ConstantInt *C2;
if (match(Op1, m_Add(m_Value(X), m_ConstantInt(C2))))
return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
+
+ if (SimplifyDemandedInstructionBits(I))
+ return &I;
}
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
}
+
// Otherwise just hand the sub off to ComputeMaskedBits to fill in
// the known zeros and ones.
ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
+
+ // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
+ // zero.
+ if (ConstantInt *C0 = dyn_cast<ConstantInt>(I->getOperand(0))) {
+ APInt I0 = C0->getValue();
+ if ((I0 + 1).isPowerOf2() && (I0 | KnownZero).isAllOnesValue()) {
+ Instruction *Xor = BinaryOperator::CreateXor(I->getOperand(1), C0);
+ return InsertNewInstWith(Xor, *I);
+ }
+ }
break;
case Instruction::Shl:
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
--- /dev/null
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+define i32 @test1(i32 %x) nounwind {
+ %and = and i32 %x, 31
+ %sub = sub i32 63, %and
+ ret i32 %sub
+
+; CHECK: @test1
+; CHECK-NEXT: and i32 %x, 31
+; CHECK-NEXT: xor i32 %and, 63
+; CHECK-NEXT: ret
+}