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Add BasicInliner interface.

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This interface allows clients to inline bunch of functions with module
level call graph information.:wq



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40486 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel
2007-07-25 18:00:25 +00:00
parent b4d2cac15b
commit 6899b31422
5 changed files with 553 additions and 246 deletions
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lib/Transforms/IPO/InlineSimple.cpp
+6 -246
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@@ -22,46 +22,22 @@
#include "llvm/Support/Compiler.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/InlinerPass.h"
#include "llvm/Transforms/Utils/InlineCost.h"
#include <set>
using namespace llvm;
namespace {
struct VISIBILITY_HIDDEN ArgInfo {
unsigned ConstantWeight;
unsigned AllocaWeight;
ArgInfo(unsigned CWeight, unsigned AWeight)
: ConstantWeight(CWeight), AllocaWeight(AWeight) {}
};
// FunctionInfo - For each function, calculate the size of it in blocks and
// instructions.
struct VISIBILITY_HIDDEN FunctionInfo {
// NumInsts, NumBlocks - Keep track of how large each function is, which is
// used to estimate the code size cost of inlining it.
unsigned NumInsts, NumBlocks;
// ArgumentWeights - Each formal argument of the function is inspected to
// see if it is used in any contexts where making it a constant or alloca
// would reduce the code size. If so, we add some value to the argument
// entry here.
std::vector<ArgInfo> ArgumentWeights;
FunctionInfo() : NumInsts(0), NumBlocks(0) {}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void analyzeFunction(Function *F);
};
class VISIBILITY_HIDDEN SimpleInliner : public Inliner {
std::map<const Function*, FunctionInfo> CachedFunctionInfo;
std::set<const Function*> NeverInline; // Functions that are never inlined
InlineCostAnalyzer CA;
public:
SimpleInliner() : Inliner(&ID) {}
static char ID; // Pass identification, replacement for typeid
int getInlineCost(CallSite CS);
int getInlineCost(CallSite CS) {
return CA.getInlineCost(CS, NeverInline);
}
virtual bool doInitialization(CallGraph &CG);
};
char SimpleInliner::ID = 0;
@@ -70,223 +46,6 @@ namespace {
Pass *llvm::createFunctionInliningPass() { return new SimpleInliner(); }
// CountCodeReductionForConstant - Figure out an approximation for how many
// instructions will be constant folded if the specified value is constant.
//
static unsigned CountCodeReductionForConstant(Value *V) {
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (isa<BranchInst>(*UI))
Reduction += 40; // Eliminating a conditional branch is a big win
else if (SwitchInst *SI = dyn_cast<SwitchInst>(*UI))
// Eliminating a switch is a big win, proportional to the number of edges
// deleted.
Reduction += (SI->getNumSuccessors()-1) * 40;
else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += CI->getCalledValue() == V ? 500 : 0;
} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += II->getCalledValue() == V ? 500 : 0;
} else {
// Figure out if this instruction will be removed due to simple constant
// propagation.
Instruction &Inst = cast<Instruction>(**UI);
bool AllOperandsConstant = true;
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {
AllOperandsConstant = false;
break;
}
if (AllOperandsConstant) {
// We will get to remove this instruction...
Reduction += 7;
// And any other instructions that use it which become constants
// themselves.
Reduction += CountCodeReductionForConstant(&Inst);
}
}
return Reduction;
}
// CountCodeReductionForAlloca - Figure out an approximation of how much smaller
// the function will be if it is inlined into a context where an argument
// becomes an alloca.
//
static unsigned CountCodeReductionForAlloca(Value *V) {
if (!isa<PointerType>(V->getType())) return 0; // Not a pointer
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
Instruction *I = cast<Instruction>(*UI);
if (isa<LoadInst>(I) || isa<StoreInst>(I))
Reduction += 10;
else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
// If the GEP has variable indices, we won't be able to do much with it.
for (Instruction::op_iterator I = GEP->op_begin()+1, E = GEP->op_end();
I != E; ++I)
if (!isa<Constant>(*I)) return 0;
Reduction += CountCodeReductionForAlloca(GEP)+15;
} else {
// If there is some other strange instruction, we're not going to be able
// to do much if we inline this.
return 0;
}
}
return Reduction;
}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void FunctionInfo::analyzeFunction(Function *F) {
unsigned NumInsts = 0, NumBlocks = 0;
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 10.
for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
II != E; ++II) {
if (isa<DbgInfoIntrinsic>(II)) continue; // Debug intrinsics don't count.
