InstCombine: Fold ((A | B) & C1) ^ (B & C2) -> (A & C1) ^ B if C1^C2=-1
Adapted from a patch by Richard Smith, test-case written by me.
llvm-svn: 216157
diff --git a/llvm/lib/Transforms/InstCombine/InstCombine.h b/llvm/lib/Transforms/InstCombine/InstCombine.h
index 9e1cc3c..c8ed7c2 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombine.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombine.h
@@ -152,6 +152,8 @@
Value *FoldOrOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
Instruction *FoldOrWithConstants(BinaryOperator &I, Value *Op, Value *A,
Value *B, Value *C);
+ Instruction *FoldXorWithConstants(BinaryOperator &I, Value *Op, Value *A,
+ Value *B, Value *C);
Instruction *visitOr(BinaryOperator &I);
Instruction *visitXor(BinaryOperator &I);
Instruction *visitShl(BinaryOperator &I);
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 743e20b..3e88bd3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1983,6 +1983,38 @@
return nullptr;
}
+/// \brief This helper function folds:
+///
+/// ((A | B) & C1) ^ (B & C2)
+///
+/// into:
+///
+/// (A & C1) ^ B
+///
+/// when the XOR of the two constants is "all ones" (-1).
+Instruction *InstCombiner::FoldXorWithConstants(BinaryOperator &I, Value *Op,
+ Value *A, Value *B, Value *C) {
+ ConstantInt *CI1 = dyn_cast<ConstantInt>(C);
+ if (!CI1)
+ return nullptr;
+
+ Value *V1 = nullptr;
+ ConstantInt *CI2 = nullptr;
+ if (!match(Op, m_And(m_Value(V1), m_ConstantInt(CI2))))
+ return nullptr;
+
+ APInt Xor = CI1->getValue() ^ CI2->getValue();
+ if (!Xor.isAllOnesValue())
+ return nullptr;
+
+ if (V1 == A || V1 == B) {
+ Value *NewOp = Builder->CreateAnd(V1 == A ? B : A, CI1);
+ return BinaryOperator::CreateXor(NewOp, V1);
+ }
+
+ return nullptr;
+}
+
Instruction *InstCombiner::visitOr(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
@@ -2165,6 +2197,18 @@
Instruction *Ret = FoldOrWithConstants(I, Op0, A, V1, D);
if (Ret) return Ret;
}
+ // ((A^B)&1)|(B&-2) -> (A&1) ^ B
+ if (match(A, m_Xor(m_Value(V1), m_Specific(B))) ||
+ match(A, m_Xor(m_Specific(B), m_Value(V1)))) {
+ Instruction *Ret = FoldXorWithConstants(I, Op1, V1, B, C);
+ if (Ret) return Ret;
+ }
+ // (B&-2)|((A^B)&1) -> (A&1) ^ B
+ if (match(B, m_Xor(m_Specific(A), m_Value(V1))) ||
+ match(B, m_Xor(m_Value(V1), m_Specific(A)))) {
+ Instruction *Ret = FoldXorWithConstants(I, Op0, A, V1, D);
+ if (Ret) return Ret;
+ }
}
// (A ^ B) | ((B ^ C) ^ A) -> (A ^ B) | C