[PATCH] Bug 20788 - bugpoint does not respect the "Alias must point to a definition"

[Nick Johnson]

@dberlin: your testcase demonstrates that a GlobalAlias may refer to any kind of ConstantExpr, whereas my previous patch incorrectly assumed that the aliasee must be an llvm::Function.

Consequently, the test on line 194 needs a ->stripPointerCasts().  My latest patch handles that testcase correctly.

@dberlin: you mentioned you have many test cases.  Would you be so kind as to run this latest patch on them?  Thanks,


http://reviews.llvm.org/D9529

Files:
  tools/bugpoint/ExtractFunction.cpp

Index: tools/bugpoint/ExtractFunction.cpp
===================================================================
--- tools/bugpoint/ExtractFunction.cpp
+++ tools/bugpoint/ExtractFunction.cpp
@@ -184,6 +184,26 @@
 // blocks, making it external.
 //
 void llvm::DeleteFunctionBody(Function *F) {
+  // First, check whether a GlobalAlias references this definition.
+  // GlobalAlias MAY NOT reference declarations.
+  for (;;) {
+    // 1. Find aliases
+    SmallVector<GlobalAlias*,1> aliases;
+    Module *M = F->getParent();
+    for (Module::alias_iterator I=M->alias_begin(), E=M->alias_end(); I!=E; ++I)
+      if (I->getAliasee()->stripPointerCasts() == F)
+        aliases.push_back(&*I);
+    if (aliases.empty())
+      break;
+    // 2. Resolve aliases
+    for (unsigned i=0, e=aliases.size(); i<e; ++i) {
+      aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
+      aliases[i]->eraseFromParent();
+    }
+    // 3. Repeat until no more aliases found; there might
+    // be an alias to an alias...
+  }
+
   // delete the body of the function...
   F->deleteBody();
   assert(F->isDeclaration() && "This didn't make the function external!");

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