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diff --git a/gnu/llvm/lib/Transforms/IPO/GlobalDCE.cpp b/gnu/llvm/lib/Transforms/IPO/GlobalDCE.cpp
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-//===-- GlobalDCE.cpp - DCE unreachable internal functions ----------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This transform is designed to eliminate unreachable internal globals from the
-// program. It uses an aggressive algorithm, searching out globals that are
-// known to be alive. After it finds all of the globals which are needed, it
-// deletes whatever is left over. This allows it to delete recursive chunks of
-// the program which are unreachable.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/IPO/GlobalDCE.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Transforms/IPO.h"
-#include "llvm/Transforms/Utils/CtorUtils.h"
-#include "llvm/Transforms/Utils/GlobalStatus.h"
-
-using namespace llvm;
-
-#define DEBUG_TYPE "globaldce"
-
-STATISTIC(NumAliases , "Number of global aliases removed");
-STATISTIC(NumFunctions, "Number of functions removed");
-STATISTIC(NumIFuncs, "Number of indirect functions removed");
-STATISTIC(NumVariables, "Number of global variables removed");
-
-namespace {
- class GlobalDCELegacyPass : public ModulePass {
- public:
- static char ID; // Pass identification, replacement for typeid
- GlobalDCELegacyPass() : ModulePass(ID) {
- initializeGlobalDCELegacyPassPass(*PassRegistry::getPassRegistry());
- }
-
- // run - Do the GlobalDCE pass on the specified module, optionally updating
- // the specified callgraph to reflect the changes.
- //
- bool runOnModule(Module &M) override {
- if (skipModule(M))
- return false;
-
- // We need a minimally functional dummy module analysis manager. It needs
- // to at least know about the possibility of proxying a function analysis
- // manager.
- FunctionAnalysisManager DummyFAM;
- ModuleAnalysisManager DummyMAM;
- DummyMAM.registerPass(
- [&] { return FunctionAnalysisManagerModuleProxy(DummyFAM); });
-
- auto PA = Impl.run(M, DummyMAM);
- return !PA.areAllPreserved();
- }
-
- private:
- GlobalDCEPass Impl;
- };
-}
-
-char GlobalDCELegacyPass::ID = 0;
-INITIALIZE_PASS(GlobalDCELegacyPass, "globaldce",
- "Dead Global Elimination", false, false)
-
-// Public interface to the GlobalDCEPass.
-ModulePass *llvm::createGlobalDCEPass() {
- return new GlobalDCELegacyPass();
-}
-
-/// Returns true if F is effectively empty.
-static bool isEmptyFunction(Function *F) {
- BasicBlock &Entry = F->getEntryBlock();
- for (auto &I : Entry) {
- if (isa<DbgInfoIntrinsic>(I))
- continue;
- if (auto *RI = dyn_cast<ReturnInst>(&I))
- return !RI->getReturnValue();
- break;
- }
- return false;
-}
-
-/// Compute the set of GlobalValue that depends from V.
-/// The recursion stops as soon as a GlobalValue is met.
-void GlobalDCEPass::ComputeDependencies(Value *V,
- SmallPtrSetImpl<GlobalValue *> &Deps) {
- if (auto *I = dyn_cast<Instruction>(V)) {
- Function *Parent = I->getParent()->getParent();
- Deps.insert(Parent);
- } else if (auto *GV = dyn_cast<GlobalValue>(V)) {
- Deps.insert(GV);
- } else if (auto *CE = dyn_cast<Constant>(V)) {
- // Avoid walking the whole tree of a big ConstantExprs multiple times.
- auto Where = ConstantDependenciesCache.find(CE);
- if (Where != ConstantDependenciesCache.end()) {
- auto const &K = Where->second;
- Deps.insert(K.begin(), K.end());
- } else {
- SmallPtrSetImpl<GlobalValue *> &LocalDeps = ConstantDependenciesCache[CE];
- for (User *CEUser : CE->users())
- ComputeDependencies(CEUser, LocalDeps);
- Deps.insert(LocalDeps.begin(), LocalDeps.end());
- }
- }
-}
-
-void GlobalDCEPass::UpdateGVDependencies(GlobalValue &GV) {
- SmallPtrSet<GlobalValue *, 8> Deps;
- for (User *User : GV.users())
- ComputeDependencies(User, Deps);
- Deps.erase(&GV); // Remove self-reference.
- for (GlobalValue *GVU : Deps) {
- GVDependencies[GVU].insert(&GV);
- }
-}
-
-/// Mark Global value as Live
-void GlobalDCEPass::MarkLive(GlobalValue &GV,
- SmallVectorImpl<GlobalValue *> *Updates) {
- auto const Ret = AliveGlobals.insert(&GV);
- if (!Ret.second)
- return;
-
- if (Updates)
- Updates->push_back(&GV);
- if (Comdat *C = GV.getComdat()) {
- for (auto &&CM : make_range(ComdatMembers.equal_range(C)))
- MarkLive(*CM.second, Updates); // Recursion depth is only two because only
- // globals in the same comdat are visited.
- }
-}
-
-PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
- bool Changed = false;
-
- // The algorithm first computes the set L of global variables that are
- // trivially live. Then it walks the initialization of these variables to
- // compute the globals used to initialize them, which effectively builds a
- // directed graph where nodes are global variables, and an edge from A to B
- // means B is used to initialize A. Finally, it propagates the liveness
- // information through the graph starting from the nodes in L. Nodes note
- // marked as alive are discarded.
-
- // Remove empty functions from the global ctors list.
- Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
-
- // Collect the set of members for each comdat.
- for (Function &F : M)
- if (Comdat *C = F.getComdat())
- ComdatMembers.insert(std::make_pair(C, &F));
- for (GlobalVariable &GV : M.globals())
- if (Comdat *C = GV.getComdat())
- ComdatMembers.insert(std::make_pair(C, &GV));
- for (GlobalAlias &GA : M.aliases())
- if (Comdat *C = GA.getComdat())
- ComdatMembers.insert(std::make_pair(C, &GA));
-
- // Loop over the module, adding globals which are obviously necessary.
- for (GlobalObject &GO : M.global_objects()) {
- Changed |= RemoveUnusedGlobalValue(GO);
- // Functions with external linkage are needed if they have a body.
- // Externally visible & appending globals are needed, if they have an
- // initializer.
- if (!GO.isDeclaration())
- if (!GO.isDiscardableIfUnused())
- MarkLive(GO);
-
- UpdateGVDependencies(GO);
- }
-
- // Compute direct dependencies of aliases.
- for (GlobalAlias &GA : M.aliases()) {
- Changed |= RemoveUnusedGlobalValue(GA);
- // Externally visible aliases are needed.
- if (!GA.isDiscardableIfUnused())
- MarkLive(GA);
-
- UpdateGVDependencies(GA);
- }
-
- // Compute direct dependencies of ifuncs.
- for (GlobalIFunc &GIF : M.ifuncs()) {
- Changed |= RemoveUnusedGlobalValue(GIF);
- // Externally visible ifuncs are needed.
- if (!GIF.isDiscardableIfUnused())
- MarkLive(GIF);
-
- UpdateGVDependencies(GIF);
- }
-
- // Propagate liveness from collected Global Values through the computed
- // dependencies.
- SmallVector<GlobalValue *, 8> NewLiveGVs{AliveGlobals.begin(),
- AliveGlobals.end()};
- while (!NewLiveGVs.empty()) {
- GlobalValue *LGV = NewLiveGVs.pop_back_val();
- for (auto *GVD : GVDependencies[LGV])
- MarkLive(*GVD, &NewLiveGVs);
- }
-
- // Now that all globals which are needed are in the AliveGlobals set, we loop
- // through the program, deleting those which are not alive.
- //
-
- // The first pass is to drop initializers of global variables which are dead.
- std::vector<GlobalVariable *> DeadGlobalVars; // Keep track of dead globals
- for (GlobalVariable &GV : M.globals())
- if (!AliveGlobals.count(&GV)) {
- DeadGlobalVars.push_back(&GV); // Keep track of dead globals
- if (GV.hasInitializer()) {
- Constant *Init = GV.getInitializer();
- GV.setInitializer(nullptr);
- if (isSafeToDestroyConstant(Init))
- Init->destroyConstant();
- }
- }
-
- // The second pass drops the bodies of functions which are dead...
- std::vector<Function *> DeadFunctions;
- for (Function &F : M)
- if (!AliveGlobals.count(&F)) {
- DeadFunctions.push_back(&F); // Keep track of dead globals
- if (!F.isDeclaration())
- F.deleteBody();
- }
-
- // The third pass drops targets of aliases which are dead...
- std::vector<GlobalAlias*> DeadAliases;
- for (GlobalAlias &GA : M.aliases())
- if (!AliveGlobals.count(&GA)) {
- DeadAliases.push_back(&GA);
- GA.setAliasee(nullptr);
- }
-
- // The fourth pass drops targets of ifuncs which are dead...
- std::vector<GlobalIFunc*> DeadIFuncs;
- for (GlobalIFunc &GIF : M.ifuncs())
- if (!AliveGlobals.count(&GIF)) {
- DeadIFuncs.push_back(&GIF);
- GIF.setResolver(nullptr);
- }
-
- // Now that all interferences have been dropped, delete the actual objects
- // themselves.
- auto EraseUnusedGlobalValue = [&](GlobalValue *GV) {
- RemoveUnusedGlobalValue(*GV);
- GV->eraseFromParent();
- Changed = true;
- };
-
- NumFunctions += DeadFunctions.size();
- for (Function *F : DeadFunctions)
- EraseUnusedGlobalValue(F);
-
- NumVariables += DeadGlobalVars.size();
- for (GlobalVariable *GV : DeadGlobalVars)
- EraseUnusedGlobalValue(GV);
-
- NumAliases += DeadAliases.size();
- for (GlobalAlias *GA : DeadAliases)
- EraseUnusedGlobalValue(GA);
-
- NumIFuncs += DeadIFuncs.size();
- for (GlobalIFunc *GIF : DeadIFuncs)
- EraseUnusedGlobalValue(GIF);
-
- // Make sure that all memory is released
- AliveGlobals.clear();
- ConstantDependenciesCache.clear();
- GVDependencies.clear();
- ComdatMembers.clear();
-
- if (Changed)
- return PreservedAnalyses::none();
- return PreservedAnalyses::all();
-}
-
-// RemoveUnusedGlobalValue - Loop over all of the uses of the specified
-// GlobalValue, looking for the constant pointer ref that may be pointing to it.
-// If found, check to see if the constant pointer ref is safe to destroy, and if
-// so, nuke it. This will reduce the reference count on the global value, which
-// might make it deader.
-//
-bool GlobalDCEPass::RemoveUnusedGlobalValue(GlobalValue &GV) {
- if (GV.use_empty())
- return false;
- GV.removeDeadConstantUsers();
- return GV.use_empty();
-}
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