[SelectionDAG] Peek through freeze to see XOR

Author: AZero13

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -10016,8 +10016,15 @@ SDValue DAGCombiner::visitXOR(SDNode *N) {
     }
   }
 
+  auto PeekThroughFreeze = [](SDValue N) {
+    if (N->getOpcode() == ISD::FREEZE && N.hasOneUse())
+      return N->getOperand(0);
+    return N;
+  };
+
   // fold (xor x, x) -> 0
-  if (N0 == N1)
+  // FIXME: Refactor this and sub and other similar operations together.
+  if (PeekThroughFreeze(N0) == PeekThroughFreeze(N1))
     return tryFoldToZero(DL, TLI, VT, DAG, LegalOperations);
 
   // fold (xor (shl 1, x), -1) -> (rotl ~1, x)

llvm/test/CodeGen/X86/freeze-simplify.ll

@@ -26,9 +26,6 @@ define i32 @sub_freeze_2(i32 %x, i32 %y) {
 define i32 @xor_freeze(i32 %x, i32 %y) {
 ; X86ASM-LABEL: xor_freeze:
 ; X86ASM:       # %bb.0:
-; X86ASM-NEXT:    movl %edi, %eax
-; X86ASM-NEXT:    xorl %edx, %edx
-; X86ASM-NEXT:    divl %esi
 ; X86ASM-NEXT:    xorl %eax, %eax
 ; X86ASM-NEXT:    retq
   %a = udiv i32 %x, %y