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a7a66b3792
Summary: Prototype of a JIT compiler that utilizes ThinLTO summaries to compile modules ahead of time. This is an implementation of the concept I presented in my "ThinLTO Summaries in JIT Compilation" talk at the 2018 Developers' Meeting: http://llvm.org/devmtg/2018-10/talk-abstracts.html#lt8 Upfront the JIT first populates the *combined ThinLTO module index*, which provides fast access to the global call-graph and module paths by function. Next, it loads the main function's module and compiles it. All functions in the module will be emitted with prolog instructions that *fire a discovery flag* once execution reaches them. In parallel, the *discovery thread* is busy-watching the existing flags. Once it detects one has fired, it uses the module index to find all functions that are reachable from it within a given number of calls and submits their defining modules to the compilation pipeline. While execution continues, more flags are fired and further modules added. Ideally the JIT can be tuned in a way, so that in the majority of cases the code on the execution path can be compiled ahead of time. In cases where it doesn't work, the JIT has a *definition generator* in place that loads modules if missing functions are reached. Reviewers: lhames, dblaikie, jfb, tejohnson, pree-jackie, AlexDenisov, kavon Subscribers: mgorny, mehdi_amini, inglorion, hiraditya, steven_wu, dexonsmith, arphaman, jfb, merge_guards_bot, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D72486
84 lines
3.2 KiB
C++
84 lines
3.2 KiB
C++
#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Error.h"
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#include "llvm/Support/InitLLVM.h"
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#include "llvm/Support/TargetSelect.h"
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#include "ThinLtoJIT.h"
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#include <string>
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#include <vector>
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using namespace llvm;
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static cl::list<std::string>
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InputFiles(cl::Positional, cl::OneOrMore,
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cl::desc("<bitcode files or global index>"));
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static cl::list<std::string> InputArgs("args", cl::Positional,
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cl::desc("<program arguments>..."),
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cl::ZeroOrMore, cl::PositionalEatsArgs);
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static cl::opt<unsigned> CompileThreads("compile-threads", cl::Optional,
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cl::desc("Number of compile threads"),
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cl::init(4));
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static cl::opt<unsigned> LoadThreads("load-threads", cl::Optional,
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cl::desc("Number of module load threads"),
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cl::init(8));
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static cl::opt<unsigned>
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LookaheadLevels("lookahead", cl::Optional,
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cl::desc("Calls to look ahead of execution"), cl::init(4));
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static cl::opt<unsigned> DiscoveryFlagsBucketSize(
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"discovery-flag-bucket-size", cl::Optional,
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cl::desc("Flags per bucket (rounds up to memory pages)"), cl::init(4096));
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static cl::opt<orc::ThinLtoJIT::ExplicitMemoryBarrier>
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MemFence("mem-fence",
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cl::desc("Control memory fences for cache synchronization"),
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cl::init(orc::ThinLtoJIT::NeverFence),
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cl::values(clEnumValN(orc::ThinLtoJIT::NeverFence, "never",
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"No use of memory fences"),
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clEnumValN(orc::ThinLtoJIT::FenceStaticCode, "static",
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"Use of memory fences in static code only"),
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clEnumValN(orc::ThinLtoJIT::FenceJITedCode, "jited",
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"Install memory fences in JITed code only"),
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clEnumValN(orc::ThinLtoJIT::AlwaysFence, "always",
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"Always use of memory fences")));
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static cl::opt<bool>
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AllowNudge("allow-nudge",
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cl::desc("Allow the symbol generator to nudge symbols into "
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"discovery even though they haven't been reached"),
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cl::init(false));
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static cl::opt<bool> PrintStats("print-stats",
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cl::desc("Print module stats on shutdown"),
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cl::init(false));
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int main(int argc, char *argv[]) {
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InitLLVM X(argc, argv);
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InitializeNativeTarget();
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InitializeNativeTargetAsmPrinter();
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cl::ParseCommandLineOptions(argc, argv, "ThinLtoJIT");
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Error Err = Error::success();
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auto atLeastOne = [](unsigned N) { return std::max(1u, N); };
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orc::ThinLtoJIT Jit(InputFiles, "main", atLeastOne(LookaheadLevels),
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atLeastOne(CompileThreads), atLeastOne(LoadThreads),
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DiscoveryFlagsBucketSize, MemFence, AllowNudge,
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PrintStats, Err);
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if (Err) {
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logAllUnhandledErrors(std::move(Err), errs(), "[ThinLtoJIT] ");
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exit(1);
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}
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ExitOnError ExitOnErr;
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ExitOnErr.setBanner("[ThinLtoJIT] ");
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return ExitOnErr(Jit.main(InputArgs));
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}
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