of foo's GOT entry, because both GOT address and // an *absolute* address of foo's GOT entry, because both GOT address and
// foo's offset are known. In other words, it's G + A. // foo's offset are known. In other words, it's G + A.
// //
// foo@GOT(%reg) needs to be resolved to a *relative* offset from a GOT to // foo@GOT(%ebx) needs to be resolved to a *relative* offset from a GOT to
// foo's GOT entry in the table, because GOT address is not known but foo's // foo's GOT entry in the table, because GOT address is not known but foo's
// offset in the table is known. It's G + A - GOT. // offset in the table is known. It's G + A - GOT.
// //
@ -122,12 +120,12 @@ RelExpr X86::getRelExpr(RelType Type, const Symbol &S,
// different use cases. In order to distinguish them, we have to read a // different use cases. In order to distinguish them, we have to read a
// machine instruction. // machine instruction.
// //
// The following code implements it. We assume that Loc[0] is the first // The following code implements it. We assume that Loc[0] is the first byte
// byte of a displacement or an immediate field of a valid machine // of a displacement or an immediate field of a valid machine
// instruction. That means a ModRM byte is at Loc[-1]. By taking a look at // instruction. That means a ModRM byte is at Loc[-1]. By taking a look at
// the byte, we can determine whether the instruction is register-relative // the byte, we can determine whether the instruction uses the operand as an
// (i.e. it was generated for foo@GOT(%reg)) or absolute (i.e. foo@GOT). // absolute address (R_GOT) or a register-relative address (R_GOT_FROM_END).
return hasBaseReg(Loc[-1]) ? R_GOT_FROM_END : R_GOT; return (Loc[-1] & 0xc7) == 0x5 ? R_GOT : R_GOT_FROM_END;
case R_386_TLS_GOTIE: case R_386_TLS_GOTIE:
return R_GOT_FROM_END; return R_GOT_FROM_END;
case R_386_GOTOFF: case R_386_GOTOFF: