From 148341cc9b60d7d88be9c07a2b32b436e0cd301d Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Tue, 17 Aug 2010 21:00:37 +0000
Subject: [PATCH] PHI elimination shouldn't require machineloopinfo since it's
 used at -O0. Move the requirement to LiveIntervalAnalysis instead. Note this
 does not change the number of times machineloopinfo is computed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111285 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LiveIntervalAnalysis.cpp |  5 +++--
 lib/CodeGen/PHIElimination.cpp       | 16 +++++++++-------
 lib/CodeGen/PHIElimination.h         |  3 +--
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 21563c4f9a1..2726fc33753 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -62,9 +62,10 @@ void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
   AU.addRequired<AliasAnalysis>();
   AU.addPreserved<AliasAnalysis>();
-  AU.addPreserved<LiveVariables>();
   AU.addRequired<LiveVariables>();
-  AU.addPreservedID(MachineLoopInfoID);
+  AU.addPreserved<LiveVariables>();
+  AU.addRequired<MachineLoopInfo>();
+  AU.addPreserved<MachineLoopInfo>();
   AU.addPreservedID(MachineDominatorsID);
 
   if (!StrongPHIElim) {
diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 11566c2d866..6595bb98415 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -45,22 +45,22 @@ char &llvm::PHIEliminationID = PHIElimination::ID;
 
 void llvm::PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addPreserved<LiveVariables>();
-  AU.addRequired<MachineLoopInfo>();
   AU.addPreserved<MachineDominatorTree>();
-  AU.addPreservedID(MachineLoopInfoID);
+  AU.addPreserved<MachineLoopInfo>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &MF) {
   MRI = &MF.getRegInfo();
-  MLI = getAnalysisIfAvailable<MachineLoopInfo>();
 
   bool Changed = false;
 
   // Split critical edges to help the coalescer
-  if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>())
+  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);
+      Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+  }
 
   // Populate VRegPHIUseCount
   analyzePHINodes(MF);
@@ -380,7 +380,8 @@ void llvm::PHIElimination::analyzePHINodes(const MachineFunction& MF) {
 
 bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
                                          MachineBasicBlock &MBB,
-                                         LiveVariables &LV) {
+                                         LiveVariables &LV,
+                                         MachineLoopInfo *MLI) {
   if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
     return false;   // Quick exit for basic blocks without PHIs.
 
@@ -397,7 +398,8 @@ bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
       // out-of-line blocks into the loop which is very bad for code placement.
       if (PreMBB != &MBB &&
           !LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB)) {
-        if (!(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) &&
+        if (!MLI ||
+            !(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) &&
               MLI->isLoopHeader(&MBB)))
           Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0;
       }
diff --git a/lib/CodeGen/PHIElimination.h b/lib/CodeGen/PHIElimination.h
index b054732dace..45a97182e71 100644
--- a/lib/CodeGen/PHIElimination.h
+++ b/lib/CodeGen/PHIElimination.h
@@ -24,7 +24,6 @@ namespace llvm {
   /// Lower PHI instructions to copies.  
   class PHIElimination : public MachineFunctionPass {
     MachineRegisterInfo *MRI; // Machine register information
-    MachineLoopInfo     *MLI;
 
   public:
     static char ID; // Pass identification, replacement for typeid
@@ -52,7 +51,7 @@ namespace llvm {
 
     /// Split critical edges where necessary for good coalescer performance.
     bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
-                       LiveVariables &LV);
+                       LiveVariables &LV, MachineLoopInfo *MLI);
 
     /// SplitCriticalEdge - Split a critical edge from A to B by
     /// inserting a new MBB. Update branches in A and PHI instructions