133 lines
4.7 KiB
C++
133 lines
4.7 KiB
C++
//===- 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".
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "inline"
|
|
#include "llvm/CallingConv.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/IntrinsicInst.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/Type.h"
|
|
#include "llvm/Analysis/CallGraph.h"
|
|
#include "llvm/Analysis/InlineCost.h"
|
|
#include "llvm/Support/CallSite.h"
|
|
#include "llvm/Transforms/IPO.h"
|
|
#include "llvm/Transforms/IPO/InlinerPass.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
|
|
// AlwaysInliner only inlines functions that are mark as "always inline".
|
|
class AlwaysInliner : public Inliner {
|
|
public:
|
|
// Use extremely low threshold.
|
|
AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/true) {
|
|
initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
AlwaysInliner(bool InsertLifetime) : Inliner(ID, -2000000000,
|
|
InsertLifetime) {
|
|
initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
static char ID; // Pass identification, replacement for typeid
|
|
virtual InlineCost getInlineCost(CallSite CS);
|
|
virtual bool doFinalization(CallGraph &CG) {
|
|
return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/true);
|
|
}
|
|
virtual bool doInitialization(CallGraph &CG);
|
|
};
|
|
}
|
|
|
|
char AlwaysInliner::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
|
|
"Inliner for always_inline functions", false, false)
|
|
INITIALIZE_AG_DEPENDENCY(CallGraph)
|
|
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 Minimal filter to detect invalid constructs for inlining.
|
|
static bool isInlineViable(Function &F) {
|
|
bool ReturnsTwice = F.hasFnAttr(Attribute::ReturnsTwice);
|
|
for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
|
|
// Disallow inlining of functions which contain an indirect branch.
|
|
if (isa<IndirectBrInst>(BI->getTerminator()))
|
|
return false;
|
|
|
|
for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
|
|
++II) {
|
|
CallSite CS(II);
|
|
if (!CS)
|
|
continue;
|
|
|
|
// Disallow recursive calls.
|
|
if (&F == CS.getCalledFunction())
|
|
return false;
|
|
|
|
// Disallow calls which expose returns-twice to a function not previously
|
|
// attributed as such.
|
|
if (!ReturnsTwice && CS.isCall() &&
|
|
cast<CallInst>(CS.getInstruction())->canReturnTwice())
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// \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();
|
|
// We assume indirect calls aren't calling an always-inline function.
|
|
if (!Callee) return InlineCost::getNever();
|
|
|
|
// We can't inline calls to external functions.
|
|
// FIXME: We shouldn't even get here.
|
|
if (Callee->isDeclaration()) return InlineCost::getNever();
|
|
|
|
// Return never for anything not marked as always inline.
|
|
if (!Callee->hasFnAttr(Attribute::AlwaysInline))
|
|
return InlineCost::getNever();
|
|
|
|
// Do some minimal analysis to preclude non-viable functions.
|
|
if (!isInlineViable(*Callee))
|
|
return InlineCost::getNever();
|
|
|
|
// Otherwise, force inlining.
|
|
return InlineCost::getAlways();
|
|
}
|
|
|
|
// doInitialization - Initializes the vector of functions that have not
|
|
// been annotated with the "always inline" attribute.
|
|
bool AlwaysInliner::doInitialization(CallGraph &CG) {
|
|
return false;
|
|
}
|