vendor/llvm/llvm-release_50-r311606

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index 29d1ba406ae4..e235e5eb1a06 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -1941,6 +1941,12 @@ Instruction *ReassociatePass::canonicalizeNegConstExpr(Instruction *I) {
   if (!User->isCommutative() && User->getOperand(1) != I)
     return nullptr;
 
+  // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
+  // resulting subtract will be broken up later.  This can get us into an
+  // infinite loop during reassociation.
+  if (UserOpcode == Instruction::FAdd && ShouldBreakUpSubtract(User))
+    return nullptr;
+
   // Change the sign of the constant.
   APFloat Val = CF->getValueAPF();
   Val.changeSign();