From e637ff5e9a884299418c4da192ab88b2d2197f28 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 19 Apr 2010 21:48:58 +0000
Subject: Remove the Expr member from IVUsers. Instead of remembering the
 expression, just ask ScalarEvolution for it on demand. This helps IVUsers be
 more robust in the case of expressions changing underneath it. This fixes
 PR6862.

llvm-svn: 101819
---
 llvm/lib/Analysis/IVUsers.cpp | 56 +++++++++++++++++++++----------------------
 1 file changed, 27 insertions(+), 29 deletions(-)

(limited to 'llvm/lib/Analysis/IVUsers.cpp')

diff --git a/llvm/lib/Analysis/IVUsers.cpp b/llvm/lib/Analysis/IVUsers.cpp
index fbd3e707127..2c997dae585 100644
--- a/llvm/lib/Analysis/IVUsers.cpp
+++ b/llvm/lib/Analysis/IVUsers.cpp
@@ -122,23 +122,21 @@ bool IVUsers::AddUsersIfInteresting(Instruction *I) {
 
     if (AddUserToIVUsers) {
       // Okay, we found a user that we cannot reduce.
-      IVUses.push_back(new IVStrideUse(this, ISE, User, I));
+      IVUses.push_back(new IVStrideUse(this, User, I));
       IVStrideUse &NewUse = IVUses.back();
       // Transform the expression into a normalized form.
-      NewUse.Expr =
-        TransformForPostIncUse(NormalizeAutodetect, NewUse.Expr,
-                               User, I,
-                               NewUse.PostIncLoops,
-                               *SE, *DT);
-      DEBUG(dbgs() << "   NORMALIZED TO: " << *NewUse.Expr << '\n');
+      ISE = TransformForPostIncUse(NormalizeAutodetect,
+                                   ISE, User, I,
+                                   NewUse.PostIncLoops,
+                                   *SE, *DT);
+      DEBUG(dbgs() << "   NORMALIZED TO: " << *ISE << '\n');
     }
   }
   return true;
 }
 
-IVStrideUse &IVUsers::AddUser(const SCEV *Expr,
-                              Instruction *User, Value *Operand) {
-  IVUses.push_back(new IVStrideUse(this, Expr, User, Operand));
+IVStrideUse &IVUsers::AddUser(Instruction *User, Value *Operand) {
+  IVUses.push_back(new IVStrideUse(this, User, Operand));
   return IVUses.back();
 }
 
@@ -169,15 +167,6 @@ bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
   return false;
 }
 
-/// getReplacementExpr - Return a SCEV expression which computes the
-/// value of the OperandValToReplace of the given IVStrideUse.
-const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &U) const {
-  PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(U.PostIncLoops);
-  return TransformForPostIncUse(Denormalize, U.getExpr(),
-                                U.getUser(), U.getOperandValToReplace(),
-                                Loops, *SE, *DT);
-}
-
 void IVUsers::print(raw_ostream &OS, const Module *M) const {
   OS << "IV Users for loop ";
   WriteAsOperand(OS, L->getHeader(), false);
@@ -194,8 +183,7 @@ void IVUsers::print(raw_ostream &OS, const Module *M) const {
        E = IVUses.end(); UI != E; ++UI) {
     OS << "  ";
     WriteAsOperand(OS, UI->getOperandValToReplace(), false);
-    OS << " = "
-       << *getReplacementExpr(*UI);
+    OS << " = " << *getReplacementExpr(*UI);
     for (PostIncLoopSet::const_iterator
          I = UI->PostIncLoops.begin(),
          E = UI->PostIncLoops.end(); I != E; ++I) {
@@ -218,6 +206,21 @@ void IVUsers::releaseMemory() {
   IVUses.clear();
 }
 
+/// getReplacementExpr - Return a SCEV expression which computes the
+/// value of the OperandValToReplace.
+const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &IU) const {
+  return SE->getSCEV(IU.getOperandValToReplace());
+}
+
+/// getExpr - Return the expression for the use.
+const SCEV *IVUsers::getExpr(const IVStrideUse &IU) const {
+  return
+    TransformForPostIncUse(Normalize, getReplacementExpr(IU),
+                           IU.getUser(), IU.getOperandValToReplace(),
+                           const_cast<PostIncLoopSet &>(IU.getPostIncLoops()),
+                           *SE, *DT);
+}
+
 static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
   if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
     if (AR->getLoop() == L)
@@ -236,18 +239,13 @@ static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
   return 0;
 }
 
-const SCEV *IVStrideUse::getStride(const Loop *L) const {
-  if (const SCEVAddRecExpr *AR = findAddRecForLoop(getExpr(), L))
-    return AR->getStepRecurrence(*Parent->SE);
+const SCEV *IVUsers::getStride(const IVStrideUse &IU, const Loop *L) const {
+  if (const SCEVAddRecExpr *AR = findAddRecForLoop(getExpr(IU), L))
+    return AR->getStepRecurrence(*SE);
   return 0;
 }
 
 void IVStrideUse::transformToPostInc(const Loop *L) {
-  PostIncLoopSet Loops;
-  Loops.insert(L);
-  Expr = TransformForPostIncUse(Normalize, Expr,
-                                getUser(), getOperandValToReplace(),
-                                Loops, *Parent->SE, *Parent->DT);
   PostIncLoops.insert(L);
 }
 
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