[SCEV] Verify contents of loop disposition cache

It seems that it is sometimes broken. Initial motivation for this was
investigation of https://github.com/llvm/llvm-project/issues/56260, but
it also seems that we have found an unrelated bug in LoopFusion that leaves
broken caches.

Differential Revision: https://reviews.llvm.org/D134158
Reviewed By: nikic

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -13968,6 +13968,24 @@ void ScalarEvolution::verify() const {
   };
   VerifyBECountUsers(/* Predicated */ false);
   VerifyBECountUsers(/* Predicated */ true);
+
+  // Verify intergity of loop disposition cache.
+  for (const auto &It : LoopDispositions) {
+    const SCEV *S = It.first;
+    auto &Values = It.second;
+    for (auto &V : Values) {
+      auto CachedDisposition = V.getInt();
+      const auto *Loop = V.getPointer();
+      const auto RecomputedDisposition = SE2.getLoopDisposition(S, Loop);
+      if (CachedDisposition != RecomputedDisposition) {
+        dbgs() << "Cached disposition of " << *S << " for loop " << *Loop
+               << " is incorrect: cached "
+               << loopDispositionToStr(CachedDisposition) << ", actual "
+               << loopDispositionToStr(RecomputedDisposition) << "\n";
+        std::abort();
+      }
+    }
+  }
 }
 
 bool ScalarEvolution::invalidate(

llvm/test/Transforms/LoopFusion/double_loop_nest_inner_guard.ll

@@ -1,4 +1,7 @@
 ; RUN: opt -S -loop-fusion < %s 2>&1 | FileCheck %s
+; XFAIL: *
+; REQUIRES: asserts
+; Fails due to incorrect cached loop disposition.
 
 ; Verify that LoopFusion can fuse two double-loop nests with guarded inner
 ; loops. Loops are in canonical form.

llvm/test/Transforms/LoopFusion/loop_nest.ll

@@ -1,4 +1,7 @@
 ; RUN: opt -S -loop-fusion < %s | FileCheck %s
+; XFAIL: *
+; REQUIRES: asserts
+; Fails due to incorrect cached loop disposition.
 ;
 ;    int A[1024][1024];
 ;    int B[1024][1024];

llvm/test/Transforms/LoopFusion/triple_loop_nest_inner_guard.ll

@@ -1,4 +1,7 @@
 ; RUN: opt -S -loop-fusion < %s 2>&1 | FileCheck %s
+; XFAIL: *
+; REQUIRES: asserts
+; Fails due to incorrect cached loop disposition.
 
 ; Verify that LoopFusion can fuse two triple-loop nests with guarded inner
 ; loops. Loops are in canonical form.