COFF: Implement ThinLTO cache and cache pruning support.

[ruiu]

LGTM

clang/docs/ThinLTO.rst

128

Is "as of LLVM 6.0" better?

lld/COFF/Driver.cpp

880

Just like other pieces of code, I'd add

// Handle /lldltocache

It might be a bit too verbose, but I'd keep it consistent.

883

nit: you don't need {}

clang/docs/ThinLTO.rst

 
 Incremental
 -----------
 .. _incremental:
 
 ThinLTO supports fast incremental builds through the use of a cache,
 which currently must be enabled through a linker option.
 
-- gold (as of LLVM r279883):
+- gold (as of LLVM 4.0):
   ``-Wl,-plugin-opt,cache-dir=/path/to/cache``
 - ld64 (support in clang 3.9 and Xcode 8):
   ``-Wl,-cache_path_lto,/path/to/cache``
-- lld (as of LLVM r296702):
+- ELF lld (as of LLVM 5.0):
   ``-Wl,--thinlto-cache-dir=/path/to/cache``
+- COFF lld (as of LLVM trunk):
+  ``/lldltocache:/path/to/cache``
 
 Cache Pruning
 -------------
 
 To help keep the size of the cache under control, ThinLTO supports cache
-pruning. Cache pruning is supported with ld64 and ELF lld, but currently only
-ELF lld allows you to control the policy with a policy string.  The cache
-policy must be specified with a linker option.
+pruning. Cache pruning is supported with ld64 and ELF and COFF lld, but
+currently only ELF and COFF lld allow you to control the policy with a
+policy string. The cache policy must be specified with a linker option.
 
-- ELF lld (as of LLVM r298036):
+- ELF lld (as of LLVM 5.0):
   ``-Wl,--thinlto-cache-policy,POLICY``
+- COFF lld (as of LLVM trunk):
+  ``/lldltocachepolicy:POLICY``
 
 A policy string is a series of key-value pairs separated by ``:`` characters.
 Possible key-value pairs are:
 
 - ``cache_size=X%``: The maximum size for the cache directory is ``X`` percent
   of the available space on the the disk. Set to 100 to indicate no limit,
   50 to indicate that the cache size will not be left over half the available
   disk space. A value over 100 is invalid. A value of 0 disables the percentage

lld/COFF/Config.h

 //===- Config.h -------------------------------------------------*- C++ -*-===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_COFF_CONFIG_H
 #define LLD_COFF_CONFIG_H
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Object/COFF.h"
+#include "llvm/Support/CachePruning.h"
 #include <cstdint>
 #include <map>
 #include <set>
 #include <string>
 
 namespace lld {
 namespace coff {
 
struct Configuration {
   // Used for /opt:lldlto=N
   unsigned LTOOptLevel = 2;
 
   // Used for /opt:lldltojobs=N
   unsigned LTOJobs = 0;
   // Used for /opt:lldltopartitions=N
   unsigned LTOPartitions = 1;
 
+  // Used for /opt:lldltocache=path
+  StringRef LTOCache;
+  // Used for /opt:lldltocachepolicy=policy
+  llvm::CachePruningPolicy LTOCachePolicy;
+
   // Used for /merge:from=to (e.g. /merge:.rdata=.text)
   std::map<StringRef, StringRef> Merge;
 
   // Used for /section=.name,{DEKPRSW} to set section attributes.
   std::map<StringRef, uint32_t> Section;
 
   // Options for manifest files.
   ManifestKind Manifest = No;

lld/COFF/Driver.cpp

for (StringRef S : Vec) {
         error("/opt: unknown option: " + S);
     }
   }
 
   // Handle /lldsavetemps
   if (Args.hasArg(OPT_lldsavetemps))
     Config->SaveTemps = true;
 
+  if (auto *Arg = Args.getLastArg(OPT_lldltocache))
+    Config->LTOCache = Arg->getValue();
+
+  if (auto *Arg = Args.getLastArg(OPT_lldltocachepolicy)) {
+    Config->LTOCachePolicy = check(
+        parseCachePruningPolicy(Arg->getValue()),
+        Twine("/lldltocachepolicy: invalid cache policy: ") + Arg->getValue());
+  }
+
   // Handle /failifmismatch
   for (auto *Arg : Args.filtered(OPT_failifmismatch))
     checkFailIfMismatch(Arg->getValue());
 
   // Handle /merge
   for (auto *Arg : Args.filtered(OPT_merge))
     parseMerge(Arg->getValue());
 

lld/COFF/LTO.h

public:
   ~BitcodeCompiler();
 
   void add(BitcodeFile &F);
   std::vector<StringRef> compile();
 
 private:
   std::unique_ptr<llvm::lto::LTO> LTOObj;
   std::vector<SmallString<0>> Buff;
+  std::vector<std::unique_ptr<MemoryBuffer>> Files;
 };
 }
 }
 
