[InstCombine] Verify CmpInst is equality in `foldICmpPow2Test`; PR63327

[goldstein.w.n]

Summary

When D152728 hoisted the code to a helper function, it moved the call
to the helper outside of foldICmpEquality, so an equality check is
needed in the helper.

[nikic]

LGTM

[fhahn]

LGTM, thanks

Please include Fixes #63327 in the commit message for GitHub to auto close

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

 }
 
 // Canonicalize checking for a power-of-2-or-zero value:
 static Instruction *foldICmpPow2Test(ICmpInst &I,
                                      InstCombiner::BuilderTy &Builder) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
   const CmpInst::Predicate Pred = I.getPredicate();
   Value *A = nullptr;
+  if (I.isEquality()) {
     // (A & (A-1)) == 0 --> ctpop(A) < 2 (two commuted variants)
     // ((A-1) & A) != 0 --> ctpop(A) > 1 (two commuted variants)
     if (!match(Op0, m_OneUse(m_c_And(m_Add(m_Value(A), m_AllOnes()),
                                      m_Deferred(A)))) ||
         !match(Op1, m_ZeroInt()))
       A = nullptr;
 
     // (A & -A) == A --> ctpop(A) < 2 (four commuted variants)
     // (-A & A) != A --> ctpop(A) > 1 (four commuted variants)
     if (match(Op0, m_OneUse(m_c_And(m_Neg(m_Specific(Op1)), m_Specific(Op1)))))
       A = Op1;
     else if (match(Op1,
                    m_OneUse(m_c_And(m_Neg(m_Specific(Op0)), m_Specific(Op0)))))
       A = Op0;
-
+  }
   if (A) {
     Type *Ty = A->getType();
     CallInst *CtPop = Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, A);
     return Pred == ICmpInst::ICMP_EQ ? new ICmpInst(ICmpInst::ICMP_ULT, CtPop,
                                                     ConstantInt::get(Ty, 2))
                                      : new ICmpInst(ICmpInst::ICMP_UGT, CtPop,
                                                     ConstantInt::get(Ty, 1));
   }

llvm/test/Transforms/InstCombine/ispow2.ll

 ; CHECK-NEXT:    ret <2 x i1> [[R]]
 ;
   %t0 = tail call <2 x i8> @llvm.ctpop.v2i8(<2 x i8> %x)
   %cmp = icmp ne <2 x i8> %t0, <i8 1, i8 1>
   %notzero = icmp ne <2 x i8> %x, <i8 0, i8 0>
   %r = or <2 x i1> %cmp, %notzero
   ret <2 x i1> %r
 }
+
+define i1 @is_pow2_fail_pr63327(i32 %x) {
+; CHECK-LABEL: @is_pow2_fail_pr63327(
+; CHECK-NEXT:    [[NX:%.*]] = sub i32 0, [[X:%.*]]
+; CHECK-NEXT:    [[X_AND_NX:%.*]] = and i32 [[NX]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp sge i32 [[X_AND_NX]], [[X]]
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %nx = sub i32 0, %x
+  %x_and_nx = and i32 %x, %nx
+  %r = icmp sge i32 %x_and_nx, %x
+  ret i1 %r
+}