mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-20 11:29:24 +00:00
from ModulePass. Instead of implementing Pass::run, then should implement ModulePass::runOnModule. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16436 91177308-0d34-0410-b5e6-96231b3b80d8
505 lines
20 KiB
C++
505 lines
20 KiB
C++
//===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass promotes "by reference" arguments to be "by value" arguments. In
|
|
// practice, this means looking for internal functions that have pointer
|
|
// arguments. If we can prove, through the use of alias analysis, that an
|
|
// argument is *only* loaded, then we can pass the value into the function
|
|
// instead of the address of the value. This can cause recursive simplification
|
|
// of code and lead to the elimination of allocas (especially in C++ template
|
|
// code like the STL).
|
|
//
|
|
// This pass also handles aggregate arguments that are passed into a function,
|
|
// scalarizing them if the elements of the aggregate are only loaded. Note that
|
|
// we refuse to scalarize aggregates which would require passing in more than
|
|
// three operands to the function, because we don't want to pass thousands of
|
|
// operands for a large array or structure!
|
|
//
|
|
// Note that this transformation could also be done for arguments that are only
|
|
// stored to (returning the value instead), but we do not currently handle that
|
|
// case. This case would be best handled when and if we start supporting
|
|
// multiple return values from functions.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "argpromotion"
|
|
#include "llvm/Transforms/IPO.h"
|
|
#include "llvm/Constants.h"
|
|
#include "llvm/DerivedTypes.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/CallGraphSCCPass.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Analysis/CallGraph.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/Support/CallSite.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/ADT/DepthFirstIterator.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/ADT/StringExtras.h"
|
|
#include <set>
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
Statistic<> NumArgumentsPromoted("argpromotion",
|
|
"Number of pointer arguments promoted");
|
|
Statistic<> NumAggregatesPromoted("argpromotion",
|
|
"Number of aggregate arguments promoted");
|
|
Statistic<> NumArgumentsDead("argpromotion",
|
|
"Number of dead pointer args eliminated");
|
|
|
|
/// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
|
|
///
|
|
struct ArgPromotion : public CallGraphSCCPass {
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.addRequired<AliasAnalysis>();
|
|
AU.addRequired<TargetData>();
|
|
CallGraphSCCPass::getAnalysisUsage(AU);
|
|
}
|
|
|
|
virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
|
|
private:
|
|
bool PromoteArguments(CallGraphNode *CGN);
|
|
bool isSafeToPromoteArgument(Argument *Arg) const;
|
|
Function *DoPromotion(Function *F, std::vector<Argument*> &ArgsToPromote);
|
|
};
|
|
|
|
RegisterOpt<ArgPromotion> X("argpromotion",
|
|
"Promote 'by reference' arguments to scalars");
|
|
}
|
|
|
|
ModulePass *llvm::createArgumentPromotionPass() {
|
|
return new ArgPromotion();
|
|
}
|
|
|
|
bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
|
|
bool Changed = false, LocalChange;
|
|
|
|
do { // Iterate until we stop promoting from this SCC.
|
|
LocalChange = false;
|
|
// Attempt to promote arguments from all functions in this SCC.
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i)
|
|
LocalChange |= PromoteArguments(SCC[i]);
|
|
Changed |= LocalChange; // Remember that we changed something.
|
|
} while (LocalChange);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// PromoteArguments - This method checks the specified function to see if there
|
|
/// are any promotable arguments and if it is safe to promote the function (for
|
|
/// example, all callers are direct). If safe to promote some arguments, it
|
|
/// calls the DoPromotion method.
|
|
///
|
|
bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
|
|
Function *F = CGN->getFunction();
|
|
|
|
// Make sure that it is local to this module.
|
|
if (!F || !F->hasInternalLinkage()) return false;
|
|
|
|
// First check: see if there are any pointer arguments! If not, quick exit.
|
|
std::vector<Argument*> PointerArgs;
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
|
|
if (isa<PointerType>(I->getType()))
|
|
PointerArgs.push_back(I);
|
|
if (PointerArgs.empty()) return false;
|
|
|
|
// Second check: make sure that all callers are direct callers. We can't
|
|
// transform functions that have indirect callers.
|
|
for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
|
|
UI != E; ++UI) {
|
|
CallSite CS = CallSite::get(*UI);
|
|
if (!CS.getInstruction()) // "Taking the address" of the function
|
|
return false;
|
|
|
|
// Ensure that this call site is CALLING the function, not passing it as
|
|
// an argument.
|
|
for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
|
|
AI != E; ++AI)
|
|
if (*AI == F) return false; // Passing the function address in!
|
|
}
|
|
|
|
// Check to see which arguments are promotable. If an argument is not
|
|
// promotable, remove it from the PointerArgs vector.
