mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36873 91177308-0d34-0410-b5e6-96231b3b80d8
704 lines
27 KiB
C++
704 lines
27 KiB
C++
//===-- DeadArgumentElimination.cpp - Eliminate dead arguments ------------===//
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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 deletes dead arguments from internal functions. Dead argument
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// elimination removes arguments which are directly dead, as well as arguments
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// only passed into function calls as dead arguments of other functions. This
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// pass also deletes dead arguments in a similar way.
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//
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// This pass is often useful as a cleanup pass to run after aggressive
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// interprocedural passes, which add possibly-dead arguments.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "deadargelim"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/CallingConv.h"
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#include "llvm/Constant.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/Compiler.h"
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#include <set>
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using namespace llvm;
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STATISTIC(NumArgumentsEliminated, "Number of unread args removed");
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STATISTIC(NumRetValsEliminated , "Number of unused return values removed");
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namespace {
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/// DAE - The dead argument elimination pass.
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///
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class VISIBILITY_HIDDEN DAE : public ModulePass {
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/// Liveness enum - During our initial pass over the program, we determine
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/// that things are either definately alive, definately dead, or in need of
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/// interprocedural analysis (MaybeLive).
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///
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enum Liveness { Live, MaybeLive, Dead };
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/// LiveArguments, MaybeLiveArguments, DeadArguments - These sets contain
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/// all of the arguments in the program. The Dead set contains arguments
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/// which are completely dead (never used in the function). The MaybeLive
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/// set contains arguments which are only passed into other function calls,
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/// thus may be live and may be dead. The Live set contains arguments which
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/// are known to be alive.
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///
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std::set<Argument*> DeadArguments, MaybeLiveArguments, LiveArguments;
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/// DeadRetVal, MaybeLiveRetVal, LifeRetVal - These sets contain all of the
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/// functions in the program. The Dead set contains functions whose return
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/// value is known to be dead. The MaybeLive set contains functions whose
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/// return values are only used by return instructions, and the Live set
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/// contains functions whose return values are used, functions that are
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/// external, and functions that already return void.
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///
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std::set<Function*> DeadRetVal, MaybeLiveRetVal, LiveRetVal;
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/// InstructionsToInspect - As we mark arguments and return values
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/// MaybeLive, we keep track of which instructions could make the values
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/// live here. Once the entire program has had the return value and
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/// arguments analyzed, this set is scanned to promote the MaybeLive objects
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/// to be Live if they really are used.
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std::vector<Instruction*> InstructionsToInspect;
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/// CallSites - Keep track of the call sites of functions that have
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/// MaybeLive arguments or return values.
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std::multimap<Function*, CallSite> CallSites;
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public:
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static char ID; // Pass identification, replacement for typeid
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DAE() : ModulePass((intptr_t)&ID) {}
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bool runOnModule(Module &M);
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virtual bool ShouldHackArguments() const { return false; }
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private:
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Liveness getArgumentLiveness(const Argument &A);
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bool isMaybeLiveArgumentNowLive(Argument *Arg);
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bool DeleteDeadVarargs(Function &Fn);
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void SurveyFunction(Function &Fn);
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void MarkArgumentLive(Argument *Arg);
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void MarkRetValLive(Function *F);
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void MarkReturnInstArgumentLive(ReturnInst *RI);
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void RemoveDeadArgumentsFromFunction(Function *F);
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};
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char DAE::ID = 0;
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RegisterPass<DAE> X("deadargelim", "Dead Argument Elimination");
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/// DAH - DeadArgumentHacking pass - Same as dead argument elimination, but
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/// deletes arguments to functions which are external. This is only for use
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/// by bugpoint.
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struct DAH : public DAE {
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static char ID;
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virtual bool ShouldHackArguments() const { return true; }
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};
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char DAH::ID = 0;
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RegisterPass<DAH> Y("deadarghaX0r",
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"Dead Argument Hacking (BUGPOINT USE ONLY; DO NOT USE)");
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}
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/// createDeadArgEliminationPass - This pass removes arguments from functions
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/// which are not used by the body of the function.
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///
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ModulePass *llvm::createDeadArgEliminationPass() { return new DAE(); }
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ModulePass *llvm::createDeadArgHackingPass() { return new DAH(); }
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/// DeleteDeadVarargs - If this is an function that takes a ... list, and if
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/// llvm.vastart is never called, the varargs list is dead for the function.
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bool DAE::DeleteDeadVarargs(Function &Fn) {
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assert(Fn.getFunctionType()->isVarArg() && "Function isn't varargs!");
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if (Fn.isDeclaration() || !Fn.hasInternalLinkage()) return false;
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// Ensure that the function is only directly called.
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for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end(); I != E; ++I) {
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// If this use is anything other than a call site, give up.
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CallSite CS = CallSite::get(*I);
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Instruction *TheCall = CS.getInstruction();
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if (!TheCall) return false; // Not a direct call site?
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// The addr of this function is passed to the call.
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if (I.getOperandNo() != 0) return false;
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}
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// Okay, we know we can transform this function if safe. Scan its body
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// looking for calls to llvm.vastart.
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for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
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if (II->getIntrinsicID() == Intrinsic::vastart)
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return false;
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}
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}
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}
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// If we get here, there are no calls to llvm.vastart in the function body,
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// remove the "..." and adjust all the calls.
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// Start by computing a new prototype for the function, which is the same as
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// the old function, but has fewer arguments.
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const FunctionType *FTy = Fn.getFunctionType();
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std::vector<const Type*> Params(FTy->param_begin(), FTy->param_end());
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FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params, false);
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unsigned NumArgs = Params.size();
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// Create the new function body and insert it into the module...
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Function *NF = new Function(NFTy, Fn.getLinkage());
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NF->setCallingConv(Fn.getCallingConv());
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Fn.getParent()->getFunctionList().insert(&Fn, NF);
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NF->takeName(&Fn);
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// Loop over all of the callers of the function, transforming the call sites
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// to pass in a smaller number of arguments into the new function.
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//
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std::vector<Value*> Args;
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while (!Fn.use_empty()) {
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CallSite CS = CallSite::get(Fn.use_back());
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Instruction *Call = CS.getInstruction();
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// Loop over the operands, dropping extraneous ones at the end of the list.
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Args.assign(CS.arg_begin(), CS.arg_begin()+NumArgs);
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Instruction *New;
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if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
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New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
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&Args[0], Args.size(), "", Call);
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cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
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} else {
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New = new CallInst(NF, &Args[0], Args.size(), "", Call);
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cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
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if (cast<CallInst>(Call)->isTailCall())
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cast<CallInst>(New)->setTailCall();
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}
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Args.clear();
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if (!Call->use_empty())
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Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
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New->takeName(Call);
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// Finally, remove the old call from the program, reducing the use-count of
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// F.
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Call->getParent()->getInstList().erase(Call);
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}
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// Since we have now created the new function, splice the body of the old
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// function right into the new function, leaving the old rotting hulk of the
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// function empty.
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NF->getBasicBlockList().splice(NF->begin(), Fn.getBasicBlockList());
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// Loop over the argument list, transfering uses of the old arguments over to
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// the new arguments, also transfering over the names as well. While we're at
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// it, remove the dead arguments from the DeadArguments list.
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//
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for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
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I2 = NF->arg_begin(); I != E; ++I, ++I2) {
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// Move the name and users over to the new version.
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I->replaceAllUsesWith(I2);
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I2->takeName(I);
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}
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// Finally, nuke the old function.
