[llvm-cov] Add a cl::opt to control the number of threads
When an output directory is specified, llvm-cov spawns some threads to
speed up the process of writing out file reports. Add an option which
allows users to control how many threads llvm-cov uses.
A CommandGuide.rst update + test is included.
llvm-svn: 307609
diff --git a/llvm/tools/llvm-cov/CodeCoverage.cpp b/llvm/tools/llvm-cov/CodeCoverage.cpp
index 6179c76..3cbd659 100644
--- a/llvm/tools/llvm-cov/CodeCoverage.cpp
+++ b/llvm/tools/llvm-cov/CodeCoverage.cpp
@@ -32,6 +32,7 @@
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/Threading.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Support/ToolOutputFile.h"
#include <functional>
@@ -705,6 +706,12 @@
"project-title", cl::Optional,
cl::desc("Set project title for the coverage report"));
+ cl::opt<unsigned> NumThreads(
+ "num-threads", cl::init(0),
+ cl::desc("Number of merge threads to use (default: autodetect)"));
+ cl::alias NumThreadsA("j", cl::desc("Alias for --num-threads"),
+ cl::aliasopt(NumThreads));
+
auto Err = commandLineParser(argc, argv);
if (Err)
return Err;
@@ -790,15 +797,19 @@
}
}
- // FIXME: Sink the hardware_concurrency() == 1 check into ThreadPool.
- if (!ViewOpts.hasOutputDirectory() ||
- std::thread::hardware_concurrency() == 1) {
+ // If NumThreads is not specified, auto-detect a good default.
+ if (NumThreads == 0)
+ NumThreads =
+ std::max(1U, std::min(llvm::heavyweight_hardware_concurrency(),
+ unsigned(SourceFiles.size())));
+
+ if (!ViewOpts.hasOutputDirectory() || NumThreads == 1) {
for (const std::string &SourceFile : SourceFiles)
writeSourceFileView(SourceFile, Coverage.get(), Printer.get(),
ShowFilenames);
} else {
// In -output-dir mode, it's safe to use multiple threads to print files.
- ThreadPool Pool;
+ ThreadPool Pool(NumThreads);
for (const std::string &SourceFile : SourceFiles)
Pool.async(&CodeCoverageTool::writeSourceFileView, this, SourceFile,
Coverage.get(), Printer.get(), ShowFilenames);