[llvm] [LV] Invalidate disposition of SCEV values after loop vectorization (PR #69230)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw created https://github.com/llvm/llvm-project/pull/69230

This PR fixes the assertion failure of `SE.Verify()` after loop vectorization. I found this problem when investigating #69097.

>From 14aff24488bb99314410e17bd45a4188e4c9d100 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 17 Oct 2023 01:21:12 +0800
Subject: [PATCH 1/2] [LV] Add pre-commit tests for PR69097.

---
 .../Transforms/Vectorize/LoopVectorize.cpp    |  5 +++--
 .../LoopVectorize/scev-invalidation.ll        | 22 +++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/Transforms/LoopVectorize/scev-invalidation.ll

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 2ca7e75f97f0f02..f62942b4a200c01 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -10389,8 +10389,9 @@ PreservedAnalyses LoopVectorizePass::run(Function &F,
       PA.preserve<DominatorTreeAnalysis>();
       PA.preserve<ScalarEvolutionAnalysis>();
 
-#ifdef EXPENSIVE_CHECKS
-      SE.verify();
+#ifndef NDEBUG
+      if (VerifySCEV)
+        SE.verify();
 #endif
     }
 
diff --git a/llvm/test/Transforms/LoopVectorize/scev-invalidation.ll b/llvm/test/Transforms/LoopVectorize/scev-invalidation.ll
new file mode 100644
index 000000000000000..08163293c14e85e
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/scev-invalidation.ll
@@ -0,0 +1,22 @@
+; RUN: opt < %s -passes="require<scalar-evolution>,print<scalar-evolution>,loop-vectorize" --verify-scev -force-vector-interleave=2 -force-vector-width=8 -S | FileCheck %s
+
+; CHECK-LABEL: @main(
+; CHECK: vector.body
+define i32 @main(i32 %.pre) {
+entry:
+  br label %for.body
+
+for.body:
+  %g.019 = phi i16 [ 0, %entry ], [ %dec7, %for.body ]
+  %and = and i32 %.pre, 40
+  %0 = sub i32 0, %and
+  %dec7 = add i16 %g.019, 1
+  %cmp.not = icmp eq i16 %dec7, 0
+  br i1 %cmp.not, label %for.inc16, label %for.body
+
+for.inc16:
+  %1 = phi i32 [ %inc, %for.inc16 ], [ 0, %for.body ]
+  %inc = add i32 %1, 1
+  %add12 = add i32 %0, %1
+  br label %for.inc16
+}

>From 4ee333fd252247089d1e02f8eef30ad5374b2519 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 17 Oct 2023 01:35:36 +0800
Subject: [PATCH 2/2] [LV] Invalidate disposition of SCEV values after loop
 vectorization.

---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index f62942b4a200c01..685c561fc4d2e1b 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3543,6 +3543,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State,
 
   // Forget the original basic block.
   PSE.getSE()->forgetLoop(OrigLoop);
+  PSE.getSE()->forgetBlockAndLoopDispositions();
 
   // After vectorization, the exit blocks of the original loop will have
   // additional predecessors. Invalidate SCEVs for the exit phis in case SE