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Fn.eraseFromParent();
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return true;
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}
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static inline bool CallPassesValueThoughVararg(Instruction *Call,
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const Value *Arg) {
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CallSite CS = CallSite::get(Call);
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const Type *CalledValueTy = CS.getCalledValue()->getType();
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const Type *FTy = cast<PointerType>(CalledValueTy)->getElementType();
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unsigned NumFixedArgs = cast<FunctionType>(FTy)->getNumParams();
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for (CallSite::arg_iterator AI = CS.arg_begin()+NumFixedArgs;
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AI != CS.arg_end(); ++AI)
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if (AI->get() == Arg)
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return true;
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return false;
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}
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// getArgumentLiveness - Inspect an argument, determining if is known Live
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// (used in a computation), MaybeLive (only passed as an argument to a call), or
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// Dead (not used).
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DAE::Liveness DAE::getArgumentLiveness(const Argument &A) {
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const FunctionType *FTy = A.getParent()->getFunctionType();
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// If this is the return value of a struct function, it's not really dead.
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if (FTy->isStructReturn() && &*A.getParent()->arg_begin() == &A)
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return Live;
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if (A.use_empty()) // First check, directly dead?
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return Dead;
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// Scan through all of the uses, looking for non-argument passing uses.
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for (Value::use_const_iterator I = A.use_begin(), E = A.use_end(); I!=E;++I) {
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// Return instructions do not immediately effect liveness.
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if (isa<ReturnInst>(*I))
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continue;
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CallSite CS = CallSite::get(const_cast<User*>(*I));
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if (!CS.getInstruction()) {
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// If its used by something that is not a call or invoke, it's alive!
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return Live;
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}
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// If it's an indirect call, mark it alive...
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Function *Callee = CS.getCalledFunction();
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if (!Callee) return Live;
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// Check to see if it's passed through a va_arg area: if so, we cannot
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// remove it.
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if (CallPassesValueThoughVararg(CS.getInstruction(), &A))
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return Live; // If passed through va_arg area, we cannot remove it
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}
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return MaybeLive; // It must be used, but only as argument to a function
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}
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// SurveyFunction - This performs the initial survey of the specified function,
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// checking out whether or not it uses any of its incoming arguments or whether
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// any callers use the return value. This fills in the
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// (Dead|MaybeLive|Live)(Arguments|RetVal) sets.
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//
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// We consider arguments of non-internal functions to be intrinsically alive as
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// well as arguments to functions which have their "address taken".
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//
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void DAE::SurveyFunction(Function &F) {
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bool FunctionIntrinsicallyLive = false;
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Liveness RetValLiveness = F.getReturnType() == Type::VoidTy ? Live : Dead;
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if (!F.hasInternalLinkage() &&
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(!ShouldHackArguments() || F.getIntrinsicID()))
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FunctionIntrinsicallyLive = true;
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else
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for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) {
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// If this use is anything other than a call site, the function is alive.
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CallSite CS = CallSite::get(*I);
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Instruction *TheCall = CS.getInstruction();
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if (!TheCall) { // Not a direct call site?
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FunctionIntrinsicallyLive = true;
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break;
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}
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// Check to see if the return value is used...
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if (RetValLiveness != Live)
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for (Value::use_iterator I = TheCall->use_begin(),
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E = TheCall->use_end(); I != E; ++I)
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if (isa<ReturnInst>(cast<Instruction>(*I))) {
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RetValLiveness = MaybeLive;
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} else if (isa<CallInst>(cast<Instruction>(*I)) ||
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isa<InvokeInst>(cast<Instruction>(*I))) {
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if (CallPassesValueThoughVararg(cast<Instruction>(*I), TheCall) ||
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!CallSite::get(cast<Instruction>(*I)).getCalledFunction()) {
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RetValLiveness = Live;
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break;
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} else {
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RetValLiveness = MaybeLive;
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}
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} else {
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RetValLiveness = Live;
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break;
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}
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// If the function is PASSED IN as an argument, its address has been taken
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for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
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AI != E; ++AI)
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if (AI->get() == &F) {
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FunctionIntrinsicallyLive = true;
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break;
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}
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if (FunctionIntrinsicallyLive) break;
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}
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if (FunctionIntrinsicallyLive) {
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DOUT << " Intrinsically live fn: " << F.getName() << "\n";
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for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
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AI != E; ++AI)
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LiveArguments.insert(AI);
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LiveRetVal.insert(&F);
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return;
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}
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switch (RetValLiveness) {
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case Live: LiveRetVal.insert(&F); break;
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case MaybeLive: MaybeLiveRetVal.insert(&F); break;
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case Dead: DeadRetVal.insert(&F); break;
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}
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DOUT << " Inspecting args for fn: " << F.getName() << "\n";
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// If it is not intrinsically alive, we know that all users of the
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// function are call sites. Mark all of the arguments live which are
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// directly used, and keep track of all of the call sites of this function
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// if there are any arguments we assume that are dead.
