Remove NormalizeAutodetect; NFC

It is cleaner to have a callback based system where the logic of
whether an add recurrence is normalized or not lives on IVUsers.

This is one step in a multi-step cleanup.

llvm-svn: 300330

1 files changed, 23 insertions, 108 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp b/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
index 17d4c01..becc4bb 100644
--- a/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
@@ -12,88 +12,41 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/IR/Dominators.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
 using namespace llvm;
 
-/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
-/// and now we need to decide whether the user should use the preinc or post-inc
-/// value.  If this user should use the post-inc version of the IV, return true.
-///
-/// Choosing wrong here can break dominance properties (if we choose to use the
-/// post-inc value when we cannot) or it can end up adding extra live-ranges to
-/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
-/// should use the post-inc value).
-static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
-                                       const Loop *L, DominatorTree *DT) {
-  // If the user is in the loop, use the preinc value.
-  if (L->contains(User)) return false;
-
-  BasicBlock *LatchBlock = L->getLoopLatch();
-  if (!LatchBlock)
-    return false;
-
-  // Ok, the user is outside of the loop.  If it is dominated by the latch
-  // block, use the post-inc value.
-  if (DT->dominates(LatchBlock, User->getParent()))
-    return true;
-
-  // There is one case we have to be careful of: PHI nodes.  These little guys
-  // can live in blocks that are not dominated by the latch block, but (since
-  // their uses occur in the predecessor block, not the block the PHI lives in)
-  // should still use the post-inc value.  Check for this case now.
-  PHINode *PN = dyn_cast<PHINode>(User);
-  if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
-
-  // Look at all of the uses of Operand by the PHI node.  If any use corresponds
-  // to a block that is not dominated by the latch block, give up and use the
-  // preincremented value.
-  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
-    if (PN->getIncomingValue(i) == Operand &&
-        !DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
-      return false;
-
-  // Okay, all uses of Operand by PN are in predecessor blocks that really are
-  // dominated by the latch block.  Use the post-incremented value.
-  return true;
-}
-
 namespace {
 
 /// Hold the state used during post-inc expression transformation, including a
 /// map of transformed expressions.
 class PostIncTransform {
   TransformKind Kind;
+  Optional<NormalizePredTy> Pred;
   PostIncLoopSet &Loops;
   ScalarEvolution &SE;
-  DominatorTree &DT;
 
   DenseMap<const SCEV*, const SCEV*> Transformed;
 
 public:
-  PostIncTransform(TransformKind kind, PostIncLoopSet &loops,
-                   ScalarEvolution &se, DominatorTree &dt):
-    Kind(kind), Loops(loops), SE(se), DT(dt) {}
+  PostIncTransform(TransformKind kind, Optional<NormalizePredTy> Pred,
+                   PostIncLoopSet &loops, ScalarEvolution &se)
+      : Kind(kind), Pred(Pred), Loops(loops), SE(se) {}
 
-  const SCEV *TransformSubExpr(const SCEV *S, Instruction *User,
-                               Value *OperandValToReplace);
+  const SCEV *TransformSubExpr(const SCEV *S);
 
 protected:
-  const SCEV *TransformImpl(const SCEV *S, Instruction *User,
-                            Value *OperandValToReplace);
+  const SCEV *TransformImpl(const SCEV *S);
 };
 
 } // namespace
 
 /// Implement post-inc transformation for all valid expression types.
-const SCEV *PostIncTransform::
-TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
+const SCEV *PostIncTransform::TransformImpl(const SCEV *S) {
   if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
     const SCEV *O = X->getOperand();
-    const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
+    const SCEV *N = TransformSubExpr(O);
     if (O != N)
       switch (S->getSCEVType()) {
       case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
@@ -108,44 +61,13 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
     // An addrec. This is the interesting part.
     SmallVector<const SCEV *, 8> Operands;
     const Loop *L = AR->getLoop();
-    // The addrec conceptually uses its operands at loop entry.
-    Instruction *LUser = &L->getHeader()->front();
 
-    transform(
-        AR->operands(), std::back_inserter(Operands),
-        [&](const SCEV *Op) { return TransformSubExpr(Op, LUser, nullptr); });
+    transform(AR->operands(), std::back_inserter(Operands),
+              [&](const SCEV *Op) { return TransformSubExpr(Op); });
 