|
|
for (unsigned i = 0; i != PointerArgs.size(); ++i)
|
|
if (!isSafeToPromoteArgument(PointerArgs[i])) {
|
|
std::swap(PointerArgs[i--], PointerArgs.back());
|
|
PointerArgs.pop_back();
|
|
}
|
|
|
|
// No promotable pointer arguments.
|
|
if (PointerArgs.empty()) return false;
|
|
|
|
// Okay, promote all of the arguments are rewrite the callees!
|
|
Function *NewF = DoPromotion(F, PointerArgs);
|
|
|
|
// Update the call graph to know that the old function is gone.
|
|
getAnalysis<CallGraph>().changeFunction(F, NewF);
|
|
return true;
|
|
}
|
|
|
|
|
|
/// isSafeToPromoteArgument - As you might guess from the name of this method,
|
|
/// it checks to see if it is both safe and useful to promote the argument.
|
|
/// This method limits promotion of aggregates to only promote up to three
|
|
/// elements of the aggregate in order to avoid exploding the number of
|
|
/// arguments passed in.
|
|
bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg) const {
|
|
// We can only promote this argument if all of the uses are loads, or are GEP
|
|
// instructions (with constant indices) that are subsequently loaded.
|
|
std::vector<LoadInst*> Loads;
|
|
std::vector<std::vector<ConstantInt*> > GEPIndices;
|
|
for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
|
|
UI != E; ++UI)
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
|
|
if (LI->isVolatile()) return false; // Don't hack volatile loads
|
|
Loads.push_back(LI);
|
|
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
|
|
if (GEP->use_empty()) {
|
|
// Dead GEP's cause trouble later. Just remove them if we run into
|
|
// them.
|
|
getAnalysis<AliasAnalysis>().deleteValue(GEP);
|
|
GEP->getParent()->getInstList().erase(GEP);
|
|
return isSafeToPromoteArgument(Arg);
|
|
}
|
|
// Ensure that all of the indices are constants.
|
|
std::vector<ConstantInt*> Operands;
|
|
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i)))
|
|
Operands.push_back(C);
|
|
else
|
|
return false; // Not a constant operand GEP!
|
|
|
|
// Ensure that the only users of the GEP are load instructions.
|
|
for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
|
|
UI != E; ++UI)
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
|
|
if (LI->isVolatile()) return false; // Don't hack volatile loads
|
|
Loads.push_back(LI);
|
|
} else {
|
|
return false;
|
|
}
|
|
|
|
// See if there is already a GEP with these indices. If not, check to
|
|
// make sure that we aren't promoting too many elements. If so, nothing
|
|
// to do.
|
|
if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) ==
|
|
GEPIndices.end()) {
|
|
if (GEPIndices.size() == 3) {
|
|
DEBUG(std::cerr << "argpromotion disable promoting argument '"
|
|
<< Arg->getName() << "' because it would require adding more "
|
|
<< "than 3 arguments to the function.\n");
|
|
// We limit aggregate promotion to only promoting up to three elements
|
|
// of the aggregate.
|
|
return false;
|
|
}
|
|
GEPIndices.push_back(Operands);
|
|
}
|
|
} else {
|
|
return false; // Not a load or a GEP.
|
|
}
|
|
|
|
if (Loads.empty()) return true; // No users, this is a dead argument.
|
|
|
|
// Okay, now we know that the argument is only used by load instructions. Use
|
|
// alias analysis to check to see if the pointer is guaranteed to not be
|
|
// modified from entry of the function to each of the load instructions.
|
|
Function &F = *Arg->getParent();
|
|
|
|
// Because there could be several/many load instructions, remember which
|
|
// blocks we know to be transparent to the load.
|
|
std::set<BasicBlock*> TranspBlocks;
|
|
|
|
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
|
|
TargetData &TD = getAnalysis<TargetData>();
|
|
|
|
for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
|
|
// Check to see if the load is invalidated from the start of the block to
|
|
// the load itself.
|
|
LoadInst *Load = Loads[i];
|
|
BasicBlock *BB = Load->getParent();
|
|
|
|
const PointerType *LoadTy =
|
|
cast<PointerType>(Load->getOperand(0)->getType());
|
|
unsigned LoadSize = TD.getTypeSize(LoadTy->getElementType());
|
|
|
|
if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
|
|
return false; // Pointer is invalidated!
|
|
|
|
// Now check every path from the entry block to the load for transparency.
|
|
// To do this, we perform a depth first search on the inverse CFG from the
|
|
// loading block.
|
|
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
|
|
for (idf_ext_iterator<BasicBlock*> I = idf_ext_begin(*PI, TranspBlocks),
|
|
E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
|
|
if (AA.canBasicBlockModify(**I, Arg, LoadSize))
|
|
return false;
|
|
}
|
|
|
|
// If the path from the entry of the function to each load is free of
|
|
// instructions that potentially invalidate the load, we can make the
|
|
// transformation!
