Revert 91280-91283, 91286-91289, 91291, 91293, 91295-91296. It apparently introduced a non-deterministic behavior in the optimizer somewhere.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91598 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 70 insertions, 30 deletions

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 8c2e9b6ff5..600937693b 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -24,14 +24,18 @@
 #include "llvm/Constants.h"
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
+#include "llvm/Type.h"
 #include "llvm/DerivedTypes.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/IVUsers.h"
+#include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/Transforms/Utils/AddrModeMatcher.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CFG.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ValueHandle.h"
@@ -81,6 +85,8 @@ namespace {
 
   class LoopStrengthReduce : public LoopPass {
     IVUsers *IU;
+    LoopInfo *LI;
+    DominatorTree *DT;
     ScalarEvolution *SE;
     bool Changed;
 
@@ -88,6 +94,10 @@ namespace {
     /// particular stride.
     std::map<const SCEV *, IVsOfOneStride> IVsByStride;
 
+    /// StrideNoReuse - Keep track of all the strides whose ivs cannot be
+    /// reused (nor should they be rewritten to reuse other strides).
+    SmallSet<const SCEV *, 4> StrideNoReuse;
+
     /// DeadInsts - Keep track of instructions we may have made dead, so that
     /// we can remove them after we are done working.
     SmallVector<WeakVH, 16> DeadInsts;
@@ -99,7 +109,8 @@ namespace {
   public:
     static char ID; // Pass ID, replacement for typeid
     explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
-      LoopPass(&ID), TLI(tli) {}
+      LoopPass(&ID), TLI(tli) {
+    }
 
     bool runOnLoop(Loop *L, LPPassManager &LPM);
 
@@ -107,11 +118,13 @@ namespace {
       // We split critical edges, so we change the CFG.  However, we do update
       // many analyses if they are around.
       AU.addPreservedID(LoopSimplifyID);
-      AU.addPreserved("loops");
-      AU.addPreserved("domfrontier");
-      AU.addPreserved("domtree");
+      AU.addPreserved<LoopInfo>();
+      AU.addPreserved<DominanceFrontier>();
+      AU.addPreserved<DominatorTree>();
 
       AU.addRequiredID(LoopSimplifyID);
+      AU.addRequired<LoopInfo>();
+      AU.addRequired<DominatorTree>();
       AU.addRequired<ScalarEvolution>();
       AU.addPreserved<ScalarEvolution>();
       AU.addRequired<IVUsers>();
@@ -215,17 +228,19 @@ void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
   if (DeadInsts.empty()) return;
 
   while (!DeadInsts.empty()) {
-    Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
+    Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.back());
+    DeadInsts.pop_back();
 
     if (I == 0 || !isInstructionTriviallyDead(I))
       continue;
 
-    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) {
       if (Instruction *U = dyn_cast<Instruction>(*OI)) {
         *OI = 0;
         if (U->use_empty())
           DeadInsts.push_back(U);
       }
+    }
 
     I->eraseFromParent();
     Changed = true;
@@ -285,6 +300,9 @@ namespace {
   /// BasedUser - For a particular base value, keep information about how we've
   /// partitioned the expression so far.
   struct BasedUser {
+    /// SE - The current ScalarEvolution object.
+    ScalarEvolution *SE;
+
     /// Base - The Base value for the PHI node that needs to be inserted for
     /// this use.  As the use is processed, information gets moved from this
     /// field to the Imm field (below).  BasedUser values are sorted by this
@@ -316,9 +334,9 @@ namespace {
     bool isUseOfPostIncrementedValue;
 
     BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
-      : Base(IVSU.getOffset()), Inst(IVSU.getUser()),
+      : SE(se), Base(IVSU.getOffset()), Inst(IVSU.getUser()),
         OperandValToReplace(IVSU.getOperandValToReplace()),
-        Imm(se->getIntegerSCEV(0, Base->getType())),
+        Imm(SE->getIntegerSCEV(0, Base->getType())),
         isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue()) {}
 
     // Once we rewrite the code to insert the new IVs we want, update the
@@ -327,14 +345,14 @@ namespace {
     void RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
                                         Instruction *InsertPt,
                                        SCEVExpander &Rewriter, Loop *L, Pass *P,
-                                        SmallVectorImpl<WeakVH> &DeadInsts,
-                                        ScalarEvolution *SE);
+                                        LoopInfo &LI,
+                                        SmallVectorImpl<WeakVH> &DeadInsts);
 
