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https://github.com/c64scene-ar/llvm-6502.git
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e4d5c441e0
using Function::arg_{iterator|begin|end}. Likewise Module::g* -> Module::global_*.
This patch is contributed by Gabor Greif, thanks!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20597 91177308-0d34-0410-b5e6-96231b3b80d8
395 lines
16 KiB
C++
395 lines
16 KiB
C++
//===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===//
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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 simple pass provides alias and mod/ref information for global values
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// that do not have their address taken, and keeps track of whether functions
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// read or write memory (are "pure"). For this simple (but very common) case,
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// we can provide pretty accurate and useful information.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Instructions.h"
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#include "llvm/Constants.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/SCCIterator.h"
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#include <set>
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using namespace llvm;
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namespace {
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Statistic<>
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NumNonAddrTakenGlobalVars("globalsmodref-aa",
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"Number of global vars without address taken");
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Statistic<>
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NumNonAddrTakenFunctions("globalsmodref-aa",
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"Number of functions without address taken");
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Statistic<>
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NumNoMemFunctions("globalsmodref-aa",
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"Number of functions that do not access memory");
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Statistic<>
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NumReadMemFunctions("globalsmodref-aa",
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"Number of functions that only read memory");
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/// FunctionRecord - One instance of this structure is stored for every
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/// function in the program. Later, the entries for these functions are
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/// removed if the function is found to call an external function (in which
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/// case we know nothing about it.
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struct FunctionRecord {
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/// GlobalInfo - Maintain mod/ref info for all of the globals without
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/// addresses taken that are read or written (transitively) by this
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/// function.
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std::map<GlobalValue*, unsigned> GlobalInfo;
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unsigned getInfoForGlobal(GlobalValue *GV) const {
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std::map<GlobalValue*, unsigned>::const_iterator I = GlobalInfo.find(GV);
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if (I != GlobalInfo.end())
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return I->second;
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return 0;
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}
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/// FunctionEffect - Capture whether or not this function reads or writes to
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/// ANY memory. If not, we can do a lot of aggressive analysis on it.
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unsigned FunctionEffect;
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FunctionRecord() : FunctionEffect(0) {}
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};
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/// GlobalsModRef - The actual analysis pass.
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class GlobalsModRef : public ModulePass, public AliasAnalysis {
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/// NonAddressTakenGlobals - The globals that do not have their addresses
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/// taken.
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std::set<GlobalValue*> NonAddressTakenGlobals;
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/// FunctionInfo - For each function, keep track of what globals are
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/// modified or read.
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std::map<Function*, FunctionRecord> FunctionInfo;
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public:
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bool runOnModule(Module &M) {
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InitializeAliasAnalysis(this); // set up super class
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AnalyzeGlobals(M); // find non-addr taken globals
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AnalyzeCallGraph(getAnalysis<CallGraph>(), M); // Propagate on CG
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return false;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AliasAnalysis::getAnalysisUsage(AU);
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AU.addRequired<CallGraph>();
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AU.setPreservesAll(); // Does not transform code
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}
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//------------------------------------------------
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// Implement the AliasAnalysis API
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//
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AliasResult alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size);
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ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
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ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
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return AliasAnalysis::getModRefInfo(CS1,CS2);
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}
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bool hasNoModRefInfoForCalls() const { return false; }
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/// getModRefBehavior - Return the behavior of the specified function if
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/// called from the specified call site. The call site may be null in which
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/// case the most generic behavior of this function should be returned.
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virtual ModRefBehavior getModRefBehavior(Function *F, CallSite CS,
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std::vector<PointerAccessInfo> *Info) {
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if (FunctionRecord *FR = getFunctionInfo(F))
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if (FR->FunctionEffect == 0)
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return DoesNotAccessMemory;
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else if ((FR->FunctionEffect & Mod) == 0)
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return OnlyReadsMemory;
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return AliasAnalysis::getModRefBehavior(F, CS);
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}
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virtual void deleteValue(Value *V);
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virtual void copyValue(Value *From, Value *To);
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private:
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/// getFunctionInfo - Return the function info for the function, or null if
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/// the function calls an external function (in which case we don't have
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/// anything useful to say about it).
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FunctionRecord *getFunctionInfo(Function *F) {
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std::map<Function*, FunctionRecord>::iterator I = FunctionInfo.find(F);
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if (I != FunctionInfo.end())
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return &I->second;
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return 0;
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}
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void AnalyzeGlobals(Module &M);
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void AnalyzeCallGraph(CallGraph &CG, Module &M);
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void AnalyzeSCC(std::vector<CallGraphNode *> &SCC);
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bool AnalyzeUsesOfGlobal(Value *V, std::vector<Function*> &Readers,
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std::vector<Function*> &Writers);
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};
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RegisterOpt<GlobalsModRef> X("globalsmodref-aa",
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"Simple mod/ref analysis for globals");
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RegisterAnalysisGroup<AliasAnalysis, GlobalsModRef> Y;
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}
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Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); }
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/// AnalyzeGlobalUses - Scan through the users of all of the internal
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/// GlobalValue's in the program. If none of them have their "Address taken"
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/// (really, their address passed to something nontrivial), record this fact,
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/// and record the functions that they are used directly in.
