InstCombine: Add a bunch of combines of the form x | (y ^ z).
We usually catch this kind of optimization through InstSimplify's distributive
magic, but or doesn't distribute over xor in general.
"A | ~(A | B) -> A | ~B" hits 24 times on gcc.c.
llvm-svn: 126081
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index b6b6b84..07069ad 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1897,6 +1897,47 @@
return BinaryOperator::CreateNot(And);
}
+ // Canonicalize xor to the RHS.
+ if (match(Op0, m_Xor(m_Value(), m_Value())))
+ std::swap(Op0, Op1);
+
+ // A | ( A ^ B) -> A | B
+ // A | (~A ^ B) -> A | ~B
+ if (match(Op1, m_Xor(m_Value(A), m_Value(B)))) {
+ if (Op0 == A || Op0 == B)
+ return BinaryOperator::CreateOr(A, B);
+
+ if (Op1->hasOneUse() && match(A, m_Not(m_Specific(Op0)))) {
+ Value *Not = Builder->CreateNot(B, B->getName()+".not");
+ return BinaryOperator::CreateOr(Not, Op0);
+ }
+ if (Op1->hasOneUse() && match(B, m_Not(m_Specific(Op0)))) {
+ Value *Not = Builder->CreateNot(A, A->getName()+".not");
+ return BinaryOperator::CreateOr(Not, Op0);
+ }
+ }
+
+ // A | ~(A | B) -> A | ~B
+ // A | ~(A ^ B) -> A | ~B
+ // A | ~(A & B) -> -1
+ if (match(Op1, m_Not(m_Value(A))))
+ if (BinaryOperator *B = dyn_cast<BinaryOperator>(A))
+ if (Op0 == B->getOperand(0) || Op0 == B->getOperand(1))
+ switch (B->getOpcode()) {
+ default: break;
+ case Instruction::Or:
+ case Instruction::Xor:
+ if (Op1->hasOneUse()) {
+ Value *NotOp = Op0 == B->getOperand(0) ? B->getOperand(1) :
+ B->getOperand(0);
+ Value *Not = Builder->CreateNot(NotOp, NotOp->getName()+".not");
+ return BinaryOperator::CreateOr(Not, Op0);
+ }
+ break;
+ case Instruction::And:
+ return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
+ }
+
if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
if (Value *Res = FoldOrOfICmps(LHS, RHS))