[llvm] r309925 - [SCEV] Re-enable "Cache results of computeExitLimit"

Maxim Kazantsev via llvm-commits llvm-commits at lists.llvm.org
Thu Aug 3 20:09:30 PDT 2017


Hi Vitaly,

I'm now updating the test to make the sanitizer happy.

Thanks,
Max

From: Vitaly Buka [mailto:vitalybuka at google.com]
Sent: Friday, August 4, 2017 3:54 AM
To: Maxim Kazantsev <max.kazantsev at azul.com>
Cc: llvm-commits <llvm-commits at lists.llvm.org>
Subject: Re: [llvm] r309925 - [SCEV] Re-enable "Cache results of computeExitLimit"


http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/1960/steps/check-llvm%20asan/logs/stdio



[ RUN      ] ScalarEvolutionsTest.SCEVExitLimitForgetLoop

=================================================================

==9898==ERROR: AddressSanitizer: heap-use-after-free on address 0x60b000012ce8 at pc 0x000000d85a56 bp 0x7ffeaee9b0b0 sp 0x7ffeaee9b0a8

READ of size 8 at 0x60b000012ce8 thread T0

    #0 0xd85a55 in addToList /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/Use.h:149:12

    #1 0xd85a55 in addUse /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/Value.h:432

    #2 0xd85a55 in set /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/Value.h:674

    #3 0xd85a55 in operator= /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/Value.h:678

    #4 0xd85a55 in llvm::BranchInst::BranchInst(llvm::BasicBlock*, llvm::BasicBlock*, llvm::Value*, llvm::Instruction*) /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/lib/IR/Instructions.cpp:1148

    #5 0x726734 in Create /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/Instructions.h:3005:19

    #6 0x726734 in CreateCondBr /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/include/llvm/IR/IRBuilder.h:778

    #7 0x726734 in llvm::(anonymous namespace)::ScalarEvolutionsTest_SCEVExitLimitForgetLoop_Test::TestBody() /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/unittests/Analysis/ScalarEvolutionTest.cpp:1007

    #8 0x1055261 in HandleExceptionsInMethodIfSupported<testing::Test, void> /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/utils/unittest/googletest/src/gtest.cc:2458:12

    #9 0x1055261 in testing::Test::Run() /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/utils/unittest/googletest/src/gtest.cc:2474


On Thu, Aug 3, 2017 at 1:41 AM, Max Kazantsev via llvm-commits <llvm-commits at lists.llvm.org<mailto:llvm-commits at lists.llvm.org>> wrote:
Author: mkazantsev
Date: Thu Aug  3 01:41:30 2017
New Revision: 309925

URL: http://llvm.org/viewvc/llvm-project?rev=309925&view=rev
Log:
[SCEV] Re-enable "Cache results of computeExitLimit"

The patch rL309080 was reverted because it did not clean up the cache on "forgetValue"
method call. This patch re-enables this change, adds the missing check and introduces
two new unit tests that make sure that the cache is cleaned properly.

Differential Revision: https://reviews.llvm.org/D36087

Added:
    llvm/trunk/test/Analysis/ScalarEvolution/cache_loop_exit_limit.ll
Modified:
    llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp
    llvm/trunk/unittests/Analysis/ScalarEvolutionTest.cpp

Modified: llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ScalarEvolution.h?rev=309925&r1=309924&r2=309925&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/ScalarEvolution.h (original)
+++ llvm/trunk/include/llvm/Analysis/ScalarEvolution.h Thu Aug  3 01:41:30 2017
@@ -409,6 +409,32 @@ public:
   }
 };

+struct ExitLimitQuery {
+  ExitLimitQuery(const Loop *L, BasicBlock *ExitingBlock, bool AllowPredicates)
+      : L(L), ExitingBlock(ExitingBlock), AllowPredicates(AllowPredicates) {}
+
+  const Loop *L;
+  BasicBlock *ExitingBlock;
+  bool AllowPredicates;
+};
+
+template <> struct DenseMapInfo<ExitLimitQuery> {
+  static inline ExitLimitQuery getEmptyKey() {
+    return ExitLimitQuery(nullptr, nullptr, true);
+  }
+  static inline ExitLimitQuery getTombstoneKey() {
+    return ExitLimitQuery(nullptr, nullptr, false);
+  }
+  static unsigned getHashValue(ExitLimitQuery Val) {
+    return hash_combine(hash_combine(Val.L, Val.ExitingBlock),
+                        Val.AllowPredicates);
+  }
+  static bool isEqual(ExitLimitQuery LHS, ExitLimitQuery RHS) {
+    return LHS.L == RHS.L && LHS.ExitingBlock == RHS.ExitingBlock &&
+           LHS.AllowPredicates == RHS.AllowPredicates;
+  }
+};
+
 /// The main scalar evolution driver. Because client code (intentionally)
 /// can't do much with the SCEV objects directly, they must ask this class
 /// for services.
@@ -584,6 +610,8 @@ private:
              !isa<SCEVCouldNotCompute>(MaxNotTaken);
     }

