[TLI] Fold ~X >/< ~Y --> Y >/< X

Fixes: #61120 Signed-off-by: Jun Zhang <jun@junz.org> Differential Revision: https://reviews.llvm.org/D146512
llvm · Mar 23, 2023 · b3e12be · b3e12be
1 parent 1c420cd
commit b3e12be
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Showing 3 changed files with 86 additions and 113 deletions.
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -4974,6 +4974,23 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
       return DAG.getSetCC(dl, VT, N0, N1, NewCond);
   }
 
+  // ~X > ~Y --> Y > X
+  // ~X < ~Y --> Y < X
+  // ~X < C --> X > ~C
+  // ~X > C --> X < ~C
+  if ((isSignedIntSetCC(Cond) || isUnsignedIntSetCC(Cond)) &&
+      N0.getValueType().isInteger()) {
+    if (isBitwiseNot(N0)) {
+      if (isBitwiseNot(N1))
+        return DAG.getSetCC(dl, VT, N1.getOperand(0), N0.getOperand(0), Cond);
+
+      if (DAG.isConstantIntBuildVectorOrConstantInt(N1)) {
+        SDValue Not = DAG.getNOT(dl, N1, OpVT);
+        return DAG.getSetCC(dl, VT, Not, N0.getOperand(0), Cond);
+      }
+    }
+  }
+
   if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
       N0.getValueType().isInteger()) {
     if (N0.getOpcode() == ISD::ADD || N0.getOpcode() == ISD::SUB ||

diff --git a/llvm/test/CodeGen/X86/cmov.ll b/llvm/test/CodeGen/X86/cmov.ll
@@ -213,10 +213,10 @@ define i64 @test8(i64 %0, i64 %1, i64 %2) {
 define i32 @smin(i32 %x) {
 ; CHECK-LABEL: smin:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    notl %edi
 ; CHECK-NEXT:    testl %edi, %edi
+; CHECK-NEXT:    notl %edi
 ; CHECK-NEXT:    movl $-1, %eax
-; CHECK-NEXT:    cmovsl %edi, %eax
+; CHECK-NEXT:    cmovnsl %edi, %eax
 ; CHECK-NEXT:    retq
   %not_x = xor i32 %x, -1
   %1 = icmp slt i32 %not_x, -1