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//===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a custom inliner that handles only functions that
// are marked as "always inline".
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/Transforms/IPO/InlinerPass.h"
using namespace llvm;
#define DEBUG_TYPE "inline"
namespace {
/// \brief Inliner pass which only handles "always inline" functions.
class AlwaysInliner : public Inliner {
InlineCostAnalysis *ICA;
public:
// Use extremely low threshold.
AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true),
ICA(nullptr) {
initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
}
AlwaysInliner(bool InsertLifetime)
: Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) {
initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
}
static char ID; // Pass identification, replacement for typeid
InlineCost getInlineCost(CallSite CS) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
bool runOnSCC(CallGraphSCC &SCC) override;
using llvm::Pass::doFinalization;
bool doFinalization(CallGraph &CG) override {
return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
}
};
}
char AlwaysInliner::ID = 0;
INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
"Inliner for always_inline functions", false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis)
INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
"Inliner for always_inline functions", false, false)
Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
return new AlwaysInliner(InsertLifetime);
}
/// \brief Get the inline cost for the always-inliner.
///
/// The always inliner *only* handles functions which are marked with the
/// attribute to force inlining. As such, it is dramatically simpler and avoids
/// using the powerful (but expensive) inline cost analysis. Instead it uses
/// a very simple and boring direct walk of the instructions looking for
/// impossible-to-inline constructs.
///
/// Note, it would be possible to go to some lengths to cache the information
/// computed here, but as we only expect to do this for relatively few and
/// small functions which have the explicit attribute to force inlining, it is
/// likely not worth it in practice.
InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
Function *Callee = CS.getCalledFunction();
// Only inline direct calls to functions with always-inline attributes
// that are viable for inlining. FIXME: We shouldn't even get here for
// declarations.
if (Callee && !Callee->isDeclaration() &&
CS.hasFnAttr(Attribute::AlwaysInline) &&
ICA->isInlineViable(*Callee))
return InlineCost::getAlways();
return InlineCost::getNever();
}
bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) {
ICA = &getAnalysis<InlineCostAnalysis>();
return Inliner::runOnSCC(SCC);
}
void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<InlineCostAnalysis>();
Inliner::getAnalysisUsage(AU);
}
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