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//
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bool AnyMaybeLiveArgs = false;
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for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end();
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AI != E; ++AI)
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switch (getArgumentLiveness(*AI)) {
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case Live:
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DOUT << " Arg live by use: " << AI->getName() << "\n";
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LiveArguments.insert(AI);
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break;
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case Dead:
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DOUT << " Arg definitely dead: " << AI->getName() <<"\n";
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DeadArguments.insert(AI);
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break;
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case MaybeLive:
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DOUT << " Arg only passed to calls: " << AI->getName() << "\n";
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AnyMaybeLiveArgs = true;
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MaybeLiveArguments.insert(AI);
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break;
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}
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// If there are any "MaybeLive" arguments, we need to check callees of
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// this function when/if they become alive. Record which functions are
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// callees...
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if (AnyMaybeLiveArgs || RetValLiveness == MaybeLive)
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for (Value::use_iterator I = F.use_begin(), E = F.use_end();
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I != E; ++I) {
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if (AnyMaybeLiveArgs)
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CallSites.insert(std::make_pair(&F, CallSite::get(*I)));
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if (RetValLiveness == MaybeLive)
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
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UI != E; ++UI)
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InstructionsToInspect.push_back(cast<Instruction>(*UI));
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}
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}
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// isMaybeLiveArgumentNowLive - Check to see if Arg is alive. At this point, we
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// know that the only uses of Arg are to be passed in as an argument to a
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// function call or return. Check to see if the formal argument passed in is in
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// the LiveArguments set. If so, return true.
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//
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bool DAE::isMaybeLiveArgumentNowLive(Argument *Arg) {
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for (Value::use_iterator I = Arg->use_begin(), E = Arg->use_end(); I!=E; ++I){
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if (isa<ReturnInst>(*I)) {
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if (LiveRetVal.count(Arg->getParent())) return true;
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continue;
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}
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CallSite CS = CallSite::get(*I);
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// We know that this can only be used for direct calls...
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Function *Callee = CS.getCalledFunction();
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// Loop over all of the arguments (because Arg may be passed into the call
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// multiple times) and check to see if any are now alive...
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CallSite::arg_iterator CSAI = CS.arg_begin();
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for (Function::arg_iterator AI = Callee->arg_begin(), E = Callee->arg_end();
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AI != E; ++AI, ++CSAI)
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// If this is the argument we are looking for, check to see if it's alive
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if (*CSAI == Arg && LiveArguments.count(AI))
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return true;
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}
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return false;
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}
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/// MarkArgumentLive - The MaybeLive argument 'Arg' is now known to be alive.
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/// Mark it live in the specified sets and recursively mark arguments in callers
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/// live that are needed to pass in a value.
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///
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void DAE::MarkArgumentLive(Argument *Arg) {
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std::set<Argument*>::iterator It = MaybeLiveArguments.lower_bound(Arg);
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if (It == MaybeLiveArguments.end() || *It != Arg) return;
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DOUT << " MaybeLive argument now live: " << Arg->getName() <<"\n";
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MaybeLiveArguments.erase(It);
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LiveArguments.insert(Arg);
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// Loop over all of the call sites of the function, making any arguments
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// passed in to provide a value for this argument live as necessary.
