[SandboxVectorizer] Register erase callback for seed collection (llvm#115951)

Author: Sterling-Augustine

llvm/include/llvm/Transforms/Vectorize/SandboxVectorizer/SeedCollector.h

@@ -223,6 +223,10 @@ class SeedContainer {
     /// Note that the bundles themselves may have additional ordering, created
     /// by the subclasses by insertAt. The bundles themselves may also have used
     /// instructions.
+
+    // TODO: Range_size counts fully used-bundles. Further, iterating over
+    // anything other than the Bundles in a SeedContainer includes used
+    // seeds. Rework the iterator logic to clean this up.
     iterator(BundleMapT &Map, BundleMapT::iterator MapIt, ValT *Vec, int VecIdx)
         : Map(&Map), MapIt(MapIt), Vec(Vec), VecIdx(VecIdx) {}
     value_type &operator*() {
@@ -288,7 +292,7 @@ class SeedCollector {
   SeedContainer StoreSeeds;
   SeedContainer LoadSeeds;
   Context &Ctx;
-
+  Context::CallbackID EraseCallbackID;
   /// \Returns the number of SeedBundle groups for all seed types.
   /// This is to be used for limiting compilation time.
   unsigned totalNumSeedGroups() const {

llvm/lib/Transforms/Vectorize/SandboxVectorizer/SeedCollector.cpp

@@ -159,13 +159,19 @@ template bool isValidMemSeed<StoreInst>(StoreInst *LSI);
 
 SeedCollector::SeedCollector(BasicBlock *BB, ScalarEvolution &SE)
     : StoreSeeds(SE), LoadSeeds(SE), Ctx(BB->getContext()) {
-  // TODO: Register a callback for updating the Collector data structures upon
-  // instr removal
 
   bool CollectStores = CollectSeeds.find(StoreSeedsDef) != std::string::npos;
   bool CollectLoads = CollectSeeds.find(LoadSeedsDef) != std::string::npos;
   if (!CollectStores && !CollectLoads)
     return;
+
+  EraseCallbackID = Ctx.registerEraseInstrCallback([this](Instruction *I) {
+    if (auto SI = dyn_cast<StoreInst>(I))
+      StoreSeeds.erase(SI);
+    else if (auto LI = dyn_cast<LoadInst>(I))
+      LoadSeeds.erase(LI);
+  });
+
   // Actually collect the seeds.
   for (auto &I : *BB) {
     if (StoreInst *SI = dyn_cast<StoreInst>(&I))
@@ -181,8 +187,7 @@ SeedCollector::SeedCollector(BasicBlock *BB, ScalarEvolution &SE)
 }
 
 SeedCollector::~SeedCollector() {
-  // TODO: Unregister the callback for updating the seed datastructures upon
-  // instr removal
+  Ctx.unregisterEraseInstrCallback(EraseCallbackID);
 }
 
 #ifndef NDEBUG

llvm/unittests/Transforms/Vectorize/SandboxVectorizer/SeedCollectorTest.cpp

@@ -374,6 +374,22 @@ define void @foo(ptr noalias %ptr, float %val) {
   // Expect just one vector of store seeds
   EXPECT_EQ(range_size(StoreSeedsRange), 1u);
   ExpectThatElementsAre(SB, {St0, St1, St2, St3});
+  // Check that the EraseInstr callback works.
+
+  // TODO: Range_size counts fully used-bundles even though the iterator skips
+  // them. Further, iterating over anything other than the Bundles in a
+  // SeedContainer includes used seeds. So for now just check that removing all
+  // the seeds from a bundle also empties the bundle.
+  St0->eraseFromParent();
+  St1->eraseFromParent();
+  St2->eraseFromParent();
+  St3->eraseFromParent();
+  size_t nonEmptyBundleCount = 0;
+  for (auto &B : SC.getStoreSeeds()) {
+    (void)B;
+    nonEmptyBundleCount++;
+  }
+  EXPECT_EQ(nonEmptyBundleCount, 0u);
 }
 
 TEST_F(SeedBundleTest, VectorStores) {