Rebased PNaCl localmods in LLVM to 223109

lib/Transforms/NaCl/StripMetadata.cpp

+//===- StripMetadata.cpp - Strip non-stable non-debug metadata       ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// The StripMetadata transformation strips instruction attachment
+// metadata, such as !tbaa and !prof metadata.
+// TODO: Strip NamedMetadata too.
+//
+// It does not strip debug metadata.  Debug metadata is used by debug
+// intrinsic functions and calls to those intrinsic functions.  Use the
+// -strip-debug or -strip pass to strip that instead.
+//
+// The goal of this pass is to reduce bitcode ABI surface area.
+// We don't know yet which kind of metadata is considered stable.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/NaCl.h"
+
+using namespace llvm;
+
+namespace {
+  class StripMetadata : public ModulePass {
+  public:
+    static char ID;
+    StripMetadata() : ModulePass(ID), ShouldStripModuleFlags(false) {
+      initializeStripMetadataPass(*PassRegistry::getPassRegistry());
+    }
+
+    virtual bool runOnModule(Module &M);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+    }
+
+  protected:
+    bool ShouldStripModuleFlags;
+  };
+
+  class StripModuleFlags : public StripMetadata {
+  public:
+    static char ID;
+    StripModuleFlags() : StripMetadata() {
+      initializeStripModuleFlagsPass(*PassRegistry::getPassRegistry());
+      ShouldStripModuleFlags = true;
+    }
+  };
+}
+
+char StripMetadata::ID = 0;
+INITIALIZE_PASS(StripMetadata, "strip-metadata",
+                "Strip all non-stable non-debug metadata from a module.",
+                false, false)
+
+char StripModuleFlags::ID = 0;
+INITIALIZE_PASS(StripModuleFlags, "strip-module-flags",
+                "Strip all non-stable non-debug metadata from a module, "
+                "including the llvm.module.flags metadata.",
+                false, false)
+
+ModulePass *llvm::createStripMetadataPass() {
+  return new StripMetadata();
+}
+
+ModulePass *llvm::createStripModuleFlagsPass() {
+  return new StripModuleFlags();
+}
+
+static bool IsWhitelistedMetadata(const NamedMDNode *node,
+                                  bool StripModuleFlags) {
+  // Leave debug metadata to the -strip-debug pass.
+  return (node->getName().startswith("llvm.dbg.") ||
+          // "Debug Info Version" is in llvm.module.flags.
+          (!StripModuleFlags && node->getName().equals("llvm.module.flags")));
+}
+
+static bool DoStripMetadata(Module &M, bool StripModuleFlags) {
+  bool Changed = false;
+
+  if (!StripModuleFlags)
+    for (Function &F : M)
+      for (BasicBlock &B : F)
+        for (Instruction &I : B) {
+          SmallVector<std::pair<unsigned, MDNode *>, 8> InstMeta;
+          // Let the debug metadata be stripped by the -strip-debug pass.
+          I.getAllMetadataOtherThanDebugLoc(InstMeta);
+          for (size_t i = 0; i < InstMeta.size(); ++i) {
+            I.setMetadata(InstMeta[i].first, NULL);
+            Changed = true;
+          }
+        }
+
+  // Strip unsupported named metadata.
+  SmallVector<NamedMDNode*, 8> ToErase;
+  for (Module::NamedMDListType::iterator I = M.named_metadata_begin(),
+           E = M.named_metadata_end(); I != E; ++I) {
+    if (!IsWhitelistedMetadata(I, StripModuleFlags))
+      ToErase.push_back(I);
+  }
+  for (size_t i = 0; i < ToErase.size(); ++i)
+    M.eraseNamedMetadata(ToErase[i]);
+
+  return Changed;
+}
+
+bool StripMetadata::runOnModule(Module &M) {
+  return DoStripMetadata(M, ShouldStripModuleFlags);
+}