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//
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Function *Fn = Arg->getParent();
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unsigned ArgNo = std::distance(Fn->arg_begin(), Function::arg_iterator(Arg));
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std::multimap<Function*, CallSite>::iterator I = CallSites.lower_bound(Fn);
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for (; I != CallSites.end() && I->first == Fn; ++I) {
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CallSite CS = I->second;
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Value *ArgVal = *(CS.arg_begin()+ArgNo);
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if (Argument *ActualArg = dyn_cast<Argument>(ArgVal)) {
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MarkArgumentLive(ActualArg);
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} else {
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// If the value passed in at this call site is a return value computed by
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// some other call site, make sure to mark the return value at the other
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// call site as being needed.
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CallSite ArgCS = CallSite::get(ArgVal);
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if (ArgCS.getInstruction())
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if (Function *Fn = ArgCS.getCalledFunction())
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MarkRetValLive(Fn);
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}
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}
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}
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/// MarkArgumentLive - The MaybeLive return value for the specified function is
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/// now known to be alive. Propagate this fact to the return instructions which
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/// produce it.
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void DAE::MarkRetValLive(Function *F) {
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assert(F && "Shame shame, we can't have null pointers here!");
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// Check to see if we already knew it was live
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std::set<Function*>::iterator I = MaybeLiveRetVal.lower_bound(F);
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if (I == MaybeLiveRetVal.end() || *I != F) return; // It's already alive!
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DOUT << " MaybeLive retval now live: " << F->getName() << "\n";
|
|
|
|
MaybeLiveRetVal.erase(I);
|
|
LiveRetVal.insert(F); // It is now known to be live!
|
|
|
|
// Loop over all of the functions, noticing that the return value is now live.
|
|
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
|
|
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
|
|
MarkReturnInstArgumentLive(RI);
|
|
}
|
|
|
|
void DAE::MarkReturnInstArgumentLive(ReturnInst *RI) {
|
|
Value *Op = RI->getOperand(0);
|
|
if (Argument *A = dyn_cast<Argument>(Op)) {
|
|
MarkArgumentLive(A);
|
|
} else if (CallInst *CI = dyn_cast<CallInst>(Op)) {
|
|
if (Function *F = CI->getCalledFunction())
|
|
MarkRetValLive(F);
|
|
} else if (InvokeInst *II = dyn_cast<InvokeInst>(Op)) {
|
|
if (Function *F = II->getCalledFunction())
|
|
MarkRetValLive(F);
|
|
}
|
|
}
|
|
|
|
// RemoveDeadArgumentsFromFunction - We know that F has dead arguments, as
|
|
// specified by the DeadArguments list. Transform the function and all of the
|
|
// callees of the function to not have these arguments.
|
|
//
|
|
void DAE::RemoveDeadArgumentsFromFunction(Function *F) {
|
|
// Start by computing a new prototype for the function, which is the same as
|
|
// the old function, but has fewer arguments.
|
|
const FunctionType *FTy = F->getFunctionType();
|
|
std::vector<const Type*> Params;
|
|
|
|
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
|
|
if (!DeadArguments.count(I))
|
|
Params.push_back(I->getType());
|
|
|
|
const Type *RetTy = FTy->getReturnType();
|
|
if (DeadRetVal.count(F)) {
|
|
RetTy = Type::VoidTy;
|
|
DeadRetVal.erase(F);
|
|
}
|
|
|
|
// Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
|
|
// have zero fixed arguments.
|
|
//
|
|
bool ExtraArgHack = false;
|
|
if (Params.empty() && FTy->isVarArg()) {
|
|
ExtraArgHack = true;
|
|
Params.push_back(Type::Int32Ty);
|
|
}
|
|
|
|
FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
|
|
|
|
// Create the new function body and insert it into the module...
|
|
Function *NF = new Function(NFTy, F->getLinkage());
|
|
NF->setCallingConv(F->getCallingConv());
|
|
F->getParent()->getFunctionList().insert(F, NF);
|
|
NF->takeName(F);
|
|
|
|
// Loop over all of the callers of the function, transforming the call sites
|
|
// to pass in a smaller number of arguments into the new function.
