[X86] Fix an old FIXME about folding the zero constant into the OR instruction we use for sequentially consistent fence in 32-bit mode without SSE2.

llvm-svn: 350013

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -25180,7 +25180,7 @@ static SDValue LowerATOMIC_FENCE(SDValue Op, const X86Subtarget &Subtarget,
       return DAG.getNode(X86ISD::MFENCE, dl, MVT::Other, Op.getOperand(0));
 
     SDValue Chain = Op.getOperand(0);
-    SDValue Zero = DAG.getConstant(0, dl, MVT::i32);
+    SDValue Zero = DAG.getTargetConstant(0, dl, MVT::i32);
     SDValue Ops[] = {
       DAG.getRegister(X86::ESP, MVT::i32),     // Base
       DAG.getTargetConstant(1, dl, MVT::i8),   // Scale
@@ -25190,7 +25190,7 @@ static SDValue LowerATOMIC_FENCE(SDValue Op, const X86Subtarget &Subtarget,
       Zero,
       Chain
     };
-    SDNode *Res = DAG.getMachineNode(X86::OR32mrLocked, dl, MVT::Other, Ops);
+    SDNode *Res = DAG.getMachineNode(X86::OR32mi8Locked, dl, MVT::Other, Ops);
     return SDValue(Res, 0);
   }
 

llvm/lib/Target/X86/X86InstrCompiler.td

@@ -662,12 +662,11 @@ def : Pat<(v8f64 (X86cmov VR512:$t, VR512:$f, imm:$cond, EFLAGS)),
 
 // Memory barriers
 
-// TODO: Get this to fold the constant into the instruction.
 let isCodeGenOnly = 1, Defs = [EFLAGS] in
-def OR32mrLocked  : I<0x09, MRMDestMem, (outs), (ins i32mem:$dst, GR32:$zero),
-                      "or{l}\t{$zero, $dst|$dst, $zero}", []>,
-                      Requires<[Not64BitMode]>, OpSize32, LOCK,
-                      Sched<[WriteALURMW]>;
+def OR32mi8Locked  : Ii8<0x83, MRM1m, (outs), (ins i32mem:$dst, i32i8imm:$zero),
+                         "or{l}\t{$zero, $dst|$dst, $zero}", []>,
+                         Requires<[Not64BitMode]>, OpSize32, LOCK,
+                         Sched<[WriteALURMW]>;
 
 let hasSideEffects = 1 in
 def Int_MemBarrier : I<0, Pseudo, (outs), (ins),

llvm/test/CodeGen/X86/barrier.ll

@@ -4,8 +4,7 @@
 define void @test() {
 ; CHECK-LABEL: test:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    xorl %eax, %eax
-; CHECK-NEXT:    lock orl %eax, (%esp)
+; CHECK-NEXT:    lock orl $0, (%esp)
 ; CHECK-NEXT:    retl
 	fence seq_cst
 	ret void