+    bool hasOperand(const SCEV *S) const;
+
     /// Test whether this ExitLimit contains all information.
     bool hasFullInfo() const {
       return !isa<SCEVCouldNotCompute>(ExactNotTaken);
@@ -704,6 +732,9 @@ private:
   /// function as they are computed.
   DenseMap<const Loop *, BackedgeTakenInfo> PredicatedBackedgeTakenCounts;

+  // Cache the calculated exit limits for the loops.
+  DenseMap<ExitLimitQuery, ExitLimit> ExitLimits;
+
   /// This map contains entries for all of the PHI instructions that we
   /// attempt to compute constant evolutions for.  This allows us to avoid
   /// potentially expensive recomputation of these properties.  An instruction
@@ -856,6 +887,9 @@ private:
   ExitLimit computeExitLimit(const Loop *L, BasicBlock *ExitingBlock,
                              bool AllowPredicates = false);

+  ExitLimit computeExitLimitImpl(const Loop *L, BasicBlock *ExitingBlock,
+                                 bool AllowPredicates = false);
+
   /// Compute the number of times the backedge of the specified loop will
   /// execute if its exit condition were a conditional branch of ExitCond,
   /// TBB, and FBB.
@@ -1095,8 +1129,9 @@ private:
   /// to be a constant.
   Optional<APInt> computeConstantDifference(const SCEV *LHS, const SCEV *RHS);

-  /// Drop memoized information computed for S.
-  void forgetMemoizedResults(const SCEV *S);
+  /// Drop memoized information computed for S. Only erase Exit Limits info if
+  /// we expect that the operation we have made is going to change it.
+  void forgetMemoizedResults(const SCEV *S, bool EraseExitLimit = true);

   /// Return an existing SCEV for V if there is one, otherwise return nullptr.
   const SCEV *getExistingSCEV(Value *V);

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=309925&r1=309924&r2=309925&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Thu Aug  3 01:41:30 2017
@@ -6200,7 +6200,7 @@ ScalarEvolution::getBackedgeTakenInfo(co
         // own when it gets to that point.
         if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
           eraseValueFromMap(It->first);
-          forgetMemoizedResults(Old);
+          forgetMemoizedResults(Old, false);
         }
         if (PHINode *PN = dyn_cast<PHINode>(I))
           ConstantEvolutionLoopExitValue.erase(PN);
@@ -6264,6 +6264,12 @@ void ScalarEvolution::forgetLoop(const L
     PushDefUseChildren(I, Worklist);
   }

+  for (auto I = ExitLimits.begin(); I != ExitLimits.end(); ++I) {
+    auto &Query = I->first;
+    if (Query.L == L)
+      ExitLimits.erase(I);
+  }
+
   // Forget all contained loops too, to avoid dangling entries in the
   // ValuesAtScopes map.
   for (Loop *I : *L)
@@ -6526,6 +6532,18 @@ ScalarEvolution::computeBackedgeTakenCou
 ScalarEvolution::ExitLimit
 ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock,
                                   bool AllowPredicates) {
+  ExitLimitQuery Query(L, ExitingBlock, AllowPredicates);
+  auto MaybeEL = ExitLimits.find(Query);
+  if (MaybeEL != ExitLimits.end())
+    return MaybeEL->second;
+  ExitLimit EL = computeExitLimitImpl(L, ExitingBlock, AllowPredicates);
+  ExitLimits.insert({Query, EL});
+  return EL;
+}
+
+ScalarEvolution::ExitLimit
+ScalarEvolution::computeExitLimitImpl(const Loop *L, BasicBlock *ExitingBlock,
+                                      bool AllowPredicates) {

