X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FPeepholeOptimizer.cpp;h=9aaecacc15e968fc723365ad8823d182e5bdd4a6;hb=fb62ba2fd3f0858fbc4c982211d112a1e93f683c;hp=92daaf7a9b0d750002ebd5d6019e0fc78d47ebec;hpb=4abd22ba6bbda9156bda19f6db7528bf6cfe1fe9;p=oota-llvm.git

diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index 92daaf7a9b0..9aaecacc15e 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/lib/CodeGen/PeepholeOptimizer.cpp
@@ -354,7 +354,7 @@ namespace {
 
     /// \brief Following the use-def chain, get the next available source
     /// for the tracked value.
-    /// \return A ValueTrackerResult containing the a set of registers
+    /// \return A ValueTrackerResult containing a set of registers
     /// and sub registers with tracked values. A ValueTrackerResult with
     /// an empty set of registers means no source was found.
     ValueTrackerResult getNextSource();
@@ -632,10 +632,9 @@ bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
   SmallVector<TargetInstrInfo::RegSubRegPair, 4> SrcToLook;
   TargetInstrInfo::RegSubRegPair CurSrcPair(Reg, SubReg);
   SrcToLook.push_back(CurSrcPair);
-  bool ShouldRewrite = false;
 
-  unsigned PHILimit = RewritePHILimit;
-  while (!SrcToLook.empty() && PHILimit) {
+  unsigned PHICount = 0;
+  while (!SrcToLook.empty() && PHICount < RewritePHILimit) {
     TargetInstrInfo::RegSubRegPair Pair = SrcToLook.pop_back_val();
     // As explained above, do not handle physical registers
     if (TargetRegisterInfo::isPhysicalRegister(Pair.Reg))
@@ -645,6 +644,7 @@ bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
     ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI,
                             !DisableAdvCopyOpt, TII);
     ValueTrackerResult Res;
+    bool ShouldRewrite = false;
 
     do {
       // Follow the chain of copies until we reach the top of the use-def chain
@@ -671,7 +671,7 @@ bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
       // a PHI instruction. Add the found PHI edges to be looked up further.
       unsigned NumSrcs = Res.getNumSources();
       if (NumSrcs > 1) {
-        PHILimit--;
+        PHICount++;
         for (unsigned i = 0; i < NumSrcs; ++i)
           SrcToLook.push_back(TargetInstrInfo::RegSubRegPair(
               Res.getSrcReg(i), Res.getSrcSubReg(i)));
@@ -698,17 +698,17 @@ bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
     if (Res.isValid())
       continue;
 
-    if (!PHILimit) {
-      DEBUG(dbgs() << "findNextSource: PHI limit reached\n");
-      return false;
-    }
-
     // Do not continue searching for a new source if the there's at least
     // one use-def which cannot be rewritten.
     if (!ShouldRewrite)
       return false;
   }
 
+  if (PHICount >= RewritePHILimit) {
+    DEBUG(dbgs() << "findNextSource: PHI limit reached\n");
+    return false;
+  }
+
   // If we did not find a more suitable source, there is nothing to optimize.
   if (CurSrcPair.Reg == Reg)
     return false;
@@ -721,7 +721,7 @@ bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg,
 /// successfully traverse a PHI instruction and find suitable sources coming
 /// from its edges. By inserting a new PHI, we provide a rewritten PHI def
 /// suitable to be used in a new COPY instruction.
-MachineInstr *
+static MachineInstr *
 insertPHI(MachineRegisterInfo *MRI, const TargetInstrInfo *TII,
           const SmallVectorImpl<TargetInstrInfo::RegSubRegPair> &SrcRegs,
           MachineInstr *OrigPHI) {
@@ -847,6 +847,7 @@ public:
         continue;
       }
 
+      // TODO: remove once multiple srcs w/ coaslescable copies are supported.
       if (!HandleMultipleSources)
         break;
 
@@ -863,6 +864,9 @@ public:
       // Build the new PHI node and return its def register as the new source.
       MachineInstr *OrigPHI = const_cast<MachineInstr *>(Res.getInst());
       MachineInstr *NewPHI = insertPHI(MRI, TII, NewPHISrcs, OrigPHI);
+      DEBUG(dbgs() << "-- getNewSource\n");
+      DEBUG(dbgs() << "   Replacing: " << *OrigPHI);
+      DEBUG(dbgs() << "        With: " << *NewPHI);
       const MachineOperand &MODef = NewPHI->getOperand(0);
       return TargetInstrInfo::RegSubRegPair(MODef.getReg(), MODef.getSubReg());
 
@@ -954,6 +958,9 @@ public:
     if (Def.SubReg)
       NewCopy->getOperand(0).setIsUndef();
 
+    DEBUG(dbgs() << "-- RewriteSource\n");
+    DEBUG(dbgs() << "   Replacing: " << CopyLike);
+    DEBUG(dbgs() << "        With: " << *NewCopy);
     MRI.replaceRegWith(Def.Reg, NewVR);
     MRI.clearKillFlags(NewVR);
 
@@ -1216,7 +1223,7 @@ bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr *MI) {
     TargetInstrInfo::RegSubRegPair TrackPair(TrackReg, TrackSubReg);
     TargetInstrInfo::RegSubRegPair NewSrc = CpyRewriter->getNewSource(
         MRI, TII, TrackPair, RewriteMap, false /* multiple sources */);
-    if (SrcReg == NewSrc.Reg)
+    if (SrcReg == NewSrc.Reg || NewSrc.Reg == 0)
       continue;
 
     // Rewrite source.
@@ -1405,16 +1412,15 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
       if (MI->isDebugValue())
           continue;
 
-      // If there exists an instruction which belongs to the following
-      // categories, we will discard the load candidates.
+      // If we run into an instruction we can't fold across, discard
+      // the load candidates.
+      if (MI->isLoadFoldBarrier())
+        FoldAsLoadDefCandidates.clear();
+
       if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() ||
           MI->isKill() || MI->isInlineAsm() ||
-          MI->hasUnmodeledSideEffects()) {
-        FoldAsLoadDefCandidates.clear();
+          MI->hasUnmodeledSideEffects())
         continue;
-      }
-      if (MI->mayStore() || MI->isCall())
-        FoldAsLoadDefCandidates.clear();
 
       if ((isUncoalescableCopy(*MI) &&
            optimizeUncoalescableCopy(MI, LocalMIs)) ||
@@ -1760,7 +1766,7 @@ ValueTrackerResult ValueTracker::getNextSource() {
     Res.setInst(Def);
 
     // If we can still move up in the use-def chain, move to the next
-    // defintion.
+    // definition.
     if (!TargetRegisterInfo::isPhysicalRegister(Reg) && OneRegSrc) {
       Def = MRI.getVRegDef(Reg);
       DefIdx = MRI.def_begin(Reg).getOperandNo();