[PATCH] D39355: [dsymutil] Implement the --threads option

[Jonas Devlieghere via Phabricator via llvm-commits]

JDevlieghere created this revision.

This patch adds the --threads option to dsymutil to process architectures in parallel. The feature is already present in the version distributed with Xcode, but was not yet upstreamed.

This is NFC as far as the linking behavior is concerned. As threads are used automatically, the current tests cover the change in implementation.


Repository:
  rL LLVM

https://reviews.llvm.org/D39355

Files:
  tools/dsymutil/dsymutil.cpp


Index: tools/dsymutil/dsymutil.cpp
===================================================================
--- tools/dsymutil/dsymutil.cpp
+++ tools/dsymutil/dsymutil.cpp
@@ -12,18 +12,19 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "dsymutil.h"
 #include "DebugMap.h"
 #include "MachOUtils.h"
-#include "dsymutil.h"
 #include "llvm/Object/MachO.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Options.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/Signals.h"
-#include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/raw_ostream.h"
 #include <cstdint>
 #include <string>
 
@@ -61,6 +62,13 @@
                          init(false), cat(DsymCategory));
 static alias FlatOutA("f", desc("Alias for --flat"), aliasopt(FlatOut));
 
+static opt<unsigned> Threads(
+    "threads",
+    desc("Specifies the maximum number (n) of simultaneous threads to use\n"
+         "when linking multiple architectures."),
+    init(0), cat(DsymCategory));
+static alias ThreadsA("t", desc("Alias for --threads"), aliasopt(Threads));
+
 static opt<bool> Verbose("verbose", desc("Verbosity level"), init(false),
                          cat(DsymCategory));
 
@@ -316,6 +324,15 @@
       exitDsymutil(1);
     }
 
+    int NumThreads = Threads;
+    if (!NumThreads)
+      NumThreads = std::min(llvm::thread::hardware_concurrency(),
+                            (unsigned int)DebugMapPtrsOrErr->size());
+    if (DumpDebugMap || Verbose)
+      NumThreads = 1;
+
+    llvm::ThreadPool Threads(NumThreads);
+
     // If there is more than one link to execute, we need to generate
     // temporary files.
     bool NeedsTempFiles = !DumpDebugMap && (*DebugMapPtrsOrErr).size() != 1;
@@ -333,14 +350,27 @@
                      << ")\n";
 
       std::string OutputFile = getOutputFileName(InputFile, NeedsTempFiles);
-      if (OutputFile.empty() || !linkDwarf(OutputFile, *Map, Options))
-        exitDsymutil(1);
+
+      auto LinkLambda = [OutputFile, Options, &Map]() {
+        if (OutputFile.empty() || !linkDwarf(OutputFile, *Map, Options))
+          exitDsymutil(1);
+      };
+
+      // FIXME: The DwarfLinker can have some very deep recursion that can max
+      // out the (significantly smaller) stack when using threads. We don't
+      // want this limitation when we only have a single thread.
+      if (NumThreads == 1)
+        LinkLambda();
+      else
+        Threads.async(LinkLambda);
 
       if (NeedsTempFiles)
         TempFiles.emplace_back(Map->getTriple().getArchName().str(),
                                OutputFile);
     }
 
+    Threads.wait();
+
     if (NeedsTempFiles &&
         !MachOUtils::generateUniversalBinary(
             TempFiles, getOutputFileName(InputFile), Options, SDKPath))


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