   // Okay, we've chosen an exiting block.  See what condition causes us to exit
   // at this block and remember the exit block and whether all other targets
@@ -10408,6 +10426,7 @@ ScalarEvolution::ScalarEvolution(ScalarE
       BackedgeTakenCounts(std::move(Arg.BackedgeTakenCounts)),
       PredicatedBackedgeTakenCounts(
           std::move(Arg.PredicatedBackedgeTakenCounts)),
+      ExitLimits(std::move(Arg.ExitLimits)),
       ConstantEvolutionLoopExitValue(
           std::move(Arg.ConstantEvolutionLoopExitValue)),
       ValuesAtScopes(std::move(Arg.ValuesAtScopes)),
@@ -10810,7 +10829,16 @@ bool ScalarEvolution::hasOperand(const S
   return SCEVExprContains(S, [&](const SCEV *Expr) { return Expr == Op; });
 }

-void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
+bool ScalarEvolution::ExitLimit::hasOperand(const SCEV *S) const {
+  auto IsS = [&](const SCEV *X) { return S == X; };
+  auto ContainsS = [&](const SCEV *X) {
+    return !isa<SCEVCouldNotCompute>(X) && SCEVExprContains(X, IsS);
+  };
+  return ContainsS(ExactNotTaken) || ContainsS(MaxNotTaken);
+}
+
+void
+ScalarEvolution::forgetMemoizedResults(const SCEV *S, bool EraseExitLimit) {
   ValuesAtScopes.erase(S);
   LoopDispositions.erase(S);
   BlockDispositions.erase(S);
@@ -10843,6 +10871,13 @@ void ScalarEvolution::forgetMemoizedResu

   RemoveSCEVFromBackedgeMap(BackedgeTakenCounts);
   RemoveSCEVFromBackedgeMap(PredicatedBackedgeTakenCounts);
+
+  // TODO: There is a suspicion that we only need to do it when there is a
+  // SCEVUnknown somewhere inside S. Need to check this.
+  if (EraseExitLimit)
+    for (auto I = ExitLimits.begin(), E = ExitLimits.end(); I != E; ++I)
+      if (I->second.hasOperand(S))
+        ExitLimits.erase(I);
 }

