Rework how the non-sse2 memory barrier is lowered so that the

encoding is correct for the built-in assembler.

Based on a patch from Chris.

llvm-svn: 111083

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -7706,10 +7706,22 @@ SDValue X86TargetLowering::LowerMEMBARRIER(SDValue Op, SelectionDAG &DAG) const{
   DebugLoc dl = Op.getDebugLoc();
   
   if (!Subtarget->hasSSE2()) {
+    SDValue Chain = Op.getOperand(0);
     SDValue Zero = DAG.getConstant(0, 
                                    Subtarget->is64Bit() ? MVT::i64 : MVT::i32);
-    return DAG.getNode(X86ISD::MEMBARRIER, dl, MVT::Other, Op.getOperand(0),
+    SDValue Ops[] = {
-                       Zero);
+      DAG.getRegister(X86::ESP, MVT::i32), // Base
+      DAG.getTargetConstant(1, MVT::i8),   // Scale
+      DAG.getRegister(0, MVT::i32),        // Index
+      DAG.getTargetConstant(0, MVT::i32),  // Disp
+      DAG.getRegister(0, MVT::i32),        // Segment.
+      Zero,
+      Chain
+    };
+    SDNode *Res = 
+      DAG.getMachineNode(X86::OR32mrLocked, dl, MVT::Other, Ops,
+                          array_lengthof(Ops));
+    return SDValue(Res, 0);
   }
   
   unsigned isDev = cast<ConstantSDNode>(Op.getOperand(5))->getZExtValue();

llvm/lib/Target/X86/X86InstrInfo.td

@@ -3928,18 +3928,17 @@ def EH_RETURN   : I<0xC3, RawFrm, (outs), (ins GR32:$addr),
 //
 
 // Memory barriers
+
+// TODO: Get this to fold the constant into the instruction.           
+def OR32mrLocked  : I<0x09, MRMDestMem, (outs), (ins i32mem:$dst, GR32:$zero),
+                      "lock\n\t"
+                      "or{l}\t{$zero, $dst|$dst, $zero}",
+                      []>, Requires<[In32BitMode]>, LOCK;
+
 let hasSideEffects = 1 in {
 def Int_MemBarrier : I<0, Pseudo, (outs), (ins),
                      "#MEMBARRIER",
                      [(X86MemBarrier)]>, Requires<[HasSSE2]>;
-
-// TODO: Get this to fold the constant into the instruction.           
-let Defs = [ESP] in
-def Int_MemBarrierNoSSE  : I<0x09, MRM1r, (outs), (ins GR32:$zero),
-                           "lock\n\t"
-                           "or{l}\t{$zero, (%esp)|(%esp), $zero}",
-                           [(X86MemBarrierNoSSE GR32:$zero)]>,
- 													 Requires<[In32BitMode]>, LOCK;
 }
 
 // Atomic swap. These are just normal xchg instructions. But since a memory