[InstSimplify] move (A & ~B) | (A ^ B) -> (A ^ B) from InstCombine
This is a straight cut and paste, but there's a bigger problem: if this
fold exists for simplifyOr, there should be a DeMorganized version for
simplifyAnd. But more than that, we have a patchwork of ad hoc logic
optimizations in InstCombine. There should be some structure to ensure
that we're not missing sibling folds across and/or/xor.
llvm-svn: 301213
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 2259fba..0f60f1b 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1877,6 +1877,19 @@
(A == Op0 || B == Op0))
return Constant::getAllOnesValue(Op0->getType());
+ // (A & ~B) | (A ^ B) -> (A ^ B)
+ // (~B & A) | (A ^ B) -> (A ^ B)
+ if (match(Op0, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
+ match(Op1, m_Xor(m_Specific(A), m_Specific(B))))
+ return Op1;
+
+ // Commute the 'or' operands.
+ // (A ^ B) | (A & ~B) -> (A ^ B)
+ // (A ^ B) | (~B & A) -> (A ^ B)
+ if (match(Op1, m_c_And(m_Value(A), m_Not(m_Value(B)))) &&
+ match(Op0, m_Xor(m_Specific(A), m_Specific(B))))
+ return Op0;
+
if (auto *ICILHS = dyn_cast<ICmpInst>(Op0)) {
if (auto *ICIRHS = dyn_cast<ICmpInst>(Op1)) {
if (Value *V = SimplifyOrOfICmps(ICILHS, ICIRHS))