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//===- 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;
explicit StripMetadata() : ModulePass(ID) {
initializeStripMetadataPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
}
};
}
char StripMetadata::ID = 0;
INITIALIZE_PASS(StripMetadata, "strip-metadata",
"Strip all non-stable non-debug metadata from a module.",
false, false)
ModulePass *llvm::createStripMetadataPass() {
return new StripMetadata();
}
static bool IsWhitelistedMetadata(const NamedMDNode *node) {
// Leave debug metadata to the -strip-debug pass.
return node->getName().startswith("llvm.dbg.");
}
static bool DoStripMetadata(Module &M) {
bool Changed = false;
for (Module::iterator MI = M.begin(), ME = M.end(); MI != ME; ++MI) {
for (Function::iterator FI = MI->begin(), FE = MI->end(); FI != FE; ++FI) {
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE;
++BI) {
SmallVector<std::pair<unsigned, MDNode *>, 8> InstMeta;
// Let the debug metadata be stripped by the -strip-debug pass.
BI->getAllMetadataOtherThanDebugLoc(InstMeta);
for (size_t i = 0; i < InstMeta.size(); ++i) {
BI->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))
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);
}
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