 void ScalarEvolution::verify() const {

Added: llvm/trunk/test/Analysis/ScalarEvolution/cache_loop_exit_limit.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/cache_loop_exit_limit.ll?rev=309925&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/cache_loop_exit_limit.ll (added)
+++ llvm/trunk/test/Analysis/ScalarEvolution/cache_loop_exit_limit.ll Thu Aug  3 01:41:30 2017
@@ -0,0 +1,253 @@
+; RUN: opt -scalar-evolution-max-arith-depth=4 -scalar-evolution-max-add-rec-size=4 -loop-reduce -S < %s | FileCheck %s
+
+; Check that the test does not hang.
+define void @test_01(i32* nocapture %a) local_unnamed_addr {
+
+; CHECK-LABEL: @test_01(
+
+while.body.outer:
+  %arrayidx2 = getelementptr inbounds i32, i32* %a, i64 96
+  %arrayidx2.promoted50 = load i32, i32* %arrayidx2, align 1
+  %a.promoted = load i32, i32* %a, align 1
+  %add347.peel = xor i32 %arrayidx2.promoted50, -1
+  %tobool48.peel = icmp eq i32 %a.promoted, %add347.peel
+  br i1 %tobool48.peel, label %while.body.preheader, label %while.body4.preheader
+
+while.body.preheader:                             ; preds = %while.body.outer
+  %tobool48 = icmp eq i32 %a.promoted, 1
+  br label %while.body
+
+while.body:                                       ; preds = %while.body.preheader, %while.body
+  br i1 %tobool48, label %while.body, label %while.body4.preheader.loopexit
+
+while.body4.preheader.loopexit:                   ; preds = %while.body
+  br label %while.body4.preheader
+
+while.body4.preheader:                            ; preds = %while.body4.preheader.loopexit, %while.body.outer
+  br label %while.body4
+
+while.body4:                                      ; preds = %while.body4.preheader, %while.end.22
+  %0 = phi i32 [ %mul.22, %while.end.22 ], [ %arrayidx2.promoted50, %while.body4.preheader ]
+  %mul = mul nsw i32 %0, %0
+  br label %while.cond17
+
+while.cond17:                                     ; preds = %while.cond17, %while.body4
+  %add22.sink = phi i32 [ %add22, %while.cond17 ], [ %mul, %while.body4 ]
+  %cmp = icmp slt i32 %add22.sink, 0
+  %add22 = add nsw i32 %add22.sink, 1024
+  br i1 %cmp, label %while.cond17, label %while.end
+
+while.end:                                        ; preds = %while.cond17
+  %mul.1 = mul nsw i32 %add22.sink, %add22.sink
+  br label %while.cond17.1
+
+while.cond17.1:                                   ; preds = %while.cond17.1, %while.end
+  %add22.sink.1 = phi i32 [ %add22.1, %while.cond17.1 ], [ %mul.1, %while.end ]
+  %cmp.1 = icmp slt i32 %add22.sink.1, 0
+  %add22.1 = add nsw i32 %add22.sink.1, 2048
+  br i1 %cmp.1, label %while.cond17.1, label %while.end.1
+
+while.end.1:                                      ; preds = %while.cond17.1
+  %mul.2 = mul nsw i32 %add22.sink.1, %add22.sink.1
+  br label %while.cond17.2
+
+while.cond17.2:                                   ; preds = %while.cond17.2, %while.end.1
+  %add22.sink.2 = phi i32 [ %add22.2, %while.cond17.2 ], [ %mul.2, %while.end.1 ]
+  %cmp.2 = icmp slt i32 %add22.sink.2, 0
+  %add22.2 = add nsw i32 %add22.sink.2, 4096
+  br i1 %cmp.2, label %while.cond17.2, label %while.end.2
+
+while.end.2:                                      ; preds = %while.cond17.2
+  %mul.3 = mul nsw i32 %add22.sink.2, %add22.sink.2
+  br label %while.cond17.3
+
+while.cond17.3:                                   ; preds = %while.cond17.3, %while.end.2
+  %add22.sink.3 = phi i32 [ %add22.3, %while.cond17.3 ], [ %mul.3, %while.end.2 ]
+  %cmp.3 = icmp slt i32 %add22.sink.3, 0
+  %add22.3 = add nsw i32 %add22.sink.3, 8192
+  br i1 %cmp.3, label %while.cond17.3, label %while.end.3
+
+while.end.3:                                      ; preds = %while.cond17.3
+  %mul.4 = mul nsw i32 %add22.sink.3, %add22.sink.3
+  br label %while.cond17.4
+
+while.cond17.4:                                   ; preds = %while.cond17.4, %while.end.3
+  %add22.sink.4 = phi i32 [ %add22.4, %while.cond17.4 ], [ %mul.4, %while.end.3 ]
+  %cmp.4 = icmp slt i32 %add22.sink.4, 0
+  %add22.4 = add nsw i32 %add22.sink.4, 16384
+  br i1 %cmp.4, label %while.cond17.4, label %while.end.4
+
+while.end.4:                                      ; preds = %while.cond17.4
+  %mul.5 = mul nsw i32 %add22.sink.4, %add22.sink.4
+  br label %while.cond17.5
+
