1 //===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements a custom inliner that handles only functions that
11 // are marked as "always inline".
12 //
13 //===----------------------------------------------------------------------===//
14
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/ProfileSummaryInfo.h"
21 #include "llvm/Analysis/TargetLibraryInfo.h"
22 #include "llvm/IR/CallSite.h"
23 #include "llvm/IR/CallingConv.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/Type.h"
29 #include "llvm/Transforms/IPO/InlinerPass.h"
30
31 using namespace llvm;
32
33 #define DEBUG_TYPE "inline"
34
35 namespace {
36
37 /// \brief Inliner pass which only handles "always inline" functions.
38 class AlwaysInliner : public Inliner {
39
40 public:
AlwaysInliner()41 AlwaysInliner() : Inliner(ID, /*InsertLifetime*/ true) {
42 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
43 }
44
AlwaysInliner(bool InsertLifetime)45 AlwaysInliner(bool InsertLifetime) : Inliner(ID, InsertLifetime) {
46 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
47 }
48
49 /// Main run interface method. We override here to avoid calling skipSCC().
runOnSCC(CallGraphSCC & SCC)50 bool runOnSCC(CallGraphSCC &SCC) override { return inlineCalls(SCC); }
51
52 static char ID; // Pass identification, replacement for typeid
53
54 InlineCost getInlineCost(CallSite CS) override;
55
56 using llvm::Pass::doFinalization;
doFinalization(CallGraph & CG)57 bool doFinalization(CallGraph &CG) override {
58 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
59 }
60 };
61
62 }
63
64 char AlwaysInliner::ID = 0;
65 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
66 "Inliner for always_inline functions", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)67 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
68 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
69 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
70 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
71 INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
72 "Inliner for always_inline functions", false, false)
73
74 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
75
createAlwaysInlinerPass(bool InsertLifetime)76 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
77 return new AlwaysInliner(InsertLifetime);
78 }
79
80 /// \brief Get the inline cost for the always-inliner.
81 ///
82 /// The always inliner *only* handles functions which are marked with the
83 /// attribute to force inlining. As such, it is dramatically simpler and avoids
84 /// using the powerful (but expensive) inline cost analysis. Instead it uses
85 /// a very simple and boring direct walk of the instructions looking for
86 /// impossible-to-inline constructs.
87 ///
88 /// Note, it would be possible to go to some lengths to cache the information
89 /// computed here, but as we only expect to do this for relatively few and
90 /// small functions which have the explicit attribute to force inlining, it is
91 /// likely not worth it in practice.
getInlineCost(CallSite CS)92 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
93 Function *Callee = CS.getCalledFunction();
94
95 // Only inline direct calls to functions with always-inline attributes
96 // that are viable for inlining. FIXME: We shouldn't even get here for
97 // declarations.
98 if (Callee && !Callee->isDeclaration() &&
99 CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee))
100 return InlineCost::getAlways();
101
102 return InlineCost::getNever();
103 }
104