Split up subtracts into add+negate if they have a reassociable use or operand
that is also a subtract. This implements PR2047 and Transforms/Reassociate/subtest2.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47241 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index d0537ea..bec91db 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -399,13 +399,16 @@
return false;
// Don't bother to break this up unless either the LHS is an associable add or
- // if this is only used by one.
- if (isReassociableOp(Sub->getOperand(0), Instruction::Add))
+ // subtract or if this is only used by one.
+ if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
+ isReassociableOp(Sub->getOperand(0), Instruction::Sub))
return true;
- if (isReassociableOp(Sub->getOperand(1), Instruction::Add))
+ if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
+ isReassociableOp(Sub->getOperand(0), Instruction::Sub))
return true;
-
- if (Sub->hasOneUse() && isReassociableOp(Sub->use_back(), Instruction::Add))
+ if (Sub->hasOneUse() &&
+ (isReassociableOp(Sub->use_back(), Instruction::Add) ||
+ isReassociableOp(Sub->use_back(), Instruction::Sub)))
return true;
return false;