Revert r55467; it causes regressions in UnitTests/Vector/divides,

Benchmarks/sim/sim, and others on x86-64.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55475 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 61 deletions

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 08c0ab3c54..897eb71030 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -38,7 +38,6 @@ STATISTIC(numJoins    , "Number of interval joins performed");
 STATISTIC(numSubJoins , "Number of subclass joins performed");
 STATISTIC(numCommutes , "Number of instruction commuting performed");
 STATISTIC(numExtends  , "Number of copies extended");
-STATISTIC(NumReMats   , "Number of instructions re-materialized");
 STATISTIC(numPeep     , "Number of identity moves eliminated after coalescing");
 STATISTIC(numAborts   , "Number of times interval joining aborted");
 
@@ -427,43 +426,6 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
   return true;
 }
 
-/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
-/// computation, replace the copy by rematerialize the definition.
-bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
-                                                       unsigned DstReg,
-                                                       MachineInstr *CopyMI) {
-  unsigned CopyIdx = li_->getUseIndex(li_->getInstructionIndex(CopyMI));
-  LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
-  if (SrcLR == SrcInt.end()) // Should never happen!
-    return false;
-  VNInfo *ValNo = SrcLR->valno;
-  // If other defs can reach uses of this def, then it's not safe to perform
-  // the optimization.
-  if (ValNo->def == ~0U || ValNo->def == ~1U || ValNo->hasPHIKill)
-    return false;
-  MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
-  const TargetInstrDesc &TID = DefMI->getDesc();
-  if (!TID.isAsCheapAsAMove())
-    return false;
-  bool SawStore = false;
-  if (!DefMI->isSafeToMove(tii_, SawStore))
-    return false;
-
-  unsigned DefIdx = li_->getDefIndex(CopyIdx);
-  const LiveRange *DLR= li_->getInterval(DstReg).getLiveRangeContaining(DefIdx);
-  DLR->valno->copy = NULL;
-
-  MachineBasicBlock::iterator MII = CopyMI;
-  MachineBasicBlock *MBB = CopyMI->getParent();
-  tii_->reMaterialize(*MBB, MII, DstReg, DefMI);
-  MachineInstr *NewMI = prior(MII);
-  li_->ReplaceMachineInstrInMaps(CopyMI, NewMI);
-  CopyMI->eraseFromParent();
-  ReMatCopies.insert(CopyMI);
-  ++NumReMats;
-  return true;
-}
-
 /// isBackEdgeCopy - Returns true if CopyMI is a back edge copy.
 ///
 bool SimpleRegisterCoalescing::isBackEdgeCopy(MachineInstr *CopyMI,
@@ -513,17 +475,6 @@ SimpleRegisterCoalescing::UpdateRegDefsUses(unsigned SrcReg, unsigned DstReg,
       unsigned UseDstReg = DstReg;
       if (OldSubIdx)
           UseDstReg = tri_->getSubReg(DstReg, OldSubIdx);
-
-      unsigned CopySrcReg, CopyDstReg;
-      if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg) &&
-          CopySrcReg != CopyDstReg &&
-          CopySrcReg == SrcReg && CopyDstReg != UseDstReg) {
-        // If the use is a copy and it won't be coalesced away, and its source
-        // is defined by a trivial computation, try to rematerialize it instead.
-        if (ReMaterializeTrivialDef(li_->getInterval(SrcReg), CopyDstReg,UseMI))
-          continue;
-      }
-
       O.setReg(UseDstReg);
       O.setSubReg(0);
     } else {
@@ -914,7 +865,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
   MachineInstr *CopyMI = TheCopy.MI;
 
   Again = false;
-  if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
+  if (JoinedCopies.count(CopyMI))
     return false; // Already done.
 
   DOUT << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI;
@@ -1157,12 +1108,6 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
 
   if (!isEmpty && !JoinIntervals(DstInt, SrcInt, Swapped)) {
     // Coalescing failed.
-
-    // If definition of source is defined by trivial computation, try
-    // rematerializing it.
-    if (!isExtSubReg && !isInsSubReg &&
-        ReMaterializeTrivialDef(SrcInt, DstInt.reg, CopyMI))
-      return true;
     
     // If we can eliminate the copy without merging the live ranges, do so now.
     if (!isExtSubReg && !isInsSubReg &&
@@ -1266,6 +1211,9 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
   if (TargetRegisterInfo::isVirtualRegister(DstReg))
     RemoveUnnecessaryKills(DstReg, *ResDstInt);
 
+  // SrcReg is guarateed to be the register whose live interval that is
+  // being merged.
+  li_->removeInterval(SrcReg);
   if (isInsSubReg)
     // Avoid:
     // r1024 = op
@@ -1275,10 +1223,6 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     RemoveDeadImpDef(DstReg, *ResDstInt);
   UpdateRegDefsUses(SrcReg, DstReg, SubIdx);
 
-  // SrcReg is guarateed to be the register whose live interval that is
-  // being merged.
-  li_->removeInterval(SrcReg);
-
   if (isEmpty) {
     // Now the copy is being coalesced away, the val# previously defined
     // by the copy is being defined by an IMPLICIT_DEF which defines a zero
@@ -2074,7 +2018,6 @@ void SimpleRegisterCoalescing::printRegName(unsigned reg) const {
 
 void SimpleRegisterCoalescing::releaseMemory() {
   JoinedCopies.clear();
-  ReMatCopies.clear();
 }
 
 static bool isZeroLengthInterval(LiveInterval *li) {