1 //===- ReplayInlineAdvisor.cpp - Replay InlineAdvisor ---------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements ReplayInlineAdvisor that replays inline decisions based
10 // on previous inline remarks from optimization remark log. This is a best
11 // effort approach useful for testing compiler/source changes while holding
12 // inlining steady.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/Analysis/ReplayInlineAdvisor.h"
17 #include "llvm/IR/DebugInfoMetadata.h"
18 #include "llvm/IR/Instructions.h"
19 #include "llvm/Support/LineIterator.h"
20 
21 using namespace llvm;
22 
23 #define DEBUG_TYPE "inline-replay"
24 
25 ReplayInlineAdvisor::ReplayInlineAdvisor(
26     Module &M, FunctionAnalysisManager &FAM, LLVMContext &Context,
27     std::unique_ptr<InlineAdvisor> OriginalAdvisor, StringRef RemarksFile,
28     bool EmitRemarks)
29     : InlineAdvisor(M, FAM), OriginalAdvisor(std::move(OriginalAdvisor)),
30       HasReplayRemarks(false), EmitRemarks(EmitRemarks) {
31   auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(RemarksFile);
32   std::error_code EC = BufferOrErr.getError();
33   if (EC) {
34     Context.emitError("Could not open remarks file: " + EC.message());
35     return;
36   }
37 
38   // Example for inline remarks to parse:
39   //   main:3:1.1: '_Z3subii' inlined into 'main' at callsite sum:1 @ main:3:1.1
40   // We use the callsite string after `at callsite` to replay inlining.
41   line_iterator LineIt(*BufferOrErr.get(), /*SkipBlanks=*/true);
42   for (; !LineIt.is_at_eof(); ++LineIt) {
43     StringRef Line = *LineIt;
44     auto Pair = Line.split(" at callsite ");
45 
46     StringRef Callee = Pair.first.split(" inlined into")
47                            .first.rsplit(": '")
48                            .second.drop_back();
49     auto CallSite = Pair.second.split(";").first;
50 
51     if (Callee.empty() || CallSite.empty())
52       continue;
53 
54     std::string Combined = (Callee + CallSite).str();
55     InlineSitesFromRemarks.insert(Combined);
56   }
57 
58   HasReplayRemarks = true;
59 }
60 
61 std::unique_ptr<InlineAdvice> ReplayInlineAdvisor::getAdviceImpl(CallBase &CB) {
62   assert(HasReplayRemarks);
63 
64   Function &Caller = *CB.getCaller();
65   auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(Caller);
66 
67   if (InlineSitesFromRemarks.empty())
68     return std::make_unique<DefaultInlineAdvice>(this, CB, None, ORE,
69                                                  EmitRemarks);
70 
71   std::string CallSiteLoc = getCallSiteLocation(CB.getDebugLoc());
72   StringRef Callee = CB.getCalledFunction()->getName();
73   std::string Combined = (Callee + CallSiteLoc).str();
74   auto Iter = InlineSitesFromRemarks.find(Combined);
75 
76   Optional<InlineCost> InlineRecommended = None;
77   if (Iter != InlineSitesFromRemarks.end()) {
78     InlineRecommended = llvm::InlineCost::getAlways("found in replay");
79   }
80 
81   return std::make_unique<DefaultInlineAdvice>(this, CB, InlineRecommended, ORE,
82                                                EmitRemarks);
83 }
84