// Noop casts, including ptr <-> int, don't count.
if (const CastInst *CI = dyn_cast<CastInst>(II)) {
if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) ||
isa<PtrToIntInst>(CI))
continue;
} else if (const GetElementPtrInst *GEPI =
dyn_cast<GetElementPtrInst>(II)) {
// If a GEP has all constant indices, it will probably be folded with
// a load/store.
bool AllConstant = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(GEPI->getOperand(i))) {
AllConstant = false;
break;
}
if (AllConstant) continue;
}
++NumInsts;
}
++NumBlocks;
}
this->NumBlocks = NumBlocks;
this->NumInsts = NumInsts;
// Check out all of the arguments to the function, figuring out how much
// code can be eliminated if one of the arguments is a constant.
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
ArgumentWeights.push_back(ArgInfo(CountCodeReductionForConstant(I),
CountCodeReductionForAlloca(I)));
}
// getInlineCost - The heuristic used to determine if we should inline the
// function call or not.
//
int SimpleInliner::getInlineCost(CallSite CS) {
Instruction *TheCall = CS.getInstruction();
Function *Callee = CS.getCalledFunction();
const Function *Caller = TheCall->getParent()->getParent();
// Don't inline a directly recursive call.
if (Caller == Callee ||
// Don't inline functions which can be redefined at link-time to mean
// something else. link-once linkage is ok though.
Callee->hasWeakLinkage() ||
// Don't inline functions marked noinline.
NeverInline.count(Callee))
return 2000000000;
// InlineCost - This value measures how good of an inline candidate this call
// site is to inline. A lower inline cost make is more likely for the call to
// be inlined. This value may go negative.
//
int InlineCost = 0;
// If there is only one call of the function, and it has internal linkage,
// make it almost guaranteed to be inlined.
//
if (Callee->hasInternalLinkage() && Callee->hasOneUse())
InlineCost -= 30000;
// If this function uses the coldcc calling convention, prefer not to inline
// it.
if (Callee->getCallingConv() == CallingConv::Cold)
InlineCost += 2000;
// If the instruction after the call, or if the normal destination of the
// invoke is an unreachable instruction, the function is noreturn. As such,
// there is little point in inlining this.
if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
if (isa<UnreachableInst>(II->getNormalDest()->begin()))
InlineCost += 10000;
} else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall)))
InlineCost += 10000;
// Get information about the callee...
FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
// If we haven't calculated this information yet, do so now.
if (CalleeFI.NumBlocks == 0)
CalleeFI.analyzeFunction(Callee);
// Add to the inline quality for properties that make the call valuable to
// inline. This includes factors that indicate that the result of inlining
// the function will be optimizable. Currently this just looks at arguments
// passed into the function.
//
unsigned ArgNo = 0;
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I, ++ArgNo) {
// Each argument passed in has a cost at both the caller and the callee
// sides. This favors functions that take many arguments over functions
// that take few arguments.
InlineCost -= 20;
// If this is a function being passed in, it is very likely that we will be
// able to turn an indirect function call into a direct function call.
if (isa<Function>(I))
InlineCost -= 100;
// If an alloca is passed in, inlining this function is likely to allow
// significant future optimization possibilities (like scalar promotion, and
// scalarization), so encourage the inlining of the function.
//
else if (isa<AllocaInst>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].AllocaWeight;
// If this is a constant being passed into the function, use the argument
// weights calculated for the callee to determine how much will be folded
// away with this information.
} else if (isa<Constant>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].ConstantWeight;
}
}
// Now that we have considered all of the factors that make the call site more
// likely to be inlined, look at factors that make us not want to inline it.
// Don't inline into something too big, which would make it bigger. Here, we
// count each basic block as a single unit.
//
InlineCost += Caller->size()/20;
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 5.
InlineCost += CalleeFI.NumInsts*5 + CalleeFI.NumBlocks*20;
return InlineCost;
}
// doInitialization - Initializes the vector of functions that have been
// annotated with the noinline attribute.
bool SimpleInliner::doInitialization(CallGraph &CG) {
@@ -321,3 +80,4 @@ bool SimpleInliner::doInitialization(CallGraph &CG) {
return false;
}