Rewrite #3 of machine block placement. This is based somewhat on the

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

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 2ed1c38d4558ef68c0c0a85d9f115cad6385fdde..6994aa58fbd5459099b3e5e5946e906eb3f79071 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
@@ -83,6 +88,7 @@ namespace {
 }
 
 STATISTIC(NumAtomic, "Number of atomic phis lowered");
+STATISTIC(NumCriticalEdgesSplit, "Number of critical edges split");
 STATISTIC(NumReused, "Number of reused lowered phis");
 
 char PHIElimination::ID = 0;
@@ -103,11 +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
@@ -211,7 +222,7 @@ void PHIElimination::LowerAtomicPHINode(
       IncomingReg = entry;
       reusedIncoming = true;
       ++NumReused;
-      DEBUG(dbgs() << "Reusing %reg" << IncomingReg << " for " << *MPhi);
+      DEBUG(dbgs() << "Reusing " << PrintReg(IncomingReg) << " for " << *MPhi);
     } else {
       const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg);
       entry = IncomingReg = MF.getRegInfo().createVirtualRegister(RC);
@@ -339,6 +350,8 @@ void PHIElimination::LowerAtomicPHINode(
 #ifndef NDEBUG
         for (MachineBasicBlock::iterator TI = llvm::next(Term);
              TI != opBlock.end(); ++TI) {
+          if (TI->isDebugValue())
+            continue;
           assert(!TI->readsRegister(SrcReg) &&
                  "Terminator instructions cannot use virtual registers unless"
                  "they are the first terminator in a block!");
@@ -347,9 +360,13 @@ void PHIElimination::LowerAtomicPHINode(
       } else if (reusedIncoming || !IncomingReg) {
         // We may have to rewind a bit if we didn't insert a copy this time.
         KillInst = Term;
-        while (KillInst != opBlock.begin())
-          if ((--KillInst)->readsRegister(SrcReg))
+        while (KillInst != opBlock.begin()) {
+          --KillInst;
+          if (KillInst->isDebugValue())
+            continue;
+          if (KillInst->readsRegister(SrcReg))
             break;
+        }
       } else {
         // We just inserted this copy.
         KillInst = prior(InsertPos);
@@ -386,9 +403,9 @@ void PHIElimination::analyzePHINodes(const MachineFunction& MF) {
 }
 
 bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
-                                         MachineBasicBlock &MBB,
-                                         LiveVariables &LV,
-                                         MachineLoopInfo *MLI) {
+                                   MachineBasicBlock &MBB,
+                                   LiveVariables &LV,
+                                   MachineLoopInfo *MLI) {
   if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
     return false;   // Quick exit for basic blocks without PHIs.
 
@@ -407,10 +424,14 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
           !LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB)) {
         if (!MLI ||
             !(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) &&
-              MLI->isLoopHeader(&MBB)))
-          Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0;
+              MLI->isLoopHeader(&MBB))) {
+          if (PreMBB->SplitCriticalEdge(&MBB, this)) {
+            Changed = true;
+            ++NumCriticalEdgesSplit;
+          }
+        }
       }
     }
   }
-  return true;
+  return Changed;
 }