Add support for encoding the HLE XACQUIRE and XRELEASE prefixes.

For decoding, keep the current behavior of always decoding these as their REP
versions. In the future, this could be improved to recognize the cases where
these behave as XACQUIRE and XRELEASE and decode them as such.

llvm-svn: 184207

llvm/lib/Target/X86/X86InstrTSX.td

@@ -37,3 +37,10 @@ def XTEST : I<0x01, MRM_D6, (outs), (ins),
 def XABORT : Ii8<0xc6, MRM_F8, (outs), (ins i8imm:$imm),
                  "xabort\t$imm",
                  [(int_x86_xabort imm:$imm)]>, Requires<[HasRTM]>;
+
+// HLE prefixes
+
+def XACQUIRE_PREFIX : I<0xF2, RawFrm, (outs), (ins), "xacquire", []>, Requires<[HasHLE]>;
+
+def XRELEASE_PREFIX : I<0xF3, RawFrm, (outs), (ins), "xrelease", []>, Requires<[HasHLE]>;
+

llvm/test/MC/X86/x86_64-hle-encoding.s

@@ -0,0 +1,9 @@
+// RUN: llvm-mc -triple x86_64-unknown-unknown --show-encoding %s | FileCheck %s
+
+// CHECK: xacquire
+// CHECK: [0xf2]
+    xacquire
+
+// CHECK: xrelease
+// CHECK: [0xf3]
+    xrelease

llvm/utils/TableGen/X86RecognizableInstr.cpp

@@ -461,6 +461,12 @@ RecognizableInstr::filter_ret RecognizableInstr::filter() const {
       Name == "VMOVQs64rr")
     return FILTER_WEAK;
 
+  // XACQUIRE and XRELEASE reuse REPNE and REP respectively.
+  // For now, just prefer the REP versions.
+  if (Name == "XACQUIRE_PREFIX" ||
+      Name == "XRELEASE_PREFIX")
+    return FILTER_WEAK;
+
   if (HasFROperands && Name.find("MOV") != Name.npos &&
      ((Name.find("2") != Name.npos && Name.find("32") == Name.npos) ||
       (Name.find("to") != Name.npos)))