Update the X86 disassembler to use xacquire and xrelease when appropriate.

[oota-llvm.git] / lib / Target / X86 / Disassembler / X86DisassemblerDecoder.c

diff --git a/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c b/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
index e40edba6d689e94e84a4b378fed56fffd845512e..55ab8ebe7b0b3ce7c6f4d0d7a37a274807f80dfb 100644 (file)
--- a/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
+++ b/lib/Target/X86/Disassembler/X86DisassemblerDecoder.c
@@ -328,6 +328,27 @@ static int readPrefixes(struct InternalInstruction* insn) {
         break;
       if (lookAtByte(insn, &nextByte))
         return -1;
+      /*
+       * If the byte is 0xf2 or 0xf3, and any of the following conditions are
+       * met:
+       * - it is followed by a LOCK (0xf0) prefix
+       * - it is followed by an xchg instruction
+       * then it should be disassembled as a xacquire/xrelease not repne/rep.
+       */
+      if ((byte == 0xf2 || byte == 0xf3) &&
+          ((nextByte == 0xf0) |
+          ((nextByte & 0xfe) == 0x86 || (nextByte & 0xf8) == 0x90)))
+        insn->xAcquireRelease = TRUE;
+      /*
+       * Also if the byte is 0xf3, and the following condition is met:
+       * - it is followed by a "mov mem, reg" (opcode 0x88/0x89) or
+       *                       "mov mem, imm" (opcode 0xc6/0xc7) instructions.
+       * then it should be disassembled as an xrelease not rep.
+       */
+      if (byte == 0xf3 &&
+          (nextByte == 0x88 || nextByte == 0x89 ||
+           nextByte == 0xc6 || nextByte == 0xc7))
+        insn->xAcquireRelease = TRUE;
       if (insn->mode == MODE_64BIT && (nextByte & 0xf0) == 0x40) {
         if (consumeByte(insn, &nextByte))
           return -1;