1 //===- DeadTypeElimination.cpp - Eliminate unused types for symbol table --===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass is used to cleanup the output of GCC. It eliminate names for types
11 // that are unused in the entire translation unit, using the FindUsedTypes pass.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "deadtypeelim"
16 #include "llvm/Transforms/IPO.h"
17 #include "llvm/Analysis/FindUsedTypes.h"
18 #include "llvm/Module.h"
19 #include "llvm/TypeSymbolTable.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/ADT/Statistic.h"
24 STATISTIC(NumKilled, "Number of unused typenames removed from symtab");
27 struct DTE : public ModulePass {
28 // doPassInitialization - For this pass, it removes global symbol table
29 // entries for primitive types. These are never used for linking in GCC and
30 // they make the output uglier to look at, so we nuke them.
32 // Also, initialize instance variables.
34 bool runOnModule(Module &M);
36 // getAnalysisUsage - This function needs FindUsedTypes to do its job...
38 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
39 AU.addRequired<FindUsedTypes>();
42 RegisterPass<DTE> X("deadtypeelim", "Dead Type Elimination");
45 ModulePass *llvm::createDeadTypeEliminationPass() {
50 // ShouldNukeSymtabEntry - Return true if this module level symbol table entry
51 // should be eliminated.
53 static inline bool ShouldNukeSymtabEntry(const Type *Ty){
54 // Nuke all names for primitive types!
55 if (Ty->isPrimitiveType() || Ty->isInteger())
58 // Nuke all pointers to primitive types as well...
59 if (const PointerType *PT = dyn_cast<PointerType>(Ty))
60 if (PT->getElementType()->isPrimitiveType() ||
61 PT->getElementType()->isInteger())
67 // run - For this pass, it removes global symbol table entries for primitive
68 // types. These are never used for linking in GCC and they make the output
69 // uglier to look at, so we nuke them. Also eliminate types that are never used
70 // in the entire program as indicated by FindUsedTypes.
72 bool DTE::runOnModule(Module &M) {
75 TypeSymbolTable &ST = M.getTypeSymbolTable();
76 std::set<const Type *> UsedTypes = getAnalysis<FindUsedTypes>().getTypes();
78 // Check the symbol table for superfluous type entries...
80 // Grab the 'type' plane of the module symbol...
81 TypeSymbolTable::iterator TI = ST.begin();
82 TypeSymbolTable::iterator TE = ST.end();
84 // If this entry should be unconditionally removed, or if we detect that
85 // the type is not used, remove it.
86 const Type *RHS = TI->second;
87 if (ShouldNukeSymtabEntry(RHS) || !UsedTypes.count(RHS)) {
93 // We only need to leave one name for each type.