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
/// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value*
|
|
/// elements are instances of ConstantInt.
|
|
///
|
|
struct GEPIdxComparator {
|
|
bool operator()(const std::vector<Value*> &LHS,
|
|
const std::vector<Value*> &RHS) const {
|
|
unsigned idx = 0;
|
|
for (; idx < LHS.size() && idx < RHS.size(); ++idx) {
|
|
if (LHS[idx] != RHS[idx]) {
|
|
return cast<ConstantInt>(LHS[idx])->getRawValue() <
|
|
cast<ConstantInt>(RHS[idx])->getRawValue();
|
|
}
|
|
}
|
|
|
|
// Return less than if we ran out of stuff in LHS and we didn't run out of
|
|
// stuff in RHS.
|
|
return idx == LHS.size() && idx != RHS.size();
|
|
}
|
|
};
|
|
}
|
|
|
|
|
|
/// DoPromotion - This method actually performs the promotion of the specified
|
|
/// arguments, and returns the new function. At this point, we know that it's
|
|
/// safe to do so.
|
|
Function *ArgPromotion::DoPromotion(Function *F,
|
|
std::vector<Argument*> &Args2Prom) {
|
|
std::set<Argument*> ArgsToPromote(Args2Prom.begin(), Args2Prom.end());
|
|
|
|
// Start by computing a new prototype for the function, which is the same as
|
|
// the old function, but has modified arguments.
|
|
const FunctionType *FTy = F->getFunctionType();
|
|
std::vector<const Type*> Params;
|
|
|
|
typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable;
|
|
|
|
// ScalarizedElements - If we are promoting a pointer that has elements
|
|
// accessed out of it, keep track of which elements are accessed so that we
|
|
// can add one argument for each.
|
|
//
|
|
// Arguments that are directly loaded will have a zero element value here, to
|
|
// handle cases where there are both a direct load and GEP accesses.
|
|
//
|
|
std::map<Argument*, ScalarizeTable> ScalarizedElements;
|
|
|
|
// OriginalLoads - Keep track of a representative load instruction from the
|
|
// original function so that we can tell the alias analysis implementation
|
|
// what the new GEP/Load instructions we are inserting look like.
|
|
std::map<std::vector<Value*>, LoadInst*> OriginalLoads;
|
|
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
|
|
if (!ArgsToPromote.count(I)) {
|
|
Params.push_back(I->getType());
|
|
} else if (I->use_empty()) {
|
|
++NumArgumentsDead;
|
|
} else {
|
|
// Okay, this is being promoted. Check to see if there are any GEP uses
|
|
// of the argument.
|
|
ScalarizeTable &ArgIndices = ScalarizedElements[I];
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
|
|
++UI) {
|
|
Instruction *User = cast<Instruction>(*UI);
|
|
assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
|
|
std::vector<Value*> Indices(User->op_begin()+1, User->op_end());
|
|
ArgIndices.insert(Indices);
|
|
LoadInst *OrigLoad;
|
|
if (LoadInst *L = dyn_cast<LoadInst>(User))
|
|
OrigLoad = L;
|
|
else
|
|
OrigLoad = cast<LoadInst>(User->use_back());
|
|
OriginalLoads[Indices] = OrigLoad;
|
|
}
|
|
|
|
// Add a parameter to the function for each element passed in.
|
|
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
|
|
E = ArgIndices.end(); SI != E; ++SI)
|
|
Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), *SI));
|
|
|
|
if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
|
|
++NumArgumentsPromoted;
|
|
else
|
|
++NumAggregatesPromoted;
|
|
}
|
|
|
|
const Type *RetTy = FTy->getReturnType();
|
|
|
|
// 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::IntTy);
|
|
}
|
|
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(), F->getName());
|
|
F->getParent()->getFunctionList().insert(F, NF);
|
|
|
|
// Get the alias analysis information that we need to update to reflect our
|
|
// changes.
|
|
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
|
|
|
|
// Loop over all of the callers of the function, transforming the call sites
|
|
// to pass in the loaded pointers.
|
|
//
|
|
std::vector<Value*> Args;
|
|
while (!F->use_empty()) {
|
|
CallSite CS = CallSite::get(F->use_back());
|
|
Instruction *Call = CS.getInstruction();
|
|
|
|
// Loop over the operands, inserting GEP and loads in the caller as
|
|
// appropriate.
|
|
CallSite::arg_iterator AI = CS.arg_begin();
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I, ++AI)
|
|
if (!ArgsToPromote.count(I))
|
|
Args.push_back(*AI); // Unmodified argument
|
|
else if (!I->use_empty()) {
|
|
// Non-dead argument: insert GEPs and loads as appropriate.