+while.cond17.5:                                   ; preds = %while.cond17.5, %while.end.4
+  %add22.sink.5 = phi i32 [ %add22.5, %while.cond17.5 ], [ %mul.5, %while.end.4 ]
+  %cmp.5 = icmp slt i32 %add22.sink.5, 0
+  %add22.5 = add nsw i32 %add22.sink.5, 32768
+  br i1 %cmp.5, label %while.cond17.5, label %while.end.5
+
+while.end.5:                                      ; preds = %while.cond17.5
+  %mul.6 = mul nsw i32 %add22.sink.5, %add22.sink.5
+  br label %while.cond17.6
+
+while.cond17.6:                                   ; preds = %while.cond17.6, %while.end.5
+  %add22.sink.6 = phi i32 [ %add22.6, %while.cond17.6 ], [ %mul.6, %while.end.5 ]
+  %cmp.6 = icmp slt i32 %add22.sink.6, 0
+  %add22.6 = add nsw i32 %add22.sink.6, 65536
+  br i1 %cmp.6, label %while.cond17.6, label %while.end.6
+
+while.end.6:                                      ; preds = %while.cond17.6
+  %mul.7 = mul nsw i32 %add22.sink.6, %add22.sink.6
+  br label %while.cond17.7
+
+while.cond17.7:                                   ; preds = %while.cond17.7, %while.end.6
+  %add22.sink.7 = phi i32 [ %add22.7, %while.cond17.7 ], [ %mul.7, %while.end.6 ]
+  %cmp.7 = icmp slt i32 %add22.sink.7, 0
+  %add22.7 = add nsw i32 %add22.sink.7, 131072
+  br i1 %cmp.7, label %while.cond17.7, label %while.end.7
+
+while.end.7:                                      ; preds = %while.cond17.7
+  %mul.8 = mul nsw i32 %add22.sink.7, %add22.sink.7
+  br label %while.cond17.8
+
+while.cond17.8:                                   ; preds = %while.cond17.8, %while.end.7
+  %add22.sink.8 = phi i32 [ %add22.8, %while.cond17.8 ], [ %mul.8, %while.end.7 ]
+  %cmp.8 = icmp slt i32 %add22.sink.8, 0
+  %add22.8 = add nsw i32 %add22.sink.8, 262144
+  br i1 %cmp.8, label %while.cond17.8, label %while.end.8
+
+while.end.8:                                      ; preds = %while.cond17.8
+  %mul.9 = mul nsw i32 %add22.sink.8, %add22.sink.8
+  br label %while.cond17.9
+
+while.cond17.9:                                   ; preds = %while.cond17.9, %while.end.8
+  %add22.sink.9 = phi i32 [ %add22.9, %while.cond17.9 ], [ %mul.9, %while.end.8 ]
+  %cmp.9 = icmp slt i32 %add22.sink.9, 0
+  %add22.9 = add nsw i32 %add22.sink.9, 524288
+  br i1 %cmp.9, label %while.cond17.9, label %while.end.9
+
+while.end.9:                                      ; preds = %while.cond17.9
+  %mul.10 = mul nsw i32 %add22.sink.9, %add22.sink.9
+  br label %while.cond17.10
+
+while.cond17.10:                                  ; preds = %while.cond17.10, %while.end.9
+  %add22.sink.10 = phi i32 [ %add22.10, %while.cond17.10 ], [ %mul.10, %while.end.9 ]
+  %cmp.10 = icmp slt i32 %add22.sink.10, 0
+  %add22.10 = add nsw i32 %add22.sink.10, 1048576
+  br i1 %cmp.10, label %while.cond17.10, label %while.end.10
+
+while.end.10:                                     ; preds = %while.cond17.10
+  %mul.11 = mul nsw i32 %add22.sink.10, %add22.sink.10
+  br label %while.cond17.11
+
+while.cond17.11:                                  ; preds = %while.cond17.11, %while.end.10
+  %add22.sink.11 = phi i32 [ %add22.11, %while.cond17.11 ], [ %mul.11, %while.end.10 ]
+  %cmp.11 = icmp slt i32 %add22.sink.11, 0
+  %add22.11 = add nsw i32 %add22.sink.11, 2097152
+  br i1 %cmp.11, label %while.cond17.11, label %while.end.11
+
+while.end.11:                                     ; preds = %while.cond17.11
+  %mul.12 = mul nsw i32 %add22.sink.11, %add22.sink.11
+  br label %while.cond17.12
+
+while.cond17.12:                                  ; preds = %while.cond17.12, %while.end.11
+  %add22.sink.12 = phi i32 [ %add22.12, %while.cond17.12 ], [ %mul.12, %while.end.11 ]
+  %cmp.12 = icmp slt i32 %add22.sink.12, 0
+  %add22.12 = add nsw i32 %add22.sink.12, 4194304
+  br i1 %cmp.12, label %while.cond17.12, label %while.end.12
+
+while.end.12:                                     ; preds = %while.cond17.12
+  %mul.13 = mul nsw i32 %add22.sink.12, %add22.sink.12
+  br label %while.cond17.13
+
+while.cond17.13:                                  ; preds = %while.cond17.13, %while.end.12
+  %add22.sink.13 = phi i32 [ %add22.13, %while.cond17.13 ], [ %mul.13, %while.end.12 ]
+  %cmp.13 = icmp slt i32 %add22.sink.13, 0
+  %add22.13 = add nsw i32 %add22.sink.13, 8388608
+  br i1 %cmp.13, label %while.cond17.13, label %while.end.13
