[llvm] r370014 - [Attributor] Introduce an API to delete stuff

[Johannes Doerfert via llvm-commits]

Author: jdoerfert
Date: Mon Aug 26 21:57:54 2019
New Revision: 370014

URL: http://llvm.org/viewvc/llvm-project?rev=370014&view=rev
Log:
[Attributor] Introduce an API to delete stuff

Summary:
During the fixpoint iteration, including the manifest stage, we should
not delete stuff as other abstract attributes might have a reference to
the value. Through the API this can now be done safely at the very end.

Reviewers: uenoku, sstefan1

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66779

Modified:
    llvm/trunk/include/llvm/Transforms/IPO/Attributor.h
    llvm/trunk/lib/Transforms/IPO/Attributor.cpp

Modified: llvm/trunk/include/llvm/Transforms/IPO/Attributor.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/IPO/Attributor.h?rev=370014&r1=370013&r2=370014&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/IPO/Attributor.h (original)
+++ llvm/trunk/include/llvm/Transforms/IPO/Attributor.h Mon Aug 26 21:57:54 2019
@@ -675,6 +675,15 @@ struct Attributor {
   void identifyDefaultAbstractAttributes(
       Function &F, DenseSet<const char *> *Whitelist = nullptr);
 
+  /// Record that \p I is deleted after information was manifested.
+  void deleteAfterManifest(Instruction &I) { ToBeDeletedInsts.insert(&I); }
+
+  /// Record that \p BB is deleted after information was manifested.
+  void deleteAfterManifest(BasicBlock &BB) { ToBeDeletedBlocks.insert(&BB); }
+
+  /// Record that \p F is deleted after information was manifested.
+  void deleteAfterManifest(Function &F) { ToBeDeletedFunctions.insert(&F); }
+
   /// Return true if \p AA (or its context instruction) is assumed dead.
   ///
   /// If \p LivenessAA is not provided it is queried.
@@ -765,6 +774,14 @@ private:
 
   /// The information cache that holds pre-processed (LLVM-IR) information.
   InformationCache &InfoCache;
+
+  /// Functions, blocks, and instructions we delete after manifest is done.
+  ///
+  ///{
+  SmallPtrSet<Function *, 8> ToBeDeletedFunctions;
+  SmallPtrSet<BasicBlock *, 8> ToBeDeletedBlocks;
+  SmallPtrSet<Instruction *, 8> ToBeDeletedInsts;
+  ///}
 };
 
 /// An interface to query the internal state of an abstract attribute.

Modified: llvm/trunk/lib/Transforms/IPO/Attributor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/Attributor.cpp?rev=370014&r1=370013&r2=370014&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/Attributor.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/Attributor.cpp Mon Aug 26 21:57:54 2019
@@ -2641,6 +2641,26 @@ ChangeStatus Attributor::run() {
   assert(
       NumFinalAAs == AllAbstractAttributes.size() &&
       "Expected the final number of abstract attributes to remain unchanged!");
+
+  // Delete stuff at the end to avoid invalid references and a nice order.
+  LLVM_DEBUG(dbgs() << "\n[Attributor] Delete " << ToBeDeletedFunctions.size()
+                    << " functions and " << ToBeDeletedBlocks.size()
+                    << " blocks and " << ToBeDeletedInsts.size()
+                    << " instructions\n");
+  for (Instruction *I : ToBeDeletedInsts) {
+    if (I->hasNUsesOrMore(1))
+      I->replaceAllUsesWith(UndefValue::get(I->getType()));
+    I->eraseFromParent();
+  }
+  for (BasicBlock *BB : ToBeDeletedBlocks) {
+    // TODO: Check if we need to replace users (PHIs, indirect branches?)
+    BB->eraseFromParent();
+  }
+  for (Function *Fn : ToBeDeletedFunctions) {
+    Fn->replaceAllUsesWith(UndefValue::get(Fn->getType()));
+    Fn->eraseFromParent();
+  }
+
   return ManifestChange;
 }