[Autobackout][FunctionalRegression]Revert of change: 5e0b327: Match and fold whole region override chains in VC

When the vector is overwritten by a series of wrregion instructions, and
    then inserted into a larger vector, VC can replace the initial chain
    of wrregion instructions with an alternative chain that writes the data
    directly into the larger vector.

    This transformation eliminates false data dependencies and unnecessary
    MOV instructions.

Author: sys-igc

IGC/VectorCompiler/lib/GenXCodeGen/GenXPatternMatch.cpp

@@ -49,8 +49,6 @@ SPDX-License-Identifier: MIT
 #include "GenXTargetMachine.h"
 #include "GenXUtil.h"
 #include "GenXVectorDecomposer.h"
-
-#include "llvm/ADT/IntervalMap.h"
 #include "llvm/ADT/PostOrderIterator.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/ConstantFolding.h"
@@ -64,6 +62,7 @@ SPDX-License-Identifier: MIT
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/InstVisitor.h"
+#include "llvmWrapper/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/PatternMatch.h"
@@ -78,10 +77,9 @@ SPDX-License-Identifier: MIT
 #include "llvmWrapper/ADT/APInt.h"
 #include "llvmWrapper/IR/Constants.h"
 #include "llvmWrapper/IR/DerivedTypes.h"
-#include "llvmWrapper/IR/Instructions.h"
 #include "llvmWrapper/Support/TypeSize.h"
-#include "llvmWrapper/Transforms/Utils/BasicBlockUtils.h"
 #include "llvmWrapper/Transforms/Utils/Local.h"
+#include "llvmWrapper/Transforms/Utils/BasicBlockUtils.h"
 
 #include "vc/Utils/GenX/Intrinsics.h"
 #include "vc/Utils/General/InstRebuilder.h"
@@ -186,7 +184,7 @@ class GenXPatternMatch : public FunctionPass,
   bool foldBoolAnd(Instruction *Inst);
   bool simplifyPredRegion(CallInst *Inst);
   bool simplifyWrRegion(CallInst *Inst);
-  bool simplifyRdRegion(CallInst *Inst);
+  bool simplifyRdRegion(CallInst* Inst);
   bool simplifyTruncSat(CallInst *Inst);
   bool simplifySelect(Function *F);
   bool mergeLscLoad(Function *F);
@@ -208,15 +206,6 @@ class GenXPatternMatch : public FunctionPass,
   bool matchPredAny(CallInst *Inst) const;
 
   bool matchBFN(Function &F);
-
-  bool foldWriteRegion(Function &F);
-  bool propagateWriteRegionChain(CallInst *Inst, ArrayRef<CallInst *> Chain);
-  SmallVector<CallInst *, 4> getFullOverrideChain(CallInst *Inst);
-
-  using IntervalMapTy =
-      IntervalMap<unsigned, bool, 8, IntervalMapHalfOpenInfo<unsigned>>;
-  IntervalMapTy::Allocator Alloc;
-  SmallPtrSet<Instruction *, 8> VisitedWrRegions;
 };
 
 } // namespace
@@ -252,7 +241,6 @@ bool GenXPatternMatch::runOnFunction(Function &F) {
     loadPhiConstants(F, DT, *ST, *DL, true);
     Changed |= distributeIntegerMul(&F);
     Changed |= propagateFoldableRegion(&F);
-    Changed |= foldWriteRegion(F);
     Changed |= reassociateIntegerMad(&F);
   }
 
@@ -2949,147 +2937,6 @@ bool GenXPatternMatch::simplifyWrRegion(CallInst *Inst) {
   return false;
 }
 