+
+while.end.13:                                     ; preds = %while.cond17.13
+  %mul.14 = mul nsw i32 %add22.sink.13, %add22.sink.13
+  br label %while.cond17.14
+
+while.cond17.14:                                  ; preds = %while.cond17.14, %while.end.13
+  %add22.sink.14 = phi i32 [ %add22.14, %while.cond17.14 ], [ %mul.14, %while.end.13 ]
+  %cmp.14 = icmp slt i32 %add22.sink.14, 0
+  %add22.14 = add nsw i32 %add22.sink.14, 16777216
+  br i1 %cmp.14, label %while.cond17.14, label %while.end.14
+
+while.end.14:                                     ; preds = %while.cond17.14
+  %mul.15 = mul nsw i32 %add22.sink.14, %add22.sink.14
+  br label %while.cond17.15
+
+while.cond17.15:                                  ; preds = %while.cond17.15, %while.end.14
+  %add22.sink.15 = phi i32 [ %add22.15, %while.cond17.15 ], [ %mul.15, %while.end.14 ]
+  %cmp.15 = icmp slt i32 %add22.sink.15, 0
+  %add22.15 = add nsw i32 %add22.sink.15, 33554432
+  br i1 %cmp.15, label %while.cond17.15, label %while.end.15
+
+while.end.15:                                     ; preds = %while.cond17.15
+  %mul.16 = mul nsw i32 %add22.sink.15, %add22.sink.15
+  br label %while.cond17.16
+
+while.cond17.16:                                  ; preds = %while.cond17.16, %while.end.15
+  %add22.sink.16 = phi i32 [ %add22.16, %while.cond17.16 ], [ %mul.16, %while.end.15 ]
+  %cmp.16 = icmp slt i32 %add22.sink.16, 0
+  %add22.16 = add nsw i32 %add22.sink.16, 67108864
+  br i1 %cmp.16, label %while.cond17.16, label %while.end.16
+
+while.end.16:                                     ; preds = %while.cond17.16
+  %mul.17 = mul nsw i32 %add22.sink.16, %add22.sink.16
+  br label %while.cond17.17
+
+while.cond17.17:                                  ; preds = %while.cond17.17, %while.end.16
+  %add22.sink.17 = phi i32 [ %add22.17, %while.cond17.17 ], [ %mul.17, %while.end.16 ]
+  %cmp.17 = icmp slt i32 %add22.sink.17, 0
+  %add22.17 = add nsw i32 %add22.sink.17, 134217728
+  br i1 %cmp.17, label %while.cond17.17, label %while.end.17
+
+while.end.17:                                     ; preds = %while.cond17.17
+  %mul.18 = mul nsw i32 %add22.sink.17, %add22.sink.17
+  br label %while.cond17.18
+
+while.cond17.18:                                  ; preds = %while.cond17.18, %while.end.17
+  %add22.sink.18 = phi i32 [ %add22.18, %while.cond17.18 ], [ %mul.18, %while.end.17 ]
+  %cmp.18 = icmp slt i32 %add22.sink.18, 0
+  %add22.18 = add nsw i32 %add22.sink.18, 268435456
+  br i1 %cmp.18, label %while.cond17.18, label %while.end.18
+
+while.end.18:                                     ; preds = %while.cond17.18
+  %mul.19 = mul nsw i32 %add22.sink.18, %add22.sink.18
+  br label %while.cond17.19
+
+while.cond17.19:                                  ; preds = %while.cond17.19, %while.end.18
+  %add22.sink.19 = phi i32 [ %add22.19, %while.cond17.19 ], [ %mul.19, %while.end.18 ]
+  %cmp.19 = icmp slt i32 %add22.sink.19, 0
+  %add22.19 = add nsw i32 %add22.sink.19, 536870912
+  br i1 %cmp.19, label %while.cond17.19, label %while.end.19
+
+while.end.19:                                     ; preds = %while.cond17.19
+  %mul.20 = mul nsw i32 %add22.sink.19, %add22.sink.19
+  br label %while.cond17.20
+
+while.cond17.20:                                  ; preds = %while.cond17.20, %while.end.19
+  %add22.sink.20 = phi i32 [ %add22.20, %while.cond17.20 ], [ %mul.20, %while.end.19 ]
+  %cmp.20 = icmp slt i32 %add22.sink.20, 0
+  %add22.20 = add nsw i32 %add22.sink.20, 1073741824
+  br i1 %cmp.20, label %while.cond17.20, label %while.end.20
+
+while.end.20:                                     ; preds = %while.cond17.20
+  %mul.21 = mul nsw i32 %add22.sink.20, %add22.sink.20
+  br label %while.cond17.21
+
+while.cond17.21:                                  ; preds = %while.cond17.21, %while.end.20
+  %add22.sink.21 = phi i32 [ %add22.21, %while.cond17.21 ], [ %mul.21, %while.end.20 ]
+  %cmp.21 = icmp slt i32 %add22.sink.21, 0
+  %add22.21 = or i32 %add22.sink.21, -2147483648
+  br i1 %cmp.21, label %while.cond17.21, label %while.end.22
+
+while.end.22:                                     ; preds = %while.cond17.21
+  %mul.22 = mul nsw i32 %add22.sink.21, %add22.sink.21
+  br label %while.body4
+}

