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//===- Inliner.cpp - Code common to all inliners --------------------------===//
//
// 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 file implements the mechanics required to implement inlining without
// missing any calls and updating the call graph. The decisions of which calls
// are profitable to inline are implemented elsewhere.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "inline"
#include "Inliner.h"
#include "llvm/Module.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include <set>
using namespace llvm;
STATISTIC(NumInlined, "Number of functions inlined");
STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
namespace {
cl::opt<unsigned> // FIXME: 200 is VERY conservative
InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
cl::desc("Control the amount of inlining to perform (default = 200)"));
}
const char Inliner::ID = 0;
Inliner::Inliner()
: CallGraphSCCPass((intptr_t)&ID), InlineThreshold(InlineLimit) {}
/// getAnalysisUsage - For this class, we declare that we require and preserve
/// the call graph. If the derived class implements this method, it should
/// always explicitly call the implementation here.
void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
Info.addRequired<TargetData>();
CallGraphSCCPass::getAnalysisUsage(Info);
}
// InlineCallIfPossible - If it is possible to inline the specified call site,
// do so and update the CallGraph for this operation.
static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
const std::set<Function*> &SCCFunctions,
const TargetData &TD) {
Function *Callee = CS.getCalledFunction();
if (!InlineFunction(CS, &CG, &TD)) return false;
// If we inlined the last possible call site to the function, delete the
// function body now.
if (Callee->use_empty() && Callee->hasInternalLinkage() &&
!SCCFunctions.count(Callee)) {
DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
// Remove any call graph edges from the callee to its callees.
CallGraphNode *CalleeNode = CG[Callee];
while (CalleeNode->begin() != CalleeNode->end())
CalleeNode->removeCallEdgeTo((CalleeNode->end()-1)->second);
// Removing the node for callee from the call graph and delete it.
delete CG.removeFunctionFromModule(CalleeNode);
++NumDeleted;
}
return true;
}
bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
CallGraph &CG = getAnalysis<CallGraph>();
std::set<Function*> SCCFunctions;
DOUT << "Inliner visiting SCC:";
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
Function *F = SCC[i]->getFunction();
if (F) SCCFunctions.insert(F);
DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
}
// Scan through and identify all call sites ahead of time so that we only
// inline call sites in the original functions, not call sites that result
// from inlining other functions.
std::vector<CallSite> CallSites;
for (unsigned i = 0, e = SCC.size(); i != e; ++i)
if (Function *F = SCC[i]->getFunction())
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
CallSite CS = CallSite::get(I);
if (CS.getInstruction() && (!CS.getCalledFunction() ||
!CS.getCalledFunction()->isDeclaration()))
CallSites.push_back(CS);
}
DOUT << ": " << CallSites.size() << " call sites.\n";
// Now that we have all of the call sites, move the ones to functions in the
// current SCC to the end of the list.
unsigned FirstCallInSCC = CallSites.size();
for (unsigned i = 0; i < FirstCallInSCC; ++i)
if (Function *F = CallSites[i].getCalledFunction())
if (SCCFunctions.count(F))
std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
// Now that we have all of the call sites, loop over them and inline them if
// it looks profitable to do so.
bool Changed = false;
bool LocalChange;
do {
LocalChange = false;
// Iterate over the outer loop because inlining functions can cause indirect
// calls to become direct calls.
for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
if (Function *Callee = CallSites[CSi].getCalledFunction()) {
// Calls to external functions are never inlinable.
if (Callee->isDeclaration() ||
CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
if (SCC.size() == 1) {
std::swap(CallSites[CSi], CallSites.back());
CallSites.pop_back();
} else {
// Keep the 'in SCC / not in SCC' boundary correct.
CallSites.erase(CallSites.begin()+CSi);
}
--CSi;
continue;
}
// If the policy determines that we should inline this function,
// try to do so.
CallSite CS = CallSites[CSi];
int InlineCost = getInlineCost(CS);
if (InlineCost >= (int)InlineThreshold) {
DOUT << " NOT Inlining: cost=" << InlineCost
<< ", Call: " << *CS.getInstruction();
} else {
DOUT << " Inlining: cost=" << InlineCost
<< ", Call: " << *CS.getInstruction();
// Attempt to inline the function...
if (InlineCallIfPossible(CS, CG, SCCFunctions,
getAnalysis<TargetData>())) {
// Remove this call site from the list. If possible, use
// swap/pop_back for efficiency, but do not use it if doing so would
// move a call site to a function in this SCC before the
// 'FirstCallInSCC' barrier.
if (SCC.size() == 1) {
std::swap(CallSites[CSi], CallSites.back());
CallSites.pop_back();
} else {
CallSites.erase(CallSites.begin()+CSi);
}
--CSi;
++NumInlined;
Changed = true;
LocalChange = true;
}
}
}
} while (LocalChange);
return Changed;
}
// doFinalization - Remove now-dead linkonce functions at the end of
// processing to avoid breaking the SCC traversal.
bool Inliner::doFinalization(CallGraph &CG) {
std::set<CallGraphNode*> FunctionsToRemove;
// Scan for all of the functions, looking for ones that should now be removed
// from the program. Insert the dead ones in the FunctionsToRemove set.
for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
CallGraphNode *CGN = I->second;
if (Function *F = CGN ? CGN->getFunction() : 0) {
// If the only remaining users of the function are dead constants, remove
// them.
F->removeDeadConstantUsers();
if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
F->use_empty()) {
// Remove any call graph edges from the function to its callees.
while (CGN->begin() != CGN->end())
CGN->removeCallEdgeTo((CGN->end()-1)->second);
// Remove any edges from the external node to the function's call graph
// node. These edges might have been made irrelegant due to
// optimization of the program.
CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
// Removing the node for callee from the call graph and delete it.
FunctionsToRemove.insert(CGN);
}
}
}
// Now that we know which functions to delete, do so. We didn't want to do
// this inline, because that would invalidate our CallGraph::iterator
// objects. :(
bool Changed = false;
for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
E = FunctionsToRemove.end(); I != E; ++I) {
delete CG.removeFunctionFromModule(*I);
++NumDeleted;
Changed = true;
}
return Changed;
}
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