|
|
ScalarizeTable &ArgIndices = ScalarizedElements[I];
|
|
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
|
|
E = ArgIndices.end(); SI != E; ++SI) {
|
|
Value *V = *AI;
|
|
LoadInst *OrigLoad = OriginalLoads[*SI];
|
|
if (!SI->empty()) {
|
|
V = new GetElementPtrInst(V, *SI, V->getName()+".idx", Call);
|
|
AA.copyValue(OrigLoad->getOperand(0), V);
|
|
}
|
|
Args.push_back(new LoadInst(V, V->getName()+".val", Call));
|
|
AA.copyValue(OrigLoad, Args.back());
|
|
}
|
|
}
|
|
|
|
if (ExtraArgHack)
|
|
Args.push_back(Constant::getNullValue(Type::IntTy));
|
|
|
|
// 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, "", Call);
|
|
} else {
|
|
New = new CallInst(NF, Args, "", Call);
|
|
}
|
|
Args.clear();
|
|
|
|
// Update the alias analysis implementation to know that we are replacing
|
|
// the old call with a new one.
|
|
AA.replaceWithNewValue(Call, New);
|
|
|
|
if (!Call->use_empty()) {
|
|
Call->replaceAllUsesWith(New);
|
|
std::string Name = Call->getName();
|
|
Call->setName("");
|
|
New->setName(Name);
|
|
}
|
|
|
|
// 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.
|
|
//
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(), I2 = NF->abegin();
|
|
I != E; ++I)
|
|
if (!ArgsToPromote.count(I)) {
|
|
// If this is an unmodified argument, move the name and users over to the
|
|
// new version.
|
|
I->replaceAllUsesWith(I2);
|
|
I2->setName(I->getName());
|
|
AA.replaceWithNewValue(I, I2);
|
|
++I2;
|
|
} else if (I->use_empty()) {
|
|
AA.deleteValue(I);
|
|
} else {
|
|
// Otherwise, if we promoted this argument, then all users are load
|
|
// instructions, and all loads should be using the new argument that we
|
|
// added.
|
|
ScalarizeTable &ArgIndices = ScalarizedElements[I];
|
|
|
|
while (!I->use_empty()) {
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
|
|
assert(ArgIndices.begin()->empty() &&
|
|
"Load element should sort to front!");
|
|
I2->setName(I->getName()+".val");
|
|
LI->replaceAllUsesWith(I2);
|
|
AA.replaceWithNewValue(LI, I2);
|
|
LI->getParent()->getInstList().erase(LI);
|
|
DEBUG(std::cerr << "*** Promoted load of argument '" << I->getName()
|
|
<< "' in function '" << F->getName() << "'\n");
|
|
} else {
|
|
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
|
|
std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end());
|
|
|
|
unsigned ArgNo = 0;
|
|
Function::aiterator TheArg = I2;
|
|
for (ScalarizeTable::iterator It = ArgIndices.begin();
|
|
*It != Operands; ++It, ++TheArg) {
|
|
assert(It != ArgIndices.end() && "GEP not handled??");
|
|
}
|
|
|
|
std::string NewName = I->getName();
|
|
for (unsigned i = 0, e = Operands.size(); i != e; ++i)
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i]))
|
|
NewName += "."+itostr((int64_t)CI->getRawValue());
|
|
else
|
|
NewName += ".x";
|
|
TheArg->setName(NewName+".val");
|
|
|
|
DEBUG(std::cerr << "*** Promoted agg argument '" << TheArg->getName()
|
|
<< "' of function '" << F->getName() << "'\n");
|
|
|
|
// All of the uses must be load instructions. Replace them all with
|
|
// the argument specified by ArgNo.
|
|
while (!GEP->use_empty()) {
|
|
LoadInst *L = cast<LoadInst>(GEP->use_back());
|
|
L->replaceAllUsesWith(TheArg);
|
|
AA.replaceWithNewValue(L, TheArg);
|
|
L->getParent()->getInstList().erase(L);
|
|
}
|
|
AA.deleteValue(GEP);
|
|
GEP->getParent()->getInstList().erase(GEP);
|
|
}
|
|
}
|
|
|
|
// Increment I2 past all of the arguments added for this promoted pointer.
|
|
for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
|
|
++I2;
|
|
}
|
|
|
|
// Notify the alias analysis implementation that we inserted a new argument.
|
|
if (ExtraArgHack)
|
|
AA.copyValue(Constant::getNullValue(Type::IntTy), NF->abegin());
|
|
|
|
|
|
// Tell the alias analysis that the old function is about to disappear.
|
|
AA.replaceWithNewValue(F, NF);
|
|
|
|
// Now that the old function is dead, delete it.
|
|
F->getParent()->getFunctionList().erase(F);
|
|
return NF;
|
|
}
|