[InstCombine] Extend (icmp eq/ne (and Z, X), (and Z, Y))

Only require one of the `and` ops to be single-use if both `X` / `Y`
are constant.

Author: goldsteinn

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -5587,7 +5587,13 @@ Instruction *InstCombinerImpl::foldICmpEquality(ICmpInst &I) {
                             ConstantInt::get(Z->getType(), CMask + CMask));
       }
 
-      if (Op0->hasOneUse() && Op1->hasOneUse()) {
+      // If either Op0/Op1 are both one use or X^Y will constant fold and one of
+      // Op0/Op1 are one use proceeed. In those cases we are instruction neutral
+      // but icmp eq/ne A, 0 is easier to analyze than icmp eq/ne A, B
+      int UseCnt =
+          int(Op0->hasOneUse()) + int(Op1->hasOneUse()) +
+          (int(match(X, m_ImmConstant()) && match(Y, m_ImmConstant())));
+      if (UseCnt >= 2) {
         // Build (X^Y) & Z
         Op1 = Builder.CreateXor(X, Y);
         Op1 = Builder.CreateAnd(Op1, Z);

llvm/test/Transforms/InstCombine/and-compare.ll

@@ -147,10 +147,9 @@ define i1 @test_ne_cp2_other_fail2(i8 %x, i8 %yy) {
 
 define i1 @test_ne_cp2_other_okay(i8 %x, i8 %yy) {
 ; CHECK-LABEL: @test_ne_cp2_other_okay(
-; CHECK-NEXT:    [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -17
-; CHECK-NEXT:    [[AND_X_Y:%.*]] = and i8 [[X]], 16
+; CHECK-NEXT:    [[AND_X_Y:%.*]] = and i8 [[X:%.*]], 16
 ; CHECK-NEXT:    call void @use.i8(i8 [[AND_X_Y]])
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[AND_X_NEG_Y]], [[AND_X_Y]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[X]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %and_x_neg_y = and i8 %x, -17
@@ -162,10 +161,9 @@ define i1 @test_ne_cp2_other_okay(i8 %x, i8 %yy) {
 
 define i1 @test_ne_cp2_other_okay2(i8 %x, i8 %yy) {
 ; CHECK-LABEL: @test_ne_cp2_other_okay2(
-; CHECK-NEXT:    [[AND_X_NEG_Y:%.*]] = and i8 [[X:%.*]], -17
-; CHECK-NEXT:    [[AND_X_Y:%.*]] = and i8 [[X]], 16
+; CHECK-NEXT:    [[AND_X_Y:%.*]] = and i8 [[X:%.*]], 16
 ; CHECK-NEXT:    call void @use.i8(i8 [[AND_X_Y]])
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[AND_X_Y]], [[AND_X_NEG_Y]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[X]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %and_x_neg_y = and i8 %x, -17