     // Conservatively use AnyWrap until/unless we need FlagNW.
     const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
     switch (Kind) {
-    case NormalizeAutodetect:
-      // Normalize this SCEV by subtracting the expression for the final step.
-      // We only allow affine AddRecs to be normalized, otherwise we would not
-      // be able to correctly denormalize.
-      // e.g. {1,+,3,+,2} == {-2,+,1,+,2} + {3,+,2}
-      // Normalized form:   {-2,+,1,+,2}
-      // Denormalized form: {1,+,3,+,2}
-      //
-      // However, denormalization would use a different step expression than
-      // normalization (see getPostIncExpr), generating the wrong final
-      // expression: {-2,+,1,+,2} + {1,+,2} => {-1,+,3,+,2}
-      if (AR->isAffine() &&
-          IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
-        const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
-        Result = SE.getMinusSCEV(Result, TransformedStep);
-        Loops.insert(L);
-      }
-#if 0
-      // This assert is conceptually correct, but ScalarEvolution currently
-      // sometimes fails to canonicalize two equal SCEVs to exactly the same
-      // form. It's possibly a pessimization when this happens, but it isn't a
-      // correctness problem, so disable this assert for now.
-      assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
-             "SCEV normalization is not invertible!");
-#endif
-      break;
     case Normalize:
       // We want to normalize step expression, because otherwise we might not be
       // able to denormalize to the original expression.
@@ -161,10 +83,9 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
       //     (100 /u {1,+,1}<%bb16>)}<%bb25>
       //  Note that the initial value changes after normalization +
       //  denormalization, which isn't correct.
-      if (Loops.count(L)) {
+      if ((Pred && (*Pred)(AR)) || (!Pred && Loops.count(L))) {
         const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
+            TransformSubExpr(AR->getStepRecurrence(SE));
         Result = SE.getMinusSCEV(Result, TransformedStep);
       }
 #if 0
@@ -178,8 +99,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
       // stated above.
       if (Loops.count(L)) {
         const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
+            TransformSubExpr(AR->getStepRecurrence(SE));
         Result = SE.getAddExpr(Result, TransformedStep);
       }
       break;
@@ -194,7 +114,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
     for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
          I != E; ++I) {
       const SCEV *O = *I;
-      const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
+      const SCEV *N = TransformSubExpr(O);
       Changed |= N != O;
       Operands.push_back(N);
     }
@@ -213,8 +133,8 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
   if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
     const SCEV *LO = X->getLHS();
     const SCEV *RO = X->getRHS();
-    const SCEV *LN = TransformSubExpr(LO, User, OperandValToReplace);
-    const SCEV *RN = TransformSubExpr(RO, User, OperandValToReplace);
+    const SCEV *LN = TransformSubExpr(LO);
+    const SCEV *RN = TransformSubExpr(RO);
     if (LO != LN || RO != RN)
       return SE.getUDivExpr(LN, RN);
     return S;
@@ -225,9 +145,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
 
 /// Manage recursive transformation across an expression DAG. Revisiting
 /// expressions would lead to exponential recursion.
-const SCEV *PostIncTransform::
-TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
+const SCEV *PostIncTransform::TransformSubExpr(const SCEV *S) {
   if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
     return S;
 
@@ -235,20 +153,17 @@ TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
   if (Result)
     return Result;
 
-  Result = TransformImpl(S, User, OperandValToReplace);
+  Result = TransformImpl(S);
   Transformed[S] = Result;
   return Result;
 }
 
 /// Top level driver for transforming an expression DAG into its requested
 /// post-inc form (either "Normalized" or "Denormalized").
-const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
-                                         const SCEV *S,
-                                         Instruction *User,
-                                         Value *OperandValToReplace,
+const SCEV *llvm::TransformForPostIncUse(TransformKind Kind, const SCEV *S,
+                                         Optional<NormalizePredTy> Pred,
                                          PostIncLoopSet &Loops,
-                                         ScalarEvolution &SE,
-                                         DominatorTree &DT) {
-  PostIncTransform Transform(Kind, Loops, SE, DT);
-  return Transform.TransformSubExpr(S, User, OperandValToReplace);
+                                         ScalarEvolution &SE) {
+  PostIncTransform Transform(Kind, Pred, Loops, SE);
+  return Transform.TransformSubExpr(S);
 }