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x86: Emit LOCK prefix after DATA16

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Summary: x86 allows either ordering for the LOCK and DATA16 prefixes, but using GCC+GAS leads to different code generation than using LLVM. This change matches the order that GAS emits the x86 prefixes when a semicolon isn't used in inline assembly (see tc-i386.c comment before define LOCK_PREFIX), and helps simplify tooling that operates on the instruction's byte sequence (such as NaCl's validator). This change shouldn't have any performance impact.

Test Plan: ninja check

Reviewers: craig.topper, jvoung

Subscribers: jfb, llvm-commits

Differential Revision: http://reviews.llvm.org/D6630

llvm-svn: 224283
This commit is contained in:
JF Bastien 2014-12-15 22:34:58 +00:00
parent a6e921963f
commit 27a63b4d77
2 changed files with 18 additions and 16 deletions
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10
lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
View File

@ -590,6 +590,8 @@ void X86MCCodeEmitter::EmitVEXOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
int MemOperand, const MCInst &MI,
const MCInstrDesc &Desc,
raw_ostream &OS) const {
assert(!(TSFlags & X86II::LOCK) && "Can't have LOCK VEX.");
uint64_t Encoding = TSFlags & X86II::EncodingMask;
bool HasEVEX_K = TSFlags & X86II::EVEX_K;
bool HasVEX_4V = TSFlags & X86II::VEX_4V;
@ -1109,6 +1111,10 @@ void X86MCCodeEmitter::EmitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
: X86II::OpSize16))
EmitByte(0x66, CurByte, OS);
// Emit the LOCK opcode prefix.
if (TSFlags & X86II::LOCK)
EmitByte(0xF0, CurByte, OS);
switch (TSFlags & X86II::OpPrefixMask) {
case X86II::PD: // 66
EmitByte(0x66, CurByte, OS);
@ -1182,10 +1188,6 @@ EncodeInstruction(const MCInst &MI, raw_ostream &OS,
int MemoryOperand = X86II::getMemoryOperandNo(TSFlags, Opcode);
if (MemoryOperand != -1) MemoryOperand += CurOp;
// Emit the lock opcode prefix as needed.
if (TSFlags & X86II::LOCK)
EmitByte(0xF0, CurByte, OS);
// Emit segment override opcode prefix as needed.
if (MemoryOperand >= 0)
EmitSegmentOverridePrefix(CurByte, MemoryOperand+X86::AddrSegmentReg,

24
test/CodeGen/X86/atomic16.ll
View File

@ -15,17 +15,17 @@ entry:
; X32: incw
%t2 = atomicrmw add i16* @sc16, i16 3 acquire
; X64: lock
; X64: addw $3, {{.*}} # encoding: [0xf0,0x66
; X64: addw $3, {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: addw $3
%t3 = atomicrmw add i16* @sc16, i16 5 acquire
; X64: lock
; X64: xaddw {{.*}} # encoding: [0xf0,0x66
; X64: xaddw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: xaddw
%t4 = atomicrmw add i16* @sc16, i16 %t3 acquire
; X64: lock
; X64: addw {{.*}} # encoding: [0xf0,0x66
; X64: addw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: addw
ret void
@ -43,17 +43,17 @@ define void @atomic_fetch_sub16() nounwind {
; X32: decw
%t2 = atomicrmw sub i16* @sc16, i16 3 acquire
; X64: lock
; X64: subw $3, {{.*}} # encoding: [0xf0,0x66
; X64: subw $3, {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: subw $3
%t3 = atomicrmw sub i16* @sc16, i16 5 acquire
; X64: lock
; X64: xaddw {{.*}} # encoding: [0xf0,0x66
; X64: xaddw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: xaddw
%t4 = atomicrmw sub i16* @sc16, i16 %t3 acquire
; X64: lock
; X64: subw {{.*}} # encoding: [0xf0,0x66
; X64: subw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: subw
ret void
@ -66,7 +66,7 @@ define void @atomic_fetch_and16() nounwind {
; X32-LABEL: atomic_fetch_and16
%t1 = atomicrmw and i16* @sc16, i16 3 acquire
; X64: lock
; X64: andw $3, {{.*}} # encoding: [0xf0,0x66
; X64: andw $3, {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: andw $3
%t2 = atomicrmw and i16* @sc16, i16 5 acquire
@ -78,7 +78,7 @@ define void @atomic_fetch_and16() nounwind {
; X32: cmpxchgw
%t3 = atomicrmw and i16* @sc16, i16 %t2 acquire
; X64: lock
; X64: andw {{.*}} # encoding: [0xf0,0x66
; X64: andw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: andw
ret void
@ -91,7 +91,7 @@ define void @atomic_fetch_or16() nounwind {
; X32-LABEL: atomic_fetch_or16
%t1 = atomicrmw or i16* @sc16, i16 3 acquire
; X64: lock
; X64: orw $3, {{.*}} # encoding: [0xf0,0x66
; X64: orw $3, {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: orw $3
%t2 = atomicrmw or i16* @sc16, i16 5 acquire
@ -103,7 +103,7 @@ define void @atomic_fetch_or16() nounwind {
; X32: cmpxchgw
%t3 = atomicrmw or i16* @sc16, i16 %t2 acquire
; X64: lock
; X64: orw {{.*}} # encoding: [0xf0,0x66
; X64: orw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: orw
ret void
@ -116,7 +116,7 @@ define void @atomic_fetch_xor16() nounwind {
; X32-LABEL: atomic_fetch_xor16
%t1 = atomicrmw xor i16* @sc16, i16 3 acquire
; X64: lock
; X64: xorw $3, {{.*}} # encoding: [0xf0,0x66
; X64: xorw $3, {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: xorw $3
%t2 = atomicrmw xor i16* @sc16, i16 5 acquire
@ -128,7 +128,7 @@ define void @atomic_fetch_xor16() nounwind {
; X32: cmpxchgw
%t3 = atomicrmw xor i16* @sc16, i16 %t2 acquire
; X64: lock
; X64: xorw {{.*}} # encoding: [0xf0,0x66
; X64: xorw {{.*}} # encoding: [0x66,0xf0
; X32: lock
; X32: xorw
ret void