     Value *InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
                                        const Type *Ty,
                                        SCEVExpander &Rewriter,
-                                       Instruction *IP,
-                                       ScalarEvolution *SE);
+                                       Instruction *IP, Loop *L,
+                                       LoopInfo &LI);
     void dump() const;
   };
 }
@@ -348,12 +366,27 @@ void BasedUser::dump() const {
 Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
                                               const Type *Ty,
                                               SCEVExpander &Rewriter,
-                                              Instruction *IP,
-                                              ScalarEvolution *SE) {
-  Value *Base = Rewriter.expandCodeFor(NewBase, 0, IP);
+                                              Instruction *IP, Loop *L,
+                                              LoopInfo &LI) {
+  // Figure out where we *really* want to insert this code.  In particular, if
+  // the user is inside of a loop that is nested inside of L, we really don't
+  // want to insert this expression before the user, we'd rather pull it out as
+  // many loops as possible.
+  Instruction *BaseInsertPt = IP;
+
+  // Figure out the most-nested loop that IP is in.
+  Loop *InsertLoop = LI.getLoopFor(IP->getParent());
+
+  // If InsertLoop is not L, and InsertLoop is nested inside of L, figure out
+  // the preheader of the outer-most loop where NewBase is not loop invariant.
+  if (L->contains(IP->getParent()))
+    while (InsertLoop && NewBase->isLoopInvariant(InsertLoop)) {
+      BaseInsertPt = InsertLoop->getLoopPreheader()->getTerminator();
+      InsertLoop = InsertLoop->getParentLoop();
+    }
+
+  Value *Base = Rewriter.expandCodeFor(NewBase, 0, BaseInsertPt);
 
-  // Wrap the base in a SCEVUnknown so that ScalarEvolution doesn't try to
-  // re-analyze it.
   const SCEV *NewValSCEV = SE->getUnknown(Base);
 
   // Always emit the immediate into the same block as the user.
@@ -372,8 +405,8 @@ Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *const &NewBase,
 void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
                                                Instruction *NewBasePt,
                                       SCEVExpander &Rewriter, Loop *L, Pass *P,
-                                      SmallVectorImpl<WeakVH> &DeadInsts,
-                                      ScalarEvolution *SE) {
+                                      LoopInfo &LI,
+                                      SmallVectorImpl<WeakVH> &DeadInsts) {
   if (!isa<PHINode>(Inst)) {
     // By default, insert code at the user instruction.
     BasicBlock::iterator InsertPt = Inst;
@@ -402,7 +435,7 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
     }
     Value *NewVal = InsertCodeForBaseAtPosition(NewBase,
                                                 OperandValToReplace->getType(),
-                                                Rewriter, InsertPt, SE);
+                                                Rewriter, InsertPt, L, LI);
     // Replace the use of the operand Value with the new Phi we just created.
     Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
 
@@ -464,7 +497,7 @@ void BasedUser::RewriteInstructionToUseNewBase(const SCEV *const &NewBase,
                                 PHIPred->getTerminator() :
                                 OldLoc->getParent()->getTerminator();
         Code = InsertCodeForBaseAtPosition(NewBase, PN->getType(),
-                                           Rewriter, InsertPt, SE);
+                                           Rewriter, InsertPt, L, LI);
 
         DEBUG(errs() << "      Changing PHI use to ");
         DEBUG(WriteAsOperand(errs(), Code, /*PrintType=*/false));
@@ -940,13 +973,17 @@ const SCEV *LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
                                 const SCEV *const &Stride,
                                 IVExpr &IV, const Type *Ty,
                                 const std::vector<BasedUser>& UsersToProcess) {
+  if (StrideNoReuse.count(Stride))
+    return SE->getIntegerSCEV(0, Stride->getType());
+
   if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
     int64_t SInt = SC->getValue()->getSExtValue();
     for (unsigned NewStride = 0, e = IU->StrideOrder.size();
          NewStride != e; ++NewStride) {
       std::map<const SCEV *, IVsOfOneStride>::iterator SI =
                 IVsByStride.find(IU->StrideOrder[NewStride]);
-      if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
+      if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first) ||
+          StrideNoReuse.count(SI->first))
         continue;
       // The other stride has no uses, don't reuse it.
       std::map<const SCEV *, IVUsersOfOneStride *>::iterator UI =
@@ -1705,8 +1742,8 @@ LoopStrengthReduce::StrengthReduceIVUsersOfStride(const SCEV *const &Stride,
         RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
 
       User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
-                                          Rewriter, L, this,
-                                          DeadInsts, SE);
+                                          Rewriter, L, this, *LI,
+                                          DeadInsts);
 
       // Mark old value we replaced as possibly dead, so that it is eliminated
       // if we just replaced the last use of that value.
@@ -2670,6 +2707,8 @@ bool LoopStrengthReduce::OptimizeLoopCountIV(Loop *L) {
 
 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
   IU = &getAnalysis<IVUsers>();
+  LI = &getAnalysis<LoopInfo>();
+  DT = &getAnalysis<DominatorTree>();
   SE = &getAnalysis<ScalarEvolution>();
   Changed = false;
 
@@ -2715,14 +2754,15 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
     // After all sharing is done, see if we can adjust the loop to test against
     // zero instead of counting up to a maximum.  This is usually faster.
     OptimizeLoopCountIV(L);
+  }
 
-    // We're done analyzing this loop; release all the state we built up for it.
-    IVsByStride.clear();
+  // We're done analyzing this loop; release all the state we built up for it.
+  IVsByStride.clear();
+  StrideNoReuse.clear();
 
-    // Clean up after ourselves
-    if (!DeadInsts.empty())
-      DeleteTriviallyDeadInstructions();
-  }
+  // Clean up after ourselves
+  if (!DeadInsts.empty())
+    DeleteTriviallyDeadInstructions();
 
   // At this point, it is worth checking to see if any recurrence PHIs are also
   // dead, so that we can remove them as well.