Modified: llvm/trunk/unittests/Analysis/ScalarEvolutionTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Analysis/ScalarEvolutionTest.cpp?rev=309925&r1=309924&r2=309925&view=diff
==============================================================================
--- llvm/trunk/unittests/Analysis/ScalarEvolutionTest.cpp (original)
+++ llvm/trunk/unittests/Analysis/ScalarEvolutionTest.cpp Thu Aug  3 01:41:30 2017
@@ -930,5 +930,165 @@ TEST_F(ScalarEvolutionsTest, SCEVZeroExt
   EXPECT_FALSE(verifyFunction(*F, &errs()));
 }

+// Make sure that SCEV invalidates exit limits after invalidating the values it
+// depends on when we forget a loop.
+TEST_F(ScalarEvolutionsTest, SCEVExitLimitForgetLoop) {
+  /*
+   * Create the following code:
+   * func(i64 addrspace(10)* %arg)
+   * top:
+   *  br label %L.ph
+   * L.ph:
+   *  br label %L
+   * L:
+   *  %phi = phi i64 [i64 0, %L.ph], [ %add, %L2 ]
+   *  %add = add i64 %phi2, 1
+   *  %cond = icmp slt i64 %add, 1000; then becomes 2000.
+   *  br i1 %cond, label %post, label %L2
+   * post:
+   *  ret void
+   *
+   */
+
+  // Create a module with non-integral pointers in it's datalayout
+  Module NIM("nonintegral", Context);
+  std::string DataLayout = M.getDataLayoutStr();
+  if (!DataLayout.empty())
+    DataLayout += "-";
+  DataLayout += "ni:10";
+  NIM.setDataLayout(DataLayout);
+
+  Type *T_int64 = Type::getInt64Ty(Context);
+  Type *T_pint64 = T_int64->getPointerTo(10);
+
+  FunctionType *FTy =
+      FunctionType::get(Type::getVoidTy(Context), {T_pint64}, false);
+  Function *F = cast<Function>(NIM.getOrInsertFunction("foo", FTy));
+
+  Argument *Arg = &*F->arg_begin();
+
+  BasicBlock *Top = BasicBlock::Create(Context, "top", F);
+  BasicBlock *LPh = BasicBlock::Create(Context, "L.ph", F);
+  BasicBlock *L = BasicBlock::Create(Context, "L", F);
+  BasicBlock *Post = BasicBlock::Create(Context, "post", F);
+
+  IRBuilder<> Builder(Top);
+  Builder.CreateBr(LPh);
+
+  Builder.SetInsertPoint(LPh);
+  Builder.CreateBr(L);
+
+  Builder.SetInsertPoint(L);
+  PHINode *Phi = Builder.CreatePHI(T_int64, 2);
+  auto *Add = cast<Instruction>(
+      Builder.CreateAdd(Phi, ConstantInt::get(T_int64, 1), "add"));
+  auto *Limit = ConstantInt::get(T_int64, 1000);
+  auto *Cond = cast<Instruction>(
+      Builder.CreateICmp(ICmpInst::ICMP_SLT, Add, Limit, "cond"));
+  auto *Br = cast<Instruction>(Builder.CreateCondBr(Cond, L, Post));
+  Phi->addIncoming(ConstantInt::get(T_int64, 0), LPh);
+  Phi->addIncoming(Add, L);
+
+  Builder.SetInsertPoint(Post);
+  Builder.CreateRetVoid();
+
+  ScalarEvolution SE = buildSE(*F);
+  auto *Loop = LI->getLoopFor(L);
+  const SCEV *EC = SE.getBackedgeTakenCount(Loop);
+  EXPECT_FALSE(isa<SCEVCouldNotCompute>(EC));
+
+  SE.forgetLoop(Loop);
+  Br->eraseFromParent();
+  Cond->eraseFromParent();
+
+  Builder.SetInsertPoint(L);
+  Builder.CreateICmp(ICmpInst::ICMP_SLT, Add, ConstantInt::get(T_int64, 2000),