-bool GenXPatternMatch::foldWriteRegion(Function &F) {
-  using namespace GenXIntrinsic::GenXRegion;
-  if (vc::requiresStackCall(&F) || ST->hasFusedEU())
-    return false;
-
-  bool Changed = false;
-  SmallVector<Instruction *> ToErase;
-
-  for (auto &BB : F) {
-    for (auto &I : reverse(BB)) {
-      if (!GenXIntrinsic::isWrRegion(&I) || I.use_empty())
-        continue;
-
-      auto *InsertTo = I.getOperand(OldValueOperandNum);
-      while (auto *Cast = dyn_cast<BitCastInst>(InsertTo))
-        InsertTo = Cast->getOperand(0);
-
-      // If the wrregion destination is a load instruction, than it's the access
-      // to the _GENX_VOLATILE_ object. We shouldn't optimize it.
-      if (isa_and_nonnull<LoadInst>(InsertTo))
-        continue;
-
-      auto *Inst = cast<CallInst>(&I);
-      auto WholeChain = getFullOverrideChain(Inst);
-      if (WholeChain.empty())
-        continue;
-
-      Changed = true;
-
-      auto *DropDep = WholeChain.back();
-      DropDep->setArgOperand(OldValueOperandNum,
-                             UndefValue::get(DropDep->getType()));
-
-      // Check if the whole chain is inserted into some other region
-      if (propagateWriteRegionChain(Inst, WholeChain)) {
-        ToErase.push_back(Inst);
-        append_range(ToErase, WholeChain);
-      }
-    }
-  }
-
-  for (auto *I : ToErase) {
-    if (I->use_empty())
-      I->eraseFromParent();
-  }
-
-  VisitedWrRegions.clear();
-  return Changed;
-}
-
-bool GenXPatternMatch::propagateWriteRegionChain(CallInst *Inst,
-                                                 ArrayRef<CallInst *> Chain) {
-  using namespace GenXIntrinsic::GenXRegion;
-  IGC_ASSERT(GenXIntrinsic::isWrRegion(Inst));
-
-  auto R = genx::makeRegionWithOffset(Inst);
-  if (R.Indirect || !R.isContiguous())
-    return false;
-
-  auto *Pred = dyn_cast<Constant>(Inst->getOperand(PredicateOperandNum));
-  if (!Pred || !Pred->isAllOnesValue())
-    return false;
-
-  auto *Insert = Inst->getOperand(OldValueOperandNum);
-
-  for (auto *I : reverse(Chain)) {
-    auto *Src = I->getOperand(NewValueOperandNum);
-    auto Rgn = genx::makeRegionWithOffset(I);
-    Rgn.Offset += R.Offset;
-
-    Insert = Rgn.createWrRegion(Insert, Src, "", Inst, Inst->getDebugLoc());
-    VisitedWrRegions.insert(cast<CallInst>(Insert));
-    LLVM_DEBUG(dbgs() << "Propagating wrregion instruction: " << *Insert
-                      << "\n");
-  }
-
-  Inst->replaceAllUsesWith(Insert);
-  return true;
-}
-
-SmallVector<CallInst *, 4>
-GenXPatternMatch::getFullOverrideChain(CallInst *Inst) {
-  using namespace GenXIntrinsic::GenXRegion;
-  IGC_ASSERT(GenXIntrinsic::isWrRegion(Inst));
-
-  // Stores the intevals, that are overwritten by each particular wrregion
-  IntervalMapTy Intervals(Alloc);
-  SmallVector<CallInst *, 4> Chain;
-
-  auto *Curr = dyn_cast<CallInst>(Inst->getArgOperand(NewValueOperandNum));
-  if (!Curr)
-    return {};
-
-  auto *Ty = Curr->getType();
-  auto Size = DL->getTypeStoreSize(Ty);
-
-  bool IsOverwrite = false;
-  while (!IsOverwrite && Curr && GenXIntrinsic::isWrRegion(Curr)) {
-    if (VisitedWrRegions.contains(Curr))
-      break;
-
-    LLVM_DEBUG(dbgs() << "Looking for wrregion chain: " << *Curr << "\n");
-    auto R = genx::makeRegionWithOffset(Curr);
-    if (R.Indirect || !R.isContiguous())
-      break;
-
-    auto *Cond = dyn_cast<Constant>(Curr->getOperand(PredicateOperandNum));
-    if (!Cond || !Cond->isAllOnesValue())
-      break;
-
-    unsigned Start = R.Offset;
-    unsigned End = Start + R.NumElements * R.ElementBytes;
-
-    // Do not allow overlapping regions
-    if (Intervals.overlaps(Start, End))
-      break;
-
-    LLVM_DEBUG(dbgs() << "  Overwriting [" << Start << ", " << End << ")\n");
-    Intervals.insert(Start, End, true);
-
-    VisitedWrRegions.insert(Curr);
-    Chain.push_back(Curr);
-
-    auto *Next = Curr->getOperand(OldValueOperandNum);
-
-    // Whole region is covered, no need to continue
-    auto FirstIt = Intervals.begin();
-    IsOverwrite = isa<UndefValue>(Next) ||
-                  (FirstIt.start() == 0 && FirstIt.stop() == Size);
-
-    Curr = dyn_cast<CallInst>(Next);
-    if (!Next->hasOneUse())
-      break;
-  }
-
-  if (!IsOverwrite)
-    return {};
-
-  return Chain;
-}
-
 // Simplify (trunc.sat (ext V)) to (trunc.sat V). Even if the source and
 // destination has the same type, it's incorrect to fold them into V directly
 // as the saturation is necessary.