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We use the enums to query whether an Attributes object has that attribute. The opaque layer is responsible for knowing where that specific attribute is stored. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165488 91177308-0d34-0410-b5e6-96231b3b80d8
133 lines
4.7 KiB
C++
133 lines
4.7 KiB
C++
//===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a custom inliner that handles only functions that
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// are marked as "always inline".
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "inline"
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#include "llvm/CallingConv.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Module.h"
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#include "llvm/Type.h"
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Analysis/InlineCost.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Transforms/IPO/InlinerPass.h"
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#include "llvm/DataLayout.h"
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#include "llvm/ADT/SmallPtrSet.h"
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using namespace llvm;
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namespace {
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// AlwaysInliner only inlines functions that are mark as "always inline".
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class AlwaysInliner : public Inliner {
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public:
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// Use extremely low threshold.
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AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/true) {
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initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
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}
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AlwaysInliner(bool InsertLifetime) : Inliner(ID, -2000000000,
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InsertLifetime) {
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initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
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}
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static char ID; // Pass identification, replacement for typeid
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virtual InlineCost getInlineCost(CallSite CS);
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virtual bool doFinalization(CallGraph &CG) {
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return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/true);
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}
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virtual bool doInitialization(CallGraph &CG);
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};
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}
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char AlwaysInliner::ID = 0;
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INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
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"Inliner for always_inline functions", false, false)
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INITIALIZE_AG_DEPENDENCY(CallGraph)
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INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
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"Inliner for always_inline functions", false, false)
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Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
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Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
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return new AlwaysInliner(InsertLifetime);
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}
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/// \brief Minimal filter to detect invalid constructs for inlining.
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static bool isInlineViable(Function &F) {
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bool ReturnsTwice =F.getFnAttributes().hasAttribute(Attributes::ReturnsTwice);
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for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
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// Disallow inlining of functions which contain an indirect branch.
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if (isa<IndirectBrInst>(BI->getTerminator()))
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return false;
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for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
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++II) {
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CallSite CS(II);
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if (!CS)
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continue;
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// Disallow recursive calls.
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if (&F == CS.getCalledFunction())
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return false;
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// Disallow calls which expose returns-twice to a function not previously
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// attributed as such.
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if (!ReturnsTwice && CS.isCall() &&
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cast<CallInst>(CS.getInstruction())->canReturnTwice())
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return false;
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}
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}
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return true;
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}
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/// \brief Get the inline cost for the always-inliner.
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///
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/// The always inliner *only* handles functions which are marked with the
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/// attribute to force inlining. As such, it is dramatically simpler and avoids
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/// using the powerful (but expensive) inline cost analysis. Instead it uses
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/// a very simple and boring direct walk of the instructions looking for
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/// impossible-to-inline constructs.
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///
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/// Note, it would be possible to go to some lengths to cache the information
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/// computed here, but as we only expect to do this for relatively few and
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/// small functions which have the explicit attribute to force inlining, it is
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/// likely not worth it in practice.
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InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
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Function *Callee = CS.getCalledFunction();
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// We assume indirect calls aren't calling an always-inline function.
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if (!Callee) return InlineCost::getNever();
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// We can't inline calls to external functions.
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// FIXME: We shouldn't even get here.
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if (Callee->isDeclaration()) return InlineCost::getNever();
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// Return never for anything not marked as always inline.
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if (!Callee->getFnAttributes().hasAttribute(Attributes::AlwaysInline))
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return InlineCost::getNever();
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// Do some minimal analysis to preclude non-viable functions.
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if (!isInlineViable(*Callee))
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return InlineCost::getNever();
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// Otherwise, force inlining.
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return InlineCost::getAlways();
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}
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// doInitialization - Initializes the vector of functions that have not
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// been annotated with the "always inline" attribute.
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bool AlwaysInliner::doInitialization(CallGraph &CG) {
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return false;
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}
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