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void GlobalsModRef::AnalyzeGlobals(Module &M) {
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std::vector<Function*> Readers, Writers;
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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if (I->hasInternalLinkage()) {
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if (!AnalyzeUsesOfGlobal(I, Readers, Writers)) {
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// Remember that we are tracking this global.
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NonAddressTakenGlobals.insert(I);
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++NumNonAddrTakenFunctions;
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}
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Readers.clear(); Writers.clear();
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}
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for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
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if (I->hasInternalLinkage()) {
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if (!AnalyzeUsesOfGlobal(I, Readers, Writers)) {
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// Remember that we are tracking this global, and the mod/ref fns
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NonAddressTakenGlobals.insert(I);
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for (unsigned i = 0, e = Readers.size(); i != e; ++i)
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FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref;
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if (!I->isConstant()) // No need to keep track of writers to constants
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for (unsigned i = 0, e = Writers.size(); i != e; ++i)
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FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod;
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++NumNonAddrTakenGlobalVars;
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}
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Readers.clear(); Writers.clear();
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}
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}
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/// AnalyzeUsesOfGlobal - Look at all of the users of the specified global value
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/// derived pointer. If this is used by anything complex (i.e., the address
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/// escapes), return true. Also, while we are at it, keep track of those
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/// functions that read and write to the value.
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bool GlobalsModRef::AnalyzeUsesOfGlobal(Value *V,
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std::vector<Function*> &Readers,
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std::vector<Function*> &Writers) {
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if (!isa<PointerType>(V->getType())) return true;
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
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if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
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Readers.push_back(LI->getParent()->getParent());
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} else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
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if (V == SI->getOperand(0)) return true; // Storing the pointer
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Writers.push_back(SI->getParent()->getParent());
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
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if (AnalyzeUsesOfGlobal(GEP, Readers, Writers)) return true;
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} else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
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// Make sure that this is just the function being called, not that it is
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// passing into the function.
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for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
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if (CI->getOperand(i) == V) return true;
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} else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
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// Make sure that this is just the function being called, not that it is
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// passing into the function.
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for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
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if (CI->getOperand(i) == V) return true;
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} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
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// Make sure that this is just the function being called, not that it is
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// passing into the function.
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for (unsigned i = 3, e = II->getNumOperands(); i != e; ++i)
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if (II->getOperand(i) == V) return true;
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} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
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if (CE->getOpcode() == Instruction::GetElementPtr ||
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CE->getOpcode() == Instruction::Cast) {
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if (AnalyzeUsesOfGlobal(CE, Readers, Writers))
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return true;
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} else {
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return true;
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}
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} else if (GlobalValue *GV = dyn_cast<GlobalValue>(*UI)) {
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if (AnalyzeUsesOfGlobal(GV, Readers, Writers)) return true;
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} else {
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return true;
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}
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return false;
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}
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/// AnalyzeCallGraph - At this point, we know the functions where globals are
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/// immediately stored to and read from. Propagate this information up the call
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/// graph to all callers and compute the mod/ref info for all memory for each
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/// function.
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void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
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// We do a bottom-up SCC traversal of the call graph. In other words, we
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// visit all callees before callers (leaf-first).
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for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I!=E; ++I)
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if ((*I).size() != 1) {
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AnalyzeSCC(*I);
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} else if (Function *F = (*I)[0]->getFunction()) {
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if (!F->isExternal()) {
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// Nonexternal function.
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AnalyzeSCC(*I);
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} else {
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// Otherwise external function. Handle intrinsics and other special
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// cases here.
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if (getAnalysis<AliasAnalysis>().doesNotAccessMemory(F))
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// If it does not access memory, process the function, causing us to
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// realize it doesn't do anything (the body is empty).
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AnalyzeSCC(*I);
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else {
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// Otherwise, don't process it. This will cause us to conservatively
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// assume the worst.
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}
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}
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} else {
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// Do not process the external node, assume the worst.
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}
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}
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void GlobalsModRef::AnalyzeSCC(std::vector<CallGraphNode *> &SCC) {
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assert(!SCC.empty() && "SCC with no functions?");
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FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
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bool CallsExternal = false;
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unsigned FunctionEffect = 0;
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// Collect the mod/ref properties due to called functions. We only compute
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// one mod-ref set
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for (unsigned i = 0, e = SCC.size(); i != e && !CallsExternal; ++i)
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for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
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CI != E; ++CI)
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if (Function *Callee = (*CI)->getFunction()) {
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if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) {
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// Propagate function effect up.
