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This change leverages the work done in D83743 to replay in the SampleProfile inliner to also be used in the CGSCC inliner. NOTE: currently restricted to non-ML advisors only. The added switch `-cgscc-inline-replay=<remarks file>` will replay the inlining decisions in that file where the remarks file is generated via `-Rpass=inline`. The aim here is to make it easier to analyze changes that would modify inlining heuristics to be separated from this behavior. Doing so allows easier examination of assembly and runtime behavior compared to the baseline rather than trying to dig through the large churn caused by inlining. In LTO compilation, since inlining is done twice you can separately specify replay by passing the flag to the FE (`-cgscc-inline-replay=`) and to the linker (`-Wl,cgscc-inline-replay=`) with the remarks generated from their respective places. Testing on mysqld by comparing the inline decisions between base (generates remarks.txt) and diff (replay using identical input/tools with remarks.txt) and examining the inlining sites with `diff` shows 14,000 mismatches out of 247,341 for a ~94% replay accuracy. I believe this gap can be narrowed further though for the general case we may never achieve full accuracy. For my personal use, this is close enough to be representative: I set the baseline as the one generated by the replay on identical input/toolset and compare that to my modified input/toolset using the same replay. Testing: ninja check-llvm newly added test correctly replays CGSCC inlining decisions Reviewed By: mtrofin, wenlei Differential Revision: https://reviews.llvm.org/D94334
83 lines
3.0 KiB
C++
83 lines
3.0 KiB
C++
//===- ReplayInlineAdvisor.cpp - Replay InlineAdvisor ---------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements ReplayInlineAdvisor that replays inline decisions based
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// on previous inline remarks from optimization remark log. This is a best
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// effort approach useful for testing compiler/source changes while holding
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// inlining steady.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/ReplayInlineAdvisor.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Support/LineIterator.h"
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using namespace llvm;
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#define DEBUG_TYPE "inline-replay"
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ReplayInlineAdvisor::ReplayInlineAdvisor(
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Module &M, FunctionAnalysisManager &FAM, LLVMContext &Context,
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std::unique_ptr<InlineAdvisor> OriginalAdvisor, StringRef RemarksFile,
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bool EmitRemarks)
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: InlineAdvisor(M, FAM), OriginalAdvisor(std::move(OriginalAdvisor)),
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HasReplayRemarks(false), EmitRemarks(EmitRemarks) {
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auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(RemarksFile);
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std::error_code EC = BufferOrErr.getError();
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if (EC) {
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Context.emitError("Could not open remarks file: " + EC.message());
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return;
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}
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// Example for inline remarks to parse:
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// main:3:1.1: _Z3subii inlined into main at callsite sum:1 @ main:3:1.1
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// We use the callsite string after `at callsite` to replay inlining.
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line_iterator LineIt(*BufferOrErr.get(), /*SkipBlanks=*/true);
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for (; !LineIt.is_at_eof(); ++LineIt) {
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StringRef Line = *LineIt;
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auto Pair = Line.split(" at callsite ");
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auto Callee = Pair.first.split(" inlined into").first.rsplit(": ").second;
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auto CallSite = Pair.second.split(";").first;
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if (Callee.empty() || CallSite.empty())
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continue;
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std::string Combined = (Callee + CallSite).str();
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InlineSitesFromRemarks.insert(Combined);
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}
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HasReplayRemarks = true;
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}
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std::unique_ptr<InlineAdvice> ReplayInlineAdvisor::getAdviceImpl(CallBase &CB) {
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assert(HasReplayRemarks);
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Function &Caller = *CB.getCaller();
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auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(Caller);
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if (InlineSitesFromRemarks.empty())
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return std::make_unique<DefaultInlineAdvice>(this, CB, None, ORE,
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EmitRemarks);
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std::string CallSiteLoc = getCallSiteLocation(CB.getDebugLoc());
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StringRef Callee = CB.getCalledFunction()->getName();
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std::string Combined = (Callee + CallSiteLoc).str();
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auto Iter = InlineSitesFromRemarks.find(Combined);
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Optional<InlineCost> InlineRecommended = None;
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if (Iter != InlineSitesFromRemarks.end()) {
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InlineRecommended = llvm::InlineCost::getAlways("found in replay");
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}
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return std::make_unique<DefaultInlineAdvice>(this, CB, InlineRecommended, ORE,
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EmitRemarks);
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}
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