[llvm] a564048 - [SCEV] Properly clean up duplicated FoldCacheUser ID entries.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-12-28T00:09:52Z
New Revision: a564048899a1a1de526a02cfd1a5d691ec31bafd

URL: https://github.com/llvm/llvm-project/commit/a564048899a1a1de526a02cfd1a5d691ec31bafd
DIFF: https://github.com/llvm/llvm-project/commit/a564048899a1a1de526a02cfd1a5d691ec31bafd.diff

LOG: [SCEV] Properly clean up duplicated FoldCacheUser ID entries.

The current code did not properly handled duplicated FoldCacheUser ID
entries when overwriting an existing entry in the FoldCache.

This triggered verification failures reported by @uabelho and #59721.

The patch fixes that by removing stale IDs when overwriting an existing
entry in the cache.

Fixes #59721.

Added: 
    

Modified: 
    llvm/lib/Analysis/ScalarEvolution.cpp
    llvm/test/Analysis/IVUsers/zext-fold-cache-invalidation.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 34a9cddcb08bd..ecf65b4021c00 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -1624,6 +1624,29 @@ static APInt extractConstantWithoutWrapping(ScalarEvolution &SE,
   return APInt(BitWidth, 0);
 }
 
+static void insertFoldCacheEntry(
+    const ScalarEvolution::FoldID &ID, const SCEV *S,
+    DenseMap<ScalarEvolution::FoldID, const SCEV *> &FoldCache,
+    DenseMap<const SCEV *, SmallVector<ScalarEvolution::FoldID, 2>>
+        &FoldCacheUser) {
+  auto I = FoldCache.insert({ID, S});
+  if (!I.second) {
+    // Remove FoldCacheUser entry for ID when replacing an existing FoldCache
+    // entry.
+    auto &UserIDs = FoldCacheUser[I.first->second];
+    assert(count(UserIDs, ID) == 1 && "unexpected duplicates in UserIDs");
+    for (unsigned I = 0; I != UserIDs.size(); ++I)
+      if (UserIDs[I] == ID) {
+        std::swap(UserIDs[I], UserIDs.back());
+        break;
+      }
+    UserIDs.pop_back();
+    I.first->second = S;
+  }
+  auto R = FoldCacheUser.insert({S, {}});
+  R.first->second.push_back(ID);
+}
+
 const SCEV *
 ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
   assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&
@@ -1642,11 +1665,8 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
     return Iter->second;
 
   const SCEV *S = getZeroExtendExprImpl(Op, Ty, Depth);
-  if (!isa<SCEVZeroExtendExpr>(S)) {
-    FoldCache.insert({ID, S});
-    auto R = FoldCacheUser.insert({S, {}});
-    R.first->second.push_back(ID);
-  }
+  if (!isa<SCEVZeroExtendExpr>(S))
+    insertFoldCacheEntry(ID, S, FoldCache, FoldCacheUser);
   return S;
 }
 
@@ -1968,11 +1988,8 @@ ScalarEvolution::getSignExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
     return Iter->second;
 
   const SCEV *S = getSignExtendExprImpl(Op, Ty, Depth);
-  if (!isa<SCEVSignExtendExpr>(S)) {
-    FoldCache.insert({ID, S});
-    auto R = FoldCacheUser.insert({S, {}});
-    R.first->second.push_back(ID);
-  }
+  if (!isa<SCEVSignExtendExpr>(S))
+    insertFoldCacheEntry(ID, S, FoldCache, FoldCacheUser);
   return S;
 }
 

diff  --git a/llvm/test/Analysis/IVUsers/zext-fold-cache-invalidation.ll b/llvm/test/Analysis/IVUsers/zext-fold-cache-invalidation.ll
index 4e71f8cf358fe..38bae6c88d69c 100644
--- a/llvm/test/Analysis/IVUsers/zext-fold-cache-invalidation.ll
+++ b/llvm/test/Analysis/IVUsers/zext-fold-cache-invalidation.ll
@@ -1,10 +1,11 @@
-; RUN: opt -verify-scev -passes='print<iv-users>' -disable-output %s | FileCheck %s
-
-; XFAIL: *
+; RUN: opt -verify-scev -passes='print<iv-users>' -disable-output %s 2>&1 | FileCheck %s
 
 target datalayout = "n16"
 
 define i16 @zext_cache_invalidation_1(i1 %c) {
+; CHECK:      IV Users for loop %loop with backedge-taken count 13:
+; CHECK-NEXT:   %iv = {-3,+,4}<nuw><nsw><%loop> in    %iv.ext = zext i16 %iv to i32
+;
 entry:
   br i1 false, label %loop, label %exit