 #endif

lld/COFF/LTO.cpp

 #include "InputFiles.h"
 #include "Symbols.h"
 #include "lld/Core/TargetOptionsCommandFlags.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/LTO/Caching.h"
 #include "llvm/LTO/Config.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
void BitcodeCompiler::add(BitcodeFile &F) {
   checkError(LTOObj->add(std::move(F.Obj), Resols));
 }
 
 // Merge all the bitcode files we have seen, codegen the result
 // and return the resulting objects.
 std::vector<StringRef> BitcodeCompiler::compile() {
   unsigned MaxTasks = LTOObj->getMaxTasks();
   Buff.resize(MaxTasks);
+  Files.resize(MaxTasks);
 
-  checkError(LTOObj->run([&](size_t Task) {
+  // The /lldltocache option specifies the path to a directory in which to cache
+  // native object files for ThinLTO incremental builds. If a path was
+  // specified, configure LTO to use it as the cache directory.
+  lto::NativeObjectCache Cache;
+  if (!Config->LTOCache.empty())
+    Cache = check(
+        lto::localCache(Config->LTOCache,
+                        [&](size_t Task, std::unique_ptr<MemoryBuffer> MB,
+                            StringRef Path) { Files[Task] = std::move(MB); }));
+
+  checkError(LTOObj->run(
+      [&](size_t Task) {
         return llvm::make_unique<lto::NativeObjectStream>(
             llvm::make_unique<raw_svector_ostream>(Buff[Task]));
-  }));
+      },
+      Cache));
+
+  if (!Config->LTOCache.empty())
+    pruneCache(Config->LTOCache, Config->LTOCachePolicy);
 
   std::vector<StringRef> Ret;
   for (unsigned I = 0; I != MaxTasks; ++I) {
     if (Buff[I].empty())
       continue;
     if (Config->SaveTemps) {
       if (I == 0)
         saveBuffer(Buff[I], Config->OutputFile + ".lto.obj");
       else
         saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.obj");
     }
     Ret.emplace_back(Buff[I].data(), Buff[I].size());
   }
+
+  for (std::unique_ptr<MemoryBuffer> &File : Files)
+    if (File)
+      Ret.push_back(File->getBuffer());
+
   return Ret;
 }

lld/COFF/Options.td

def errorlimit : P<"errorlimit",
     "Maximum number of errors to emit before stopping (0 = no limit)">;
 def export  : P<"export", "Export a function">;
 // No help text because /failifmismatch is not intended to be used by the user.
 def failifmismatch : P<"failifmismatch", "">;
 def heap    : P<"heap", "Size of the heap">;
 def implib  : P<"implib", "Import library name">;
 def libpath : P<"libpath", "Additional library search path">;
 def linkrepro : P<"linkrepro", "Dump linker invocation and input files for debugging">;
+def lldltocache : P<"lldltocache", "Path to ThinLTO cached object file directory">;
+def lldltocachepolicy : P<"lldltocachepolicy", "Pruning policy for the ThinLTO cache">;
 def lldsavetemps : F<"lldsavetemps">,
     HelpText<"Save temporary files instead of deleting them">;
 def machine : P<"machine", "Specify target platform">;
 def merge   : P<"merge", "Combine sections">;
 def mllvm   : P<"mllvm", "Options to pass to LLVM">;
 def nodefaultlib : P<"nodefaultlib", "Remove a default library">;
 def opt     : P<"opt", "Control optimizations">;
 def out     : P<"out", "Path to file to write output">;

lld/test/COFF/Inputs/lto-cache.ll

+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define i32 @main() {
+entry:
+  call void (...) @globalfunc()
+  ret i32 0
+}
+
+declare void @globalfunc(...)

lld/test/COFF/lto-cache.ll

+; REQUIRES: x86
+
+; RUN: opt -module-hash -module-summary %s -o %t.o
+; RUN: opt -module-hash -module-summary %p/Inputs/lto-cache.ll -o %t2.o
+
+; RUN: rm -Rf %t.cache && mkdir %t.cache
+; Create two files that would be removed by cache pruning due to age.
+; We should only remove files matching the pattern "llvmcache-*".
+; RUN: touch -t 197001011200 %t.cache/llvmcache-foo %t.cache/foo
+; RUN: lld-link /lldltocache:%t.cache /lldltocachepolicy:prune_after=1h /out:%t3 /entry:main %t2.o %t.o
+
+; Two cached objects, plus a timestamp file and "foo", minus the file we removed.
+; RUN: ls %t.cache | count 4
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @globalfunc() #0 {
+entry:
+  ret void
+}