Fold (-x + -y) -> -(x+y) which promotes better association, fixing
the second half of PR2047
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47244 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index c9ff01b..1ecefeb 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2090,8 +2090,16 @@
}
// -A + B --> B - A
- if (Value *V = dyn_castNegVal(LHS))
- return BinaryOperator::createSub(RHS, V);
+ // -A + -B --> -(A + B)
+ if (Value *LHSV = dyn_castNegVal(LHS)) {
+ if (Value *RHSV = dyn_castNegVal(RHS)) {
+ Instruction *NewAdd = BinaryOperator::createAdd(LHSV, RHSV, "sum");
+ InsertNewInstBefore(NewAdd, I);
+ return BinaryOperator::createNeg(NewAdd);
+ }
+
+ return BinaryOperator::createSub(RHS, LHSV);
+ }
// A + -B --> A - B
if (!isa<Constant>(RHS))