Revert "[BasicAA] Revert "Revert r218714 - Make better use of zext and sign informati...

[oota-llvm.git] / lib / Analysis / IVUsers.cpp

diff --git a/lib/Analysis/IVUsers.cpp b/lib/Analysis/IVUsers.cpp
index 7eade544578d5be0cbb2d94054ac59e2d2035a6a..12e6cefafd2936fe34529e70ffde72d9dd8737bd 100644 (file)
--- a/lib/Analysis/IVUsers.cpp
+++ b/lib/Analysis/IVUsers.cpp
@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define DEBUG_TYPE "iv-users"
 #include "llvm/Analysis/IVUsers.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Analysis/LoopPass.h"
@@ -29,6 +28,8 @@
 #include <algorithm>
 using namespace llvm;
 
+#define DEBUG_TYPE "iv-users"
+
 char IVUsers::ID = 0;
 INITIALIZE_PASS_BEGIN(IVUsers, "iv-users",
                       "Induction Variable Users", false, true)
@@ -83,8 +84,8 @@ static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
 /// form.
 static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
                                  const LoopInfo *LI,
-                                 SmallPtrSet<Loop*,16> &SimpleLoopNests) {
-  Loop *NearestLoop = 0;
+                                 SmallPtrSetImpl<Loop*> &SimpleLoopNests) {
+  Loop *NearestLoop = nullptr;
   for (DomTreeNode *Rung = DT->getNode(BB);
        Rung; Rung = Rung->getIDom()) {
     BasicBlock *DomBB = Rung->getBlock();
@@ -111,7 +112,7 @@ static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
 /// reducible SCEV, recursively add its users to the IVUsesByStride set and
 /// return true.  Otherwise, return false.
 bool IVUsers::AddUsersImpl(Instruction *I,
-                           SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+                           SmallPtrSetImpl<Loop*> &SimpleLoopNests) {
   // Add this IV user to the Processed set before returning false to ensure that
   // all IV users are members of the set. See IVUsers::isIVUserOrOperand.
   if (!Processed.insert(I))
@@ -185,15 +186,34 @@ bool IVUsers::AddUsersImpl(Instruction *I,
 
     if (AddUserToIVUsers) {
       // Okay, we found a user that we cannot reduce.
-      IVUses.push_back(new IVStrideUse(this, User, I));
-      IVStrideUse &NewUse = IVUses.back();
+      IVStrideUse &NewUse = AddUser(User, I);
       // Autodetect the post-inc loop set, populating NewUse.PostIncLoops.
       // The regular return value here is discarded; instead of recording
       // it, we just recompute it when we need it.
+      const SCEV *OriginalISE = ISE;
       ISE = TransformForPostIncUse(NormalizeAutodetect,
                                    ISE, User, I,
                                    NewUse.PostIncLoops,
                                    *SE, *DT);
+
+      // PostIncNormalization effectively simplifies the expression under
+      // pre-increment assumptions. Those assumptions (no wrapping) might not
+      // hold for the post-inc value. Catch such cases by making sure the
+      // transformation is invertible.
+      if (OriginalISE != ISE) {
+        const SCEV *DenormalizedISE =
+          TransformForPostIncUse(Denormalize, ISE, User, I,
+              NewUse.PostIncLoops, *SE, *DT);
+
+        // If we normalized the expression, but denormalization doesn't give the
+        // original one, discard this user.
+        if (OriginalISE != DenormalizedISE) {
+          DEBUG(dbgs() << "   DISCARDING (NORMALIZATION ISN'T INVERTIBLE): "
+                       << *ISE << '\n');
+          IVUses.pop_back();
+          return false;
+        }
+      }
       DEBUG(if (SE->getSCEV(I) != ISE)
               dbgs() << "   NORMALIZED TO: " << *ISE << '\n');
     }
@@ -234,7 +254,7 @@ bool IVUsers::runOnLoop(Loop *l, LPPassManager &LPM) {
   DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   SE = &getAnalysis<ScalarEvolution>();
   DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
-  DL = DLP ? &DLP->getDataLayout() : 0;
+  DL = DLP ? &DLP->getDataLayout() : nullptr;
 
   // Find all uses of induction variables in this loop, and categorize
   // them by stride.  Start by finding all of the PHI nodes in the header for
@@ -267,7 +287,10 @@ void IVUsers::print(raw_ostream &OS, const Module *M) const {
       OS << ")";
     }
     OS << " in  ";
-    UI->getUser()->print(OS);
+    if (UI->getUser())
+      UI->getUser()->print(OS);
+    else
+      OS << "Printing <null> User";
     OS << '\n';
   }
 }
@@ -310,16 +333,16 @@ static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
          I != E; ++I)
       if (const SCEVAddRecExpr *AR = findAddRecForLoop(*I, L))
         return AR;
-    return 0;
+    return nullptr;
   }
 
-  return 0;
+  return nullptr;
 }
 
 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;
+  return nullptr;
 }
 
 void IVStrideUse::transformToPostInc(const Loop *L) {