[X86] WaitPKG instructions

Three new instructions:

umonitor - Sets up a linear address range to be
monitored by hardware and activates the monitor.
The address range should be a writeback memory
caching type.

umwait - A hint that allows the processor to
stop instruction execution and enter an
implementation-dependent optimized state
until occurrence of a class of events.

tpause - Directs the processor to enter an
implementation-dependent optimized state
until the TSC reaches the value in EDX:EAX.

Also modifying the description of the mfence
instruction, as the rep prefix (0xF3) was allowed
before, which would conflict with umonitor during
disassembly.

Before:
$ echo 0xf3,0x0f,0xae,0xf0 | llvm-mc -disassemble
.text
mfence

After:
$ echo 0xf3,0x0f,0xae,0xf0 | llvm-mc -disassemble
.text
umonitor        %rax

Reviewers: craig.topper, zvi

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D45253

llvm-svn: 330462

1 files changed, 9 insertions, 6 deletions

diff --git a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
index 9625ebfd7aa..41c66646884 100644
--- a/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
+++ b/llvm/lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
@@ -965,8 +965,6 @@ static int getID(struct InternalInstruction* insn, const void *miiArg) {
       break;
     }
 
-    if (insn->hasAdSize)
-      attrMask |= ATTR_ADSIZE;
   }
 
   if (insn->rexPrefix & 0x08) {
@@ -1059,13 +1057,14 @@ static int getID(struct InternalInstruction* insn, const void *miiArg) {
   }
 
   /*
-   * Absolute moves need special handling.
+   * Absolute moves and umonitor need special handling.
    * -For 16-bit mode because the meaning of the AdSize and OpSize prefixes are
    *  inverted w.r.t.
    * -For 32-bit mode we need to ensure the ADSIZE prefix is observed in
    *  any position.
    */
-  if (insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0)) {
+  if ((insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0)) ||
+      (insn->opcodeType == TWOBYTE && (insn->opcode == 0xAE))) {
     /* Make sure we observed the prefixes in any position. */
     if (insn->hasAdSize)
       attrMask |= ATTR_ADSIZE;
@@ -1073,8 +1072,12 @@ static int getID(struct InternalInstruction* insn, const void *miiArg) {
       attrMask |= ATTR_OPSIZE;
 
     /* In 16-bit, invert the attributes. */
-    if (insn->mode == MODE_16BIT)
-      attrMask ^= ATTR_ADSIZE | ATTR_OPSIZE;
+    if (insn->mode == MODE_16BIT) {
+      attrMask ^= ATTR_ADSIZE;
+      /* The OpSize attribute is only valid with the absolute moves. */
+      if (insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0))
+        attrMask ^= ATTR_OPSIZE;
+    }
 
     if (getIDWithAttrMask(&instructionID, insn, attrMask))
       return -1;