[llvm] a1ed025 - Revert "[SCEV] Don't walk uses of phis without SCEV expression when forgetting"

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-04-15T09:43:52+02:00
New Revision: a1ed025d0ef99ba76c30b3d3753e5c2c40f9b755

URL: https://github.com/llvm/llvm-project/commit/a1ed025d0ef99ba76c30b3d3753e5c2c40f9b755
DIFF: https://github.com/llvm/llvm-project/commit/a1ed025d0ef99ba76c30b3d3753e5c2c40f9b755.diff

LOG: Revert "[SCEV] Don't walk uses of phis without SCEV expression when forgetting"

This reverts commit faf9f11589ce892b31d271917cf840f8ca903221.

Issues with this patch have been reported in
https://reviews.llvm.org/D100264#2689917 and
https://bugs.llvm.org/show_bug.cgi?id=49967.

Added: 
    

Modified: 
    llvm/include/llvm/Analysis/ScalarEvolution.h
    llvm/lib/Analysis/ScalarEvolution.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Analysis/ScalarEvolution.h b/llvm/include/llvm/Analysis/ScalarEvolution.h
index 5f06c2926f06d..8407be99a82b1 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolution.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -2053,12 +2053,6 @@ class ScalarEvolution {
   std::tuple<SCEV *, FoldingSetNodeID, void *>
   findExistingSCEVInCache(SCEVTypes SCEVType, ArrayRef<const SCEV *> Ops);
 
-  /// Push PHI nodes in the header of the given loop onto the given Worklist
-  /// if they have a cached SCEV expression. If no expression is cached, then
-  /// there also aren't any dependent expressions to invalidate.
-  void pushCachedLoopPHIs(const Loop *L,
-                          SmallVectorImpl<Instruction *> &Worklist) const;
-
   FoldingSet<SCEV> UniqueSCEVs;
   FoldingSet<SCEVPredicate> UniquePreds;
   BumpPtrAllocator SCEVAllocator;

diff  --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 446e5e3651a78..4630c5562623c 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7020,16 +7020,13 @@ bool ScalarEvolution::isBackedgeTakenCountMaxOrZero(const Loop *L) {
 }
 
 /// Push PHI nodes in the header of the given loop onto the given Worklist.
-/// Only push PHIs for which a SCEV expression has been cached, otherwise there
-/// cannot be any dependent expressions to invalidate.
-void ScalarEvolution::pushCachedLoopPHIs(
-    const Loop *L, SmallVectorImpl<Instruction *> &Worklist) const {
+static void
+PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
   BasicBlock *Header = L->getHeader();
-  for (PHINode &PN : Header->phis()) {
-    auto It = ValueExprMap.find_as(static_cast<Value *>(&PN));
-    if (It != ValueExprMap.end())
-      Worklist.push_back(&PN);
-  }
+
+  // Push all Loop-header PHIs onto the Worklist stack.
+  for (PHINode &PN : Header->phis())
+    Worklist.push_back(&PN);
 }
 
 const ScalarEvolution::BackedgeTakenInfo &
@@ -7090,7 +7087,7 @@ ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
   // it handles SCEVUnknown PHI nodes specially.
   if (Result.hasAnyInfo()) {
     SmallVector<Instruction *, 16> Worklist;
-    pushCachedLoopPHIs(L, Worklist);
+    PushLoopPHIs(L, Worklist);
 
     SmallPtrSet<Instruction *, 8> Discovered;
     while (!Worklist.empty()) {
@@ -7213,7 +7210,7 @@ void ScalarEvolution::forgetLoop(const Loop *L) {
     }
 
     // Drop information about expressions based on loop-header PHIs.
-    pushCachedLoopPHIs(CurrL, Worklist);
+    PushLoopPHIs(CurrL, Worklist);
 
     while (!Worklist.empty()) {
       Instruction *I = Worklist.pop_back_val();