- instcombine demorgan's law: and (not A), (not B) == not (or A, B)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3495 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 0f8ae0c..14a13fe 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -81,6 +81,8 @@
// in the program. Add the new instruction to the worklist.
//
void InsertNewInstBefore(Instruction *New, Instruction &Old) {
+ assert(New && New->getParent() == 0 &&
+ "New instruction already inserted into a basic block!");
BasicBlock *BB = Old.getParent();
BB->getInstList().insert(&Old, New); // Insert inst
WorkList.push_back(New); // Add to worklist
@@ -292,6 +294,16 @@
if (RHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op0);
+ // and (not A), (not B) == not (or A, B)
+ if (Op0->use_size() == 1 && Op1->use_size() == 1)
+ if (Value *A = dyn_castNotInst(Op0))
+ if (Value *B = dyn_castNotInst(Op1)) {
+ Instruction *Or = BinaryOperator::create(Instruction::Or, A, B,
+ I.getName()+".demorgan");
+ InsertNewInstBefore(Or, I);
+ return BinaryOperator::createNot(Or, I.getName());
+ }
+
return Changed ? &I : 0;
}