The maximum power of 2 dividing a power of 2 is itself. This occurs
in 403.gcc and was spotted by my super-optimizer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143054 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 131cc97..d9e3400 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -1197,6 +1197,15 @@
(A == Op0 || B == Op0))
return Op0;
+ // A & (-A) = A if A is a power of two or zero.
+ if (match(Op0, m_Neg(m_Specific(Op1))) ||
+ match(Op1, m_Neg(m_Specific(Op0)))) {
+ if (isPowerOfTwo(Op0, TD, /*OrZero*/true))
+ return Op0;
+ if (isPowerOfTwo(Op1, TD, /*OrZero*/true))
+ return Op1;
+ }
+
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT,
MaxRecurse))