From 1acb17cb8392dce33079fe45f383944ec6616757 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sat, 2 Sep 2006 05:32:53 +0000
Subject: [PATCH] Iteration is required for some cases, even if they don't
 occur in crafty. Restore it, which re-fixes X86/2006-08-21-ExtraMovInst.ll

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30050 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/LiveIntervalAnalysis.h | 18 ++++++++--
 lib/CodeGen/LiveIntervalAnalysis.cpp        | 37 +++++++++++++--------
 2 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 030b3cfea04..4b31766285b 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -53,6 +53,17 @@ namespace llvm {
     std::vector<bool> allocatableRegs_;
 
   public:
+    struct CopyRec {
+      MachineInstr *MI;
+      unsigned SrcReg, DstReg;
+    };
+    CopyRec getCopyRec(MachineInstr *MI, unsigned SrcReg, unsigned DstReg) {
+      CopyRec R;
+      R.MI = MI;
+      R.SrcReg = SrcReg;
+      R.DstReg = DstReg;
+      return R;
+    }
     struct InstrSlots {
       enum {
         LOAD  = 0,
@@ -150,9 +161,10 @@ namespace llvm {
     /// joinIntervals - join compatible live intervals
     void joinIntervals();
 
-    /// CopyCoallesceInMBB - Coallsece copies in the specified MBB.
-    void CopyCoallesceInMBB(MachineBasicBlock *MBB);
-
+    /// CopyCoallesceInMBB - Coallsece copies in the specified MBB, putting
+    /// copies that cannot yet be coallesced into the "TryAgain" list.
+    void CopyCoallesceInMBB(MachineBasicBlock *MBB,
+                            std::vector<CopyRec> &TryAgain);
     /// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
     /// which are the src/dst of the copy instruction CopyMI.  This returns true
     /// if the copy was successfully coallesced away, or if it is never possible
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 5f010a6070a..fc9015ee999 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -883,12 +883,6 @@ static unsigned ComputeUltimateVN(unsigned VN,
   return ThisValNoAssignments[VN] = UltimateVN;
 }
 
-Statistic<> A("x", "a");
-Statistic<> B("x", "b");
-Statistic<> C("x", "c");
-Statistic<> D("x", "d");
-
-
 static bool InVector(unsigned Val, const SmallVector<unsigned, 8> &V) {
   return std::find(V.begin(), V.end(), Val) != V.end();
 }
@@ -1048,13 +1042,11 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
       } else {
         RHSValNoInfo = RHS.getValNumInfo(0);
       }
-      ++A;
     } else {
       // It was defined as a copy from the LHS, find out what value # it is.
       unsigned ValInst = RHS.getInstForValNum(0);
       RHSValID = LHS.getLiveRangeContaining(ValInst-1)->ValId;
       RHSValNoInfo = LHS.getValNumInfo(RHSValID);
-      ++B;
     }
     
     LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
@@ -1093,7 +1085,6 @@ bool LiveIntervals::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS) {
     RHSValNoAssignments[0] = RHSValID;
     
   } else {
-    ++D;
     // Loop over the value numbers of the LHS, seeing if any are defined from
     // the RHS.
     SmallVector<int, 16> LHSValsDefinedFromRHS;
@@ -1223,7 +1214,8 @@ namespace {
 }
 
 
-void LiveIntervals::CopyCoallesceInMBB(MachineBasicBlock *MBB) {
+void LiveIntervals::CopyCoallesceInMBB(MachineBasicBlock *MBB,
+                                       std::vector<CopyRec> &TryAgain) {
   DEBUG(std::cerr << ((Value*)MBB->getBasicBlock())->getName() << ":\n");
   
   for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
@@ -1234,7 +1226,8 @@ void LiveIntervals::CopyCoallesceInMBB(MachineBasicBlock *MBB) {
     unsigned SrcReg, DstReg;
     if (!tii_->isMoveInstr(*Inst, SrcReg, DstReg)) continue;
     
-    JoinCopy(Inst, SrcReg, DstReg);
+    if (!JoinCopy(Inst, SrcReg, DstReg))
+      TryAgain.push_back(getCopyRec(Inst, SrcReg, DstReg));
   }
 }
 
@@ -1242,12 +1235,14 @@ void LiveIntervals::CopyCoallesceInMBB(MachineBasicBlock *MBB) {
 void LiveIntervals::joinIntervals() {
   DEBUG(std::cerr << "********** JOINING INTERVALS ***********\n");
 
+  std::vector<CopyRec> TryAgainList;
+  
   const LoopInfo &LI = getAnalysis<LoopInfo>();
   if (LI.begin() == LI.end()) {
     // If there are no loops in the function, join intervals in function order.
     for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
          I != E; ++I)
-      CopyCoallesceInMBB(I);
+      CopyCoallesceInMBB(I, TryAgainList);
   } else {
     // Otherwise, join intervals in inner loops before other intervals.
     // Unfortunately we can't just iterate over loop hierarchy here because
@@ -1262,7 +1257,23 @@ void LiveIntervals::joinIntervals() {
 
     // Finally, join intervals in loop nest order.
     for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
-      CopyCoallesceInMBB(MBBs[i].second);
+      CopyCoallesceInMBB(MBBs[i].second, TryAgainList);
+  }
+  
+  // Joining intervals can allow other intervals to be joined.  Iteratively join
+  // until we make no progress.
+  bool ProgressMade = true;
+  while (ProgressMade) {
+    ProgressMade = false;
+
+    for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
+      CopyRec &TheCopy = TryAgainList[i];
+      if (TheCopy.MI &&
+          JoinCopy(TheCopy.MI, TheCopy.SrcReg, TheCopy.DstReg)) {
+        TheCopy.MI = 0;   // Mark this one as done.
+        ProgressMade = true;
+      }
+    }
   }
   
   DEBUG(std::cerr << "*** Register mapping ***\n");