It is possible for several constants which aren't individually absorbing to
combine to the absorbing element. Thanks to nbjoerg on IRC for pointing this
out.
llvm-svn: 158399
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index ed7340f..66fa074 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -629,8 +629,13 @@
// Add any constants back into Ops, all globbed together and reduced to having
// weight 1 for the convenience of users.
Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
- if (Cst && Cst != Identity)
+ if (Cst && Cst != Identity) {
+ // If combining multiple constants resulted in the absorber then the entire
+ // expression must evaluate to the absorber.
+ if (Cst == Absorber)
+ Ops.clear();
Ops.push_back(std::make_pair(Cst, APInt(Bitwidth, 1)));
+ }
// For nilpotent operations or addition there may be no operands, for example
// because the expression was "X xor X" or consisted of 2^Bitwidth additions: