1 //===- DeadTypeElimination.cpp - Eliminate unused types for symbol table --===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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"
22 #include "llvm/Support/Compiler.h"
25 STATISTIC(NumKilled, "Number of unused typenames removed from symtab");
28 struct VISIBILITY_HIDDEN DTE : public ModulePass {
29 static char ID; // Pass identification, replacement for typeid
30 DTE() : ModulePass((intptr_t)&ID) {}
32 // doPassInitialization - For this pass, it removes global symbol table
33 // entries for primitive types. These are never used for linking in GCC and
34 // they make the output uglier to look at, so we nuke them.
36 // Also, initialize instance variables.
38 bool runOnModule(Module &M);
40 // getAnalysisUsage - This function needs FindUsedTypes to do its job...
42 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
43 AU.addRequired<FindUsedTypes>();
49 static RegisterPass<DTE> X("deadtypeelim", "Dead Type Elimination");
51 ModulePass *llvm::createDeadTypeEliminationPass() {
56 // ShouldNukeSymtabEntry - Return true if this module level symbol table entry
57 // should be eliminated.
59 static inline bool ShouldNukeSymtabEntry(const Type *Ty){
60 // Nuke all names for primitive types!
61 if (Ty->isPrimitiveType() || Ty->isInteger())
64 // Nuke all pointers to primitive types as well...
65 if (const PointerType *PT = dyn_cast<PointerType>(Ty))
66 if (PT->getElementType()->isPrimitiveType() ||
67 PT->getElementType()->isInteger())
73 // run - For this pass, it removes global symbol table entries for primitive
74 // types. These are never used for linking in GCC and they make the output
75 // uglier to look at, so we nuke them. Also eliminate types that are never used
76 // in the entire program as indicated by FindUsedTypes.
78 bool DTE::runOnModule(Module &M) {
81 TypeSymbolTable &ST = M.getTypeSymbolTable();
82 std::set<const Type *> UsedTypes = getAnalysis<FindUsedTypes>().getTypes();
84 // Check the symbol table for superfluous type entries...
86 // Grab the 'type' plane of the module symbol...
87 TypeSymbolTable::iterator TI = ST.begin();
88 TypeSymbolTable::iterator TE = ST.end();
90 // If this entry should be unconditionally removed, or if we detect that
91 // the type is not used, remove it.
92 const Type *RHS = TI->second;
93 if (ShouldNukeSymtabEntry(RHS) || !UsedTypes.count(RHS)) {
99 // We only need to leave one name for each type.
100 UsedTypes.erase(RHS);