Add an option to disable critical edge splitting in PHIElimination.

llvm-svn: 127398

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index 5f7cf582c96..9fd5b0e5770 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -28,12 +28,18 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include <algorithm>
 #include <map>
 using namespace llvm;
 
+static cl::opt<bool>
+DisableEdgeSplitting("disable-phi-elim-edge-splitting", cl::init(false),
+                     cl::Hidden, cl::desc("Disable critical edge splitting "
+                                          "during PHI elimination"));
+
 namespace {
   class PHIElimination : public MachineFunctionPass {
     MachineRegisterInfo *MRI; // Machine register information
@@ -105,10 +111,12 @@ bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
   bool Changed = false;
 
   // Split critical edges to help the coalescer
-  if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
-    MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
-    for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
-      Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+  if (!DisableEdgeSplitting) {
+    if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
+      MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+      for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+        Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+    }
   }
 
   // Populate VRegPHIUseCount