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4f77caaa3d
multiple type names for the same structural type. Make DTE eliminate all but one of the type names git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11879 91177308-0d34-0410-b5e6-96231b3b80d8
99 lines
3.3 KiB
C++
99 lines
3.3 KiB
C++
//===- DeadTypeElimination.cpp - Eliminate unused types for symbol table --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass is used to cleanup the output of GCC. It eliminate names for types
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// that are unused in the entire translation unit, using the FindUsedTypes pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Analysis/FindUsedTypes.h"
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#include "llvm/Module.h"
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#include "llvm/SymbolTable.h"
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#include "llvm/DerivedTypes.h"
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#include "Support/Statistic.h"
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using namespace llvm;
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namespace {
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struct DTE : public Pass {
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// doPassInitialization - For this pass, it removes global symbol table
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// entries for primitive types. These are never used for linking in GCC and
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// they make the output uglier to look at, so we nuke them.
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//
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// Also, initialize instance variables.
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//
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bool run(Module &M);
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// getAnalysisUsage - This function needs FindUsedTypes to do its job...
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//
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<FindUsedTypes>();
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}
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};
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RegisterOpt<DTE> X("deadtypeelim", "Dead Type Elimination");
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Statistic<>
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NumKilled("deadtypeelim", "Number of unused typenames removed from symtab");
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}
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Pass *llvm::createDeadTypeEliminationPass() {
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return new DTE();
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}
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// ShouldNukeSymtabEntry - Return true if this module level symbol table entry
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// should be eliminated.
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//
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static inline bool ShouldNukeSymtabEntry(const Type *Ty){
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// Nuke all names for primitive types!
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if (Ty->isPrimitiveType()) return true;
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// Nuke all pointers to primitive types as well...
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if (const PointerType *PT = dyn_cast<PointerType>(Ty))
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if (PT->getElementType()->isPrimitiveType()) return true;
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return false;
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}
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// run - For this pass, it removes global symbol table entries for primitive
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// types. These are never used for linking in GCC and they make the output
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// uglier to look at, so we nuke them. Also eliminate types that are never used
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// in the entire program as indicated by FindUsedTypes.
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//
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bool DTE::run(Module &M) {
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bool Changed = false;
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SymbolTable &ST = M.getSymbolTable();
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std::set<const Type *> UsedTypes = getAnalysis<FindUsedTypes>().getTypes();
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// Check the symbol table for superfluous type entries...
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//
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// Grab the 'type' plane of the module symbol...
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SymbolTable::iterator STI = ST.find(Type::TypeTy);
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if (STI != ST.end()) {
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// Loop over all entries in the type plane...
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SymbolTable::VarMap &Plane = STI->second;
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for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();) {
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// If this entry should be unconditionally removed, or if we detect that
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// the type is not used, remove it.
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const Type *RHS = cast<Type>(PI->second);
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if (ShouldNukeSymtabEntry(RHS) || !UsedTypes.count(RHS)) {
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Plane.erase(PI++);
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++NumKilled;
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Changed = true;
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} else {
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++PI;
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// We only need to leave one name for each type.
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UsedTypes.erase(RHS);
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}
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}
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}
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return Changed;
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}
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