Add a flag to disable the ARM64DeadRegisterDefinitionsPass

This patch adds a -arm64-dead-def-elimination flag so that it is possible to
disable dead definition elimination. Includes test case.

llvm-svn: 206207

1 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM64/ARM64TargetMachine.cpp b/llvm/lib/Target/ARM64/ARM64TargetMachine.cpp
index 101dc25839e..f4a79963790 100644
--- a/llvm/lib/Target/ARM64/ARM64TargetMachine.cpp
+++ b/llvm/lib/Target/ARM64/ARM64TargetMachine.cpp
@@ -39,6 +39,14 @@ EnableCollectLOH("arm64-collect-loh", cl::Hidden,
                           " optimization hints (LOH)"),
                  cl::init(true));
 
+static cl::opt<bool>
+EnableDeadRegisterElimination("arm64-dead-def-elimination", cl::Hidden,
+                              cl::desc("Enable the pass that removes dead"
+                                       " definitons and replaces stores to"
+                                       " them with stores to the zero"
+                                       " register"),
+                              cl::init(true));
+
 extern "C" void LLVMInitializeARM64Target() {
   // Register the target.
   RegisterTargetMachine<ARM64TargetMachine> X(TheARM64Target);
@@ -135,7 +143,8 @@ bool ARM64PassConfig::addPreRegAlloc() {
 
 bool ARM64PassConfig::addPostRegAlloc() {
   // Change dead register definitions to refer to the zero register.
-  addPass(createARM64DeadRegisterDefinitions());
+  if (EnableDeadRegisterElimination)
+    addPass(createARM64DeadRegisterDefinitions());
   return true;
 }