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/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 5fca9c7..2cd3733 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -2885,7 +2885,7 @@
// Emit the lock opcode prefix as needed.
if (Desc->TSFlags & X86II::LOCK) ++FinalSize;
- // Emit segment overrid opcode prefix as needed.
+ // Emit segment override opcode prefix as needed.
switch (Desc->TSFlags & X86II::SegOvrMask) {
case X86II::FS:
case X86II::GS:
@@ -2943,7 +2943,7 @@
case X86II::T8: // 0F 38
++FinalSize;
break;
- case X86II::TA: // 0F 3A
+ case X86II::TA: // 0F 3A
++FinalSize;
break;
}
@@ -3087,11 +3087,15 @@
case X86II::MRM4r: case X86II::MRM5r:
case X86II::MRM6r: case X86II::MRM7r:
++FinalSize;
- // Special handling of lfence and mfence.
if (Desc->getOpcode() == X86::LFENCE ||
- Desc->getOpcode() == X86::MFENCE)
+ Desc->getOpcode() == X86::MFENCE) {
+ // Special handling of lfence and mfence;
FinalSize += sizeRegModRMByte();
- else {
+ } else if (Desc->getOpcode() == X86::MONITOR ||
+ Desc->getOpcode() == X86::MWAIT) {
+ // Special handling of monitor and mwait.
+ FinalSize += sizeRegModRMByte() + 1; // +1 for the opcode.
+ } else {
++CurOp;
FinalSize += sizeRegModRMByte();
}