1 //===- DeadTypeElimination.cpp - Eliminate unused types for symbol table --===//
3 // This pass is used to cleanup the output of GCC. It eliminate names for types
4 // that are unused in the entire translation unit, using the FindUsedTypes pass.
6 //===----------------------------------------------------------------------===//
8 #include "llvm/Transforms/IPO.h"
9 #include "llvm/Analysis/FindUsedTypes.h"
10 #include "llvm/Module.h"
11 #include "llvm/SymbolTable.h"
12 #include "llvm/DerivedTypes.h"
13 #include "Support/Statistic.h"
16 struct DTE : public Pass {
17 // doPassInitialization - For this pass, it removes global symbol table
18 // entries for primitive types. These are never used for linking in GCC and
19 // they make the output uglier to look at, so we nuke them.
21 // Also, initialize instance variables.
25 // getAnalysisUsage - This function needs FindUsedTypes to do its job...
27 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
28 AU.addRequired<FindUsedTypes>();
31 RegisterOpt<DTE> X("deadtypeelim", "Dead Type Elimination");
33 NumKilled("deadtypeelim", "Number of unused typenames removed from symtab");
36 Pass *createDeadTypeEliminationPass() {
42 // ShouldNukSymtabEntry - Return true if this module level symbol table entry
43 // should be eliminated.
45 static inline bool ShouldNukeSymtabEntry(const std::pair<std::string,Value*>&E){
46 // Nuke all names for primitive types!
47 if (cast<Type>(E.second)->isPrimitiveType()) return true;
49 // Nuke all pointers to primitive types as well...
50 if (const PointerType *PT = dyn_cast<PointerType>(E.second))
51 if (PT->getElementType()->isPrimitiveType()) return true;
56 // run - For this pass, it removes global symbol table entries for primitive
57 // types. These are never used for linking in GCC and they make the output
58 // uglier to look at, so we nuke them. Also eliminate types that are never used
59 // in the entire program as indicated by FindUsedTypes.
61 bool DTE::run(Module &M) {
64 SymbolTable &ST = M.getSymbolTable();
65 const std::set<const Type *> &UsedTypes =
66 getAnalysis<FindUsedTypes>().getTypes();
68 // Check the symbol table for superfluous type entries...
70 // Grab the 'type' plane of the module symbol...
71 SymbolTable::iterator STI = ST.find(Type::TypeTy);
72 if (STI != ST.end()) {
73 // Loop over all entries in the type plane...
74 SymbolTable::VarMap &Plane = STI->second;
75 for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
76 // If this entry should be unconditionally removed, or if we detect that
77 // the type is not used, remove it.
78 if (ShouldNukeSymtabEntry(*PI) ||
79 !UsedTypes.count(cast<Type>(PI->second))) {
80 SymbolTable::VarMap::iterator PJ = PI++;