The MONITOR and MWAIT instructions have insufficient information for
decoding. Essentially, they both map to the same column in the "opcode
extensions for one- and two-byte opcodes" table in the x86 manual. The RawFrm
complicates decoding this.
Instead, use opcode 0x01, prefix 0x01, and form MRM1r. Then have the code
emitter special case these, a la [SML]FENCE.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72556 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86CodeEmitter.cpp b/lib/Target/X86/X86CodeEmitter.cpp
index 63bf18d..efd64e0 100644
--- a/lib/Target/X86/X86CodeEmitter.cpp
+++ b/lib/Target/X86/X86CodeEmitter.cpp
@@ -671,13 +671,26 @@
case X86II::MRM6r: case X86II::MRM7r: {
MCE.emitByte(BaseOpcode);
- // Special handling of lfence and mfence.
+ // Special handling of lfence, mfence, monitor, and mwait.
if (Desc->getOpcode() == X86::LFENCE ||
- Desc->getOpcode() == X86::MFENCE)
+ Desc->getOpcode() == X86::MFENCE ||
+ Desc->getOpcode() == X86::MONITOR ||
+ Desc->getOpcode() == X86::MWAIT) {
emitRegModRMByte((Desc->TSFlags & X86II::FormMask)-X86II::MRM0r);
- else
+
+ switch (Desc->getOpcode()) {
+ default: break;
+ case X86::MONITOR:
+ MCE.emitByte(0xC8);
+ break;
+ case X86::MWAIT:
+ MCE.emitByte(0xC9);
+ break;
+ }
+ } else {
emitRegModRMByte(MI.getOperand(CurOp++).getReg(),
(Desc->TSFlags & X86II::FormMask)-X86II::MRM0r);
+ }
if (CurOp != NumOps) {
const MachineOperand &MO1 = MI.getOperand(CurOp++);