1 //===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a custom inliner that handles only functions that
11 // are marked as "always inline".
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/IPO.h"
16 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/Analysis/AssumptionCache.h"
18 #include "llvm/Analysis/CallGraph.h"
19 #include "llvm/Analysis/InlineCost.h"
20 #include "llvm/Analysis/TargetLibraryInfo.h"
21 #include "llvm/IR/CallSite.h"
22 #include "llvm/IR/CallingConv.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/IR/Type.h"
28 #include "llvm/Transforms/IPO/InlinerPass.h"
32 #define DEBUG_TYPE "inline"
36 /// \brief Inliner pass which only handles "always inline" functions.
37 class AlwaysInliner : public Inliner {
40 // Use extremely low threshold.
41 AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true) {
42 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
45 AlwaysInliner(bool InsertLifetime)
46 : Inliner(ID, -2000000000, InsertLifetime) {
47 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
50 static char ID; // Pass identification, replacement for typeid
52 InlineCost getInlineCost(CallSite CS) override;
54 using llvm::Pass::doFinalization;
55 bool doFinalization(CallGraph &CG) override {
56 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
62 char AlwaysInliner::ID = 0;
63 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
64 "Inliner for always_inline functions", false, false)
65 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
66 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
67 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
68 INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
69 "Inliner for always_inline functions", false, false)
71 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
73 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
74 return new AlwaysInliner(InsertLifetime);
77 /// \brief Get the inline cost for the always-inliner.
79 /// The always inliner *only* handles functions which are marked with the
80 /// attribute to force inlining. As such, it is dramatically simpler and avoids
81 /// using the powerful (but expensive) inline cost analysis. Instead it uses
82 /// a very simple and boring direct walk of the instructions looking for
83 /// impossible-to-inline constructs.
85 /// Note, it would be possible to go to some lengths to cache the information
86 /// computed here, but as we only expect to do this for relatively few and
87 /// small functions which have the explicit attribute to force inlining, it is
88 /// likely not worth it in practice.
89 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
90 Function *Callee = CS.getCalledFunction();
92 // Only inline direct calls to functions with always-inline attributes
93 // that are viable for inlining. FIXME: We shouldn't even get here for
95 if (Callee && !Callee->isDeclaration() &&
96 CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee))
97 return InlineCost::getAlways();
99 return InlineCost::getNever();