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FunctionEffect |= CalleeFR->FunctionEffect;
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// Incorporate callee's effects on globals into our info.
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for (std::map<GlobalValue*, unsigned>::iterator GI =
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CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end();
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GI != E; ++GI)
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FR.GlobalInfo[GI->first] |= GI->second;
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} else {
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CallsExternal = true;
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break;
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}
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} else {
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CallsExternal = true;
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break;
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}
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// If this SCC calls an external function, we can't say anything about it, so
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// remove all SCC functions from the FunctionInfo map.
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if (CallsExternal) {
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for (unsigned i = 0, e = SCC.size(); i != e; ++i)
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FunctionInfo.erase(SCC[i]->getFunction());
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return;
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}
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// Otherwise, unless we already know that this function mod/refs memory, scan
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// the function bodies to see if there are any explicit loads or stores.
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if (FunctionEffect != ModRef) {
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for (unsigned i = 0, e = SCC.size(); i != e && FunctionEffect != ModRef;++i)
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for (inst_iterator II = inst_begin(SCC[i]->getFunction()),
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E = inst_end(SCC[i]->getFunction());
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II != E && FunctionEffect != ModRef; ++II)
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if (isa<LoadInst>(*II))
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FunctionEffect |= Ref;
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else if (isa<StoreInst>(*II))
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FunctionEffect |= Mod;
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}
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if ((FunctionEffect & Mod) == 0)
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++NumReadMemFunctions;
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if (FunctionEffect == 0)
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++NumNoMemFunctions;
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FR.FunctionEffect = FunctionEffect;
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// Finally, now that we know the full effect on this SCC, clone the
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// information to each function in the SCC.
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for (unsigned i = 1, e = SCC.size(); i != e; ++i)
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FunctionInfo[SCC[i]->getFunction()] = FR;
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}
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/// getUnderlyingObject - This traverses the use chain to figure out what object
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/// the specified value points to. If the value points to, or is derived from,
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/// a global object, return it.
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static const GlobalValue *getUnderlyingObject(const Value *V) {
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if (!isa<PointerType>(V->getType())) return 0;
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// If we are at some type of object... return it.
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if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) return GV;
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// Traverse through different addressing mechanisms...
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if (const Instruction *I = dyn_cast<Instruction>(V)) {
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if (isa<CastInst>(I) || isa<GetElementPtrInst>(I))
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return getUnderlyingObject(I->getOperand(0));
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} else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
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if (CE->getOpcode() == Instruction::Cast ||
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CE->getOpcode() == Instruction::GetElementPtr)
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return getUnderlyingObject(CE->getOperand(0));
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}
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return 0;
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}
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/// alias - If one of the pointers is to a global that we are tracking, and the
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/// other is some random pointer, we know there cannot be an alias, because the
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/// address of the global isn't taken.
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AliasAnalysis::AliasResult
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GlobalsModRef::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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GlobalValue *GV1 = const_cast<GlobalValue*>(getUnderlyingObject(V1));
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GlobalValue *GV2 = const_cast<GlobalValue*>(getUnderlyingObject(V2));
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// If the global's address is taken, pretend we don't know it's a pointer to
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// the global.
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if (GV1 && !NonAddressTakenGlobals.count(GV1)) GV1 = 0;
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if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0;
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if ((GV1 || GV2) && GV1 != GV2)
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return NoAlias;
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return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
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}
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AliasAnalysis::ModRefResult
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GlobalsModRef::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
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unsigned Known = ModRef;
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// If we are asking for mod/ref info of a direct call with a pointer to a
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// global we are tracking, return information if we have it.
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if (GlobalValue *GV = const_cast<GlobalValue*>(getUnderlyingObject(P)))
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if (GV->hasInternalLinkage())
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if (Function *F = CS.getCalledFunction())
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if (NonAddressTakenGlobals.count(GV))
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if (FunctionRecord *FR = getFunctionInfo(F))
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Known = FR->getInfoForGlobal(GV);
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if (Known == NoModRef)
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return NoModRef; // No need to query other mod/ref analyses
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return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, P, Size));
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}
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//===----------------------------------------------------------------------===//
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// Methods to update the analysis as a result of the client transformation.
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//
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void GlobalsModRef::deleteValue(Value *V) {
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if (GlobalValue *GV = dyn_cast<GlobalValue>(V))
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NonAddressTakenGlobals.erase(GV);
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}
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void GlobalsModRef::copyValue(Value *From, Value *To) {
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}
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