[AArch64] Add early exit to promoteLoadFromStore.

There should be at most a single kill flag for the
promoted operand between the store/load pair.
Discussed in https://reviews.llvm.org/D34402.

llvm-svn: 305889

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp b/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
index c35de77727e..c45c0b4c8ed 100644
--- a/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LoadStoreOptimizer.cpp
@@ -877,7 +877,10 @@ AArch64LoadStoreOpt::promoteLoadFromStore(MachineBasicBlock::iterator LoadI,
   // Clear kill flags between store and load.
   for (MachineInstr &MI : make_range(StoreI->getIterator(),
                                      BitExtMI->getIterator()))
-    MI.clearRegisterKills(StRt, TRI);
+    if (MI.killsRegister(StRt, TRI)) {
+      MI.clearRegisterKills(StRt, TRI);
+      break;
+    }
 
   DEBUG(dbgs() << "Promoting load by replacing :\n    ");
   DEBUG(StoreI->print(dbgs()));