|
|
//
|
|
std::vector<Value*> Args;
|
|
while (!F->use_empty()) {
|
|
CallSite CS = CallSite::get(F->use_back());
|
|
Instruction *Call = CS.getInstruction();
|
|
|
|
// Loop over the operands, deleting dead ones...
|
|
CallSite::arg_iterator AI = CS.arg_begin();
|
|
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
|
|
I != E; ++I, ++AI)
|
|
if (!DeadArguments.count(I)) // Remove operands for dead arguments
|
|
Args.push_back(*AI);
|
|
|
|
if (ExtraArgHack)
|
|
Args.push_back(UndefValue::get(Type::Int32Ty));
|
|
|
|
// Push any varargs arguments on the list
|
|
for (; AI != CS.arg_end(); ++AI)
|
|
Args.push_back(*AI);
|
|
|
|
Instruction *New;
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
|
|
New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
|
|
&Args[0], Args.size(), "", Call);
|
|
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
|
|
} else {
|
|
New = new CallInst(NF, &Args[0], Args.size(), "", Call);
|
|
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
|
|
if (cast<CallInst>(Call)->isTailCall())
|
|
cast<CallInst>(New)->setTailCall();
|
|
}
|
|
Args.clear();
|
|
|
|
if (!Call->use_empty()) {
|
|
if (New->getType() == Type::VoidTy)
|
|
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
|
|
else {
|
|
Call->replaceAllUsesWith(New);
|
|
New->takeName(Call);
|
|
}
|
|
}
|
|
|
|
// Finally, remove the old call from the program, reducing the use-count of
|
|
// F.
|
|
Call->getParent()->getInstList().erase(Call);
|
|
}
|
|
|
|
// Since we have now created the new function, splice the body of the old
|
|
// function right into the new function, leaving the old rotting hulk of the
|
|
// function empty.
|
|
NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
|
|
|
|
// Loop over the argument list, transfering uses of the old arguments over to
|
|
// the new arguments, also transfering over the names as well. While we're at
|
|
// it, remove the dead arguments from the DeadArguments list.
|
|
//
|
|
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
|
|
I2 = NF->arg_begin();
|
|
I != E; ++I)
|
|
if (!DeadArguments.count(I)) {
|
|
// If this is a live argument, move the name and users over to the new
|
|
// version.
|
|
I->replaceAllUsesWith(I2);
|
|
I2->takeName(I);
|
|
++I2;
|
|
} else {
|
|
// If this argument is dead, replace any uses of it with null constants
|
|
// (these are guaranteed to only be operands to call instructions which
|
|
// will later be simplified).
|
|
I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
|
|
DeadArguments.erase(I);
|
|
}
|
|
|
|
// If we change the return value of the function we must rewrite any return
|
|
// instructions. Check this now.
|
|
if (F->getReturnType() != NF->getReturnType())
|
|
for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB)
|
|
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
|
|
new ReturnInst(0, RI);
|
|
BB->getInstList().erase(RI);
|
|
}
|
|
|
|
// Now that the old function is dead, delete it.
|
|
F->getParent()->getFunctionList().erase(F);
|
|
}
|
|
|
|
bool DAE::runOnModule(Module &M) {
|
|
// First phase: loop through the module, determining which arguments are live.
|
|
// We assume all arguments are dead unless proven otherwise (allowing us to
|
|
// determine that dead arguments passed into recursive functions are dead).
|
|
//
|
|
DOUT << "DAE - Determining liveness\n";
|
|
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
|
|
Function &F = *I++;
|
|
if (F.getFunctionType()->isVarArg())
|
|
if (DeleteDeadVarargs(F))
|
|
continue;
|
|
|
|
SurveyFunction(F);
|
|
}
|
|
|
|
// Loop over the instructions to inspect, propagating liveness among arguments
|
|
// and return values which are MaybeLive.