+                     "new.cond");
+  Builder.CreateCondBr(Cond, L, Post);
+  const SCEV *NewEC = SE.getBackedgeTakenCount(Loop);
+  EXPECT_NE(EC, NewEC);
+}
+
+// Make sure that SCEV invalidates exit limits after invalidating the values it
+// depends on when we forget a value.
+TEST_F(ScalarEvolutionsTest, SCEVExitLimitForgetValue) {
+  /*
+   * Create the following code:
+   * func(i64 addrspace(10)* %arg)
+   * top:
+   *  br label %L.ph
+   * L.ph:
+   *  %load = load i64 addrspace(10)* %arg
+   *  br label %L
+   * L:
+   *  %phi = phi i64 [i64 0, %L.ph], [ %add, %L2 ]
+   *  %add = add i64 %phi2, 1
+   *  %cond = icmp slt i64 %add, %load ; then becomes 2000.
+   *  br i1 %cond, label %post, label %L2
+   * post:
+   *  ret void
+   *
+   */
+
+  // Create a module with non-integral pointers in it's datalayout
+  Module NIM("nonintegral", Context);
+  std::string DataLayout = M.getDataLayoutStr();
+  if (!DataLayout.empty())
+    DataLayout += "-";
+  DataLayout += "ni:10";
+  NIM.setDataLayout(DataLayout);
+
+  Type *T_int64 = Type::getInt64Ty(Context);
+  Type *T_pint64 = T_int64->getPointerTo(10);
+
+  FunctionType *FTy =
+      FunctionType::get(Type::getVoidTy(Context), {T_pint64}, false);
+  Function *F = cast<Function>(NIM.getOrInsertFunction("foo", FTy));
+
+  Argument *Arg = &*F->arg_begin();
+
+  BasicBlock *Top = BasicBlock::Create(Context, "top", F);
+  BasicBlock *LPh = BasicBlock::Create(Context, "L.ph", F);
+  BasicBlock *L = BasicBlock::Create(Context, "L", F);
+  BasicBlock *Post = BasicBlock::Create(Context, "post", F);
+
+  IRBuilder<> Builder(Top);
+  Builder.CreateBr(LPh);
+
+  Builder.SetInsertPoint(LPh);
+  auto *Load = cast<Instruction>(Builder.CreateLoad(T_int64, Arg, "load"));
+  Builder.CreateBr(L);
+
+  Builder.SetInsertPoint(L);
+  PHINode *Phi = Builder.CreatePHI(T_int64, 2);
+  auto *Add = cast<Instruction>(
+      Builder.CreateAdd(Phi, ConstantInt::get(T_int64, 1), "add"));
+  auto *Cond = cast<Instruction>(
+      Builder.CreateICmp(ICmpInst::ICMP_SLT, Add, Load, "cond"));
+  auto *Br = cast<Instruction>(Builder.CreateCondBr(Cond, L, Post));
+  Phi->addIncoming(ConstantInt::get(T_int64, 0), LPh);
+  Phi->addIncoming(Add, L);
+
+  Builder.SetInsertPoint(Post);
+  Builder.CreateRetVoid();
+
+  ScalarEvolution SE = buildSE(*F);
+  auto *Loop = LI->getLoopFor(L);
+  const SCEV *EC = SE.getBackedgeTakenCount(Loop);
+  EXPECT_FALSE(isa<SCEVCouldNotCompute>(EC));
+
+  SE.forgetValue(Load);
+  Br->eraseFromParent();
+  Cond->eraseFromParent();
+  Load->eraseFromParent();
+
+  Builder.SetInsertPoint(L);
+  Builder.CreateICmp(ICmpInst::ICMP_SLT, Add, ConstantInt::get(T_int64, 2000),
+                     "new.cond");
+  Builder.CreateCondBr(Cond, L, Post);
+  const SCEV *NewEC = SE.getBackedgeTakenCount(Loop);
+  EXPECT_NE(EC, NewEC);
+}
+
 }  // end anonymous namespace
 }  // end namespace llvm


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