Reapply r146481 with a fix to create the Builder value in the correct place and

[oota-llvm.git] / lib / CodeGen / PHIElimination.cpp

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 5f7cf582c9602b3e615ddb185cb11b043a13263e..0e52496f00c970c5977136982e3c7f3d04749591 100644 (file)
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -28,12 +28,17 @@
 #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
@@ -104,11 +109,16 @@ bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
 
   bool Changed = false;
 
+  // This pass takes the function out of SSA form.
+  MRI->leaveSSA();
+
   // 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
@@ -400,7 +410,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
     return false;   // Quick exit for basic blocks without PHIs.
 
   bool Changed = false;
-  for (MachineBasicBlock::const_iterator BBI = MBB.begin(), BBE = MBB.end();
+  for (MachineBasicBlock::iterator BBI = MBB.begin(), BBE = MBB.end();
        BBI != BBE && BBI->isPHI(); ++BBI) {
     for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) {
       unsigned Reg = BBI->getOperand(i).getReg();