|
|
|
|
while (!InstructionsToInspect.empty()) {
|
|
Instruction *I = InstructionsToInspect.back();
|
|
InstructionsToInspect.pop_back();
|
|
|
|
if (ReturnInst *RI = dyn_cast<ReturnInst>(I)) {
|
|
// For return instructions, we just have to check to see if the return
|
|
// value for the current function is known now to be alive. If so, any
|
|
// arguments used by it are now alive, and any call instruction return
|
|
// value is alive as well.
|
|
if (LiveRetVal.count(RI->getParent()->getParent()))
|
|
MarkReturnInstArgumentLive(RI);
|
|
|
|
} else {
|
|
CallSite CS = CallSite::get(I);
|
|
assert(CS.getInstruction() && "Unknown instruction for the I2I list!");
|
|
|
|
Function *Callee = CS.getCalledFunction();
|
|
|
|
// If we found a call or invoke instruction on this list, that means that
|
|
// an argument of the function is a call instruction. If the argument is
|
|
// live, then the return value of the called instruction is now live.
|
|
//
|
|
CallSite::arg_iterator AI = CS.arg_begin(); // ActualIterator
|
|
for (Function::arg_iterator FI = Callee->arg_begin(),
|
|
E = Callee->arg_end(); FI != E; ++AI, ++FI) {
|
|
// If this argument is another call...
|
|
CallSite ArgCS = CallSite::get(*AI);
|
|
if (ArgCS.getInstruction() && LiveArguments.count(FI))
|
|
if (Function *Callee = ArgCS.getCalledFunction())
|
|
MarkRetValLive(Callee);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Now we loop over all of the MaybeLive arguments, promoting them to be live
|
|
// arguments if one of the calls that uses the arguments to the calls they are
|
|
// passed into requires them to be live. Of course this could make other
|
|
// arguments live, so process callers recursively.
|
|
//
|
|
// Because elements can be removed from the MaybeLiveArguments set, copy it to
|
|
// a temporary vector.
|
|
//
|
|
std::vector<Argument*> TmpArgList(MaybeLiveArguments.begin(),
|
|
MaybeLiveArguments.end());
|
|
for (unsigned i = 0, e = TmpArgList.size(); i != e; ++i) {
|
|
Argument *MLA = TmpArgList[i];
|
|
if (MaybeLiveArguments.count(MLA) &&
|
|
isMaybeLiveArgumentNowLive(MLA))
|
|
MarkArgumentLive(MLA);
|
|
}
|
|
|
|
// Recover memory early...
|
|
CallSites.clear();
|
|
|
|
// At this point, we know that all arguments in DeadArguments and
|
|
// MaybeLiveArguments are dead. If the two sets are empty, there is nothing
|
|
// to do.
|
|
if (MaybeLiveArguments.empty() && DeadArguments.empty() &&
|
|
MaybeLiveRetVal.empty() && DeadRetVal.empty())
|
|
return false;
|
|
|
|
// Otherwise, compact into one set, and start eliminating the arguments from
|
|
// the functions.
|
|
DeadArguments.insert(MaybeLiveArguments.begin(), MaybeLiveArguments.end());
|
|
MaybeLiveArguments.clear();
|
|
DeadRetVal.insert(MaybeLiveRetVal.begin(), MaybeLiveRetVal.end());
|
|
MaybeLiveRetVal.clear();
|
|
|
|
LiveArguments.clear();
|
|
LiveRetVal.clear();
|
|
|
|
NumArgumentsEliminated += DeadArguments.size();
|
|
NumRetValsEliminated += DeadRetVal.size();
|
|
while (!DeadArguments.empty())
|
|
RemoveDeadArgumentsFromFunction((*DeadArguments.begin())->getParent());
|
|
|
|
while (!DeadRetVal.empty())
|
|
RemoveDeadArgumentsFromFunction(*DeadRetVal.begin());
|
|
return true;
|
|
}
|