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//===- DeadTypeElimination.cpp - Eliminate unused types for symbol table --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass is used to cleanup the output of GCC. It eliminate names for types
// that are unused in the entire translation unit, using the FindUsedTypes pass.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "deadtypeelim"
#include "llvm/Transforms/IPO.h"
#include "llvm/Analysis/FindUsedTypes.h"
#include "llvm/Module.h"
#include "llvm/TypeSymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumKilled, "Number of unused typenames removed from symtab");
namespace {
struct DTE : public ModulePass {
static char ID; // Pass identification, replacement for typeid
DTE() : ModulePass(&ID) {}
// doPassInitialization - For this pass, it removes global symbol table
// entries for primitive types. These are never used for linking in GCC and
// they make the output uglier to look at, so we nuke them.
//
// Also, initialize instance variables.
//
bool runOnModule(Module &M);
// getAnalysisUsage - This function needs FindUsedTypes to do its job...
//
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<FindUsedTypes>();
}
};
}
char DTE::ID = 0;
static RegisterPass<DTE> X("deadtypeelim", "Dead Type Elimination");
ModulePass *llvm::createDeadTypeEliminationPass() {
return new DTE();
}
// ShouldNukeSymtabEntry - Return true if this module level symbol table entry
// should be eliminated.
//
static inline bool ShouldNukeSymtabEntry(const Type *Ty){
// Nuke all names for primitive types!
if (Ty->isPrimitiveType() || Ty->isIntegerTy())
return true;
// Nuke all pointers to primitive types as well...
if (const PointerType *PT = dyn_cast<PointerType>(Ty))
if (PT->getElementType()->isPrimitiveType() ||
PT->getElementType()->isIntegerTy())
return true;
return false;
}
// run - For this pass, it removes global symbol table entries for primitive
// types. These are never used for linking in GCC and they make the output
// uglier to look at, so we nuke them. Also eliminate types that are never used
// in the entire program as indicated by FindUsedTypes.
//
bool DTE::runOnModule(Module &M) {
bool Changed = false;
TypeSymbolTable &ST = M.getTypeSymbolTable();
std::set<const Type *> UsedTypes = getAnalysis<FindUsedTypes>().getTypes();
// Check the symbol table for superfluous type entries...
//
// Grab the 'type' plane of the module symbol...
TypeSymbolTable::iterator TI = ST.begin();
TypeSymbolTable::iterator TE = ST.end();
while ( TI != TE ) {
// If this entry should be unconditionally removed, or if we detect that
// the type is not used, remove it.
const Type *RHS = TI->second;
if (ShouldNukeSymtabEntry(RHS) || !UsedTypes.count(RHS)) {
ST.remove(TI++);
++NumKilled;
Changed = true;
} else {
++TI;
// We only need to leave one name for each type.
UsedTypes.erase(RHS);
}
}
return Changed;
}
// vim: sw=2
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