[SandboxVec][Scheduler] Fix clear() to clear all state

[vporpo]

This patch fixes the scheduler's clear() function to also clear the ReadyList. Not doing so is a bug and results in crashes when the ReadyList contains stale instructions, because it was never clered.

[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: vporpo (vporpo)

Changes

This patch fixes the scheduler's clear() function to also clear the ReadyList. Not doing so is a bug and results in crashes when the ReadyList contains stale instructions, because it was never clered.

---

Full diff: https://github.com/llvm/llvm-project/pull/124214.diff

2 Files Affected:

• (modified) llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/DependencyGraph.h (+7)
• (modified) llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Scheduler.h (+3)

diff --git a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/DependencyGraph.h b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/DependencyGraph.h
index 00b53b42e2e572..b2d7c9b8aa8bbc 100644
--- a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/DependencyGraph.h
+++ b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/DependencyGraph.h
@@ -417,6 +417,13 @@ class DependencyGraph {
     DAGInterval = {};
   }
 #ifndef NDEBUG
+  /// \Returns true if the DAG's state is clear. Used in assertions.
+  bool empty() const {
+    bool IsEmpty = InstrToNodeMap.empty();
+    assert(IsEmpty == DAGInterval.empty() &&
+           "Interval and InstrToNodeMap out of sync!");
+    return IsEmpty;
+  }
   void print(raw_ostream &OS) const;
   LLVM_DUMP_METHOD void dump() const;
 #endif // NDEBUG
diff --git a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Scheduler.h b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Scheduler.h
index 52891c3f7535c9..25432e1396c73f 100644
--- a/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Scheduler.h
+++ b/llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/Scheduler.h
@@ -164,7 +164,10 @@ class Scheduler {
     Bndls.clear();
     // TODO: clear view once it lands.
     DAG.clear();
+    ReadyList.clear();
     ScheduleTopItOpt = std::nullopt;
+    assert(Bndls.empty() && DAG.empty() && ReadyList.empty() &&
+           !ScheduleTopItOpt && "Expected empty state!");
   }
 
 #ifndef NDEBUG