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llvm: Add support for collecting time trace (#8546)

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LLVM time profiler can collect time traces and present them in a
hierarchical view. Which breakdowns the time spent in each Pass or even
IR unit. The result is also exported into a format that can be easily
visualized by the Chrome browser.

Currently this features is controlled by the following environment
variables:
 - `ZIG_LLVM_TIME_TRACE_FILE` toggles this feature and specifies the
   output time trace file.
 - `ZIG_LLVM_TIME_TRACE_GRANULARITY` controls the time granularity in
   ms (default to 500).
This commit is contained in:
Min-Yih Hsu
2021-06-04 00:32:37 -07:00
committed by GitHub
parent 9c08a33b22
commit 83e0a49ba4
1 changed files with 45 additions and 2 deletions
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47
src/zig_llvm.cpp
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@@ -46,7 +46,9 @@
#include <llvm/Support/CommandLine.h>
#include <llvm/Support/Host.h>
#include <llvm/Support/FileSystem.h>
#include <llvm/Support/Process.h>
#include <llvm/Support/TargetParser.h>
#include <llvm/Support/TimeProfiler.h>
#include <llvm/Support/Timer.h>
#include <llvm/Support/raw_ostream.h>
#include <llvm/Support/TargetRegistry.h>
@@ -187,13 +189,48 @@ unsigned ZigLLVMDataLayoutGetProgramAddressSpace(LLVMTargetDataRef TD) {
return unwrap(TD)->getProgramAddressSpace();
}
namespace {
// LLVM's time profiler can provide a hierarchy view of the time spent
// in each component. It generates JSON report in Chrome's "Trace Event"
// format. So the report can be easily visualized by the Chrome browser.
struct TimeTracerRAII {
// Granularity in ms
unsigned TimeTraceGranularity;
StringRef TimeTraceFile, OutputFilename;
bool EnableTimeTrace;
TimeTracerRAII(StringRef ProgramName, StringRef OF)
: TimeTraceGranularity(500U),
TimeTraceFile(std::getenv("ZIG_LLVM_TIME_TRACE_FILE")),
OutputFilename(OF),
EnableTimeTrace(!TimeTraceFile.empty()) {
if (EnableTimeTrace) {
if (const char *G = std::getenv("ZIG_LLVM_TIME_TRACE_GRANULARITY"))
TimeTraceGranularity = (unsigned)std::atoi(G);
llvm::timeTraceProfilerInitialize(TimeTraceGranularity, ProgramName);
}
}
~TimeTracerRAII() {
if (EnableTimeTrace) {
if (auto E = llvm::timeTraceProfilerWrite(TimeTraceFile, OutputFilename)) {
handleAllErrors(std::move(E), [&](const StringError &SE) {
errs() << SE.getMessage() << "\n";
});
return;
}
timeTraceProfilerCleanup();
}
}
};
} // end anonymous namespace
bool ZigLLVMTargetMachineEmitToFile(LLVMTargetMachineRef targ_machine_ref, LLVMModuleRef module_ref,
char **error_message, bool is_debug,
bool is_small, bool time_report, bool tsan, bool lto,
const char *asm_filename, const char *bin_filename, const char *llvm_ir_filename)
{
// TODO: Maybe we should collect time trace rather than using timer
// to get a more hierarchical timeline view
TimePassesIsEnabled = time_report;
raw_fd_ostream *dest_asm_ptr = nullptr;
@@ -219,6 +256,12 @@ bool ZigLLVMTargetMachineEmitToFile(LLVMTargetMachineRef targ_machine_ref, LLVMM
std::unique_ptr<raw_fd_ostream> dest_asm(dest_asm_ptr),
dest_bin(dest_bin_ptr);
auto PID = sys::Process::getProcessId();
std::string ProcName = "zig-";
ProcName += std::to_string(PID);
TimeTracerRAII TimeTracer(ProcName,
bin_filename? bin_filename : asm_filename);
TargetMachine &target_machine = *reinterpret_cast<TargetMachine*>(targ_machine_ref);
target_machine.setO0WantsFastISel(true);