[DTLTO][LLD][COFF] Add support for Integrated Distributed ThinLTO

cross-project-tests/dtlto/link-archive-thin.test

@@ -0,0 +1,93 @@
+REQUIRES: lld-link
+
+## Test that a DTLTO link succeeds and outputs the expected set of files
+## correctly when thin archives are present.
+
+RUN: rm -rf %t && split-file %s %t && cd %t
+
+## Compile bitcode. -O2 is required for cross-module importing.
+RUN: %clang -O2 --target=x86_64-pc-windows-msvc -flto=thin -c \
+RUN:   foo.c bar.c dog.c cat.c start.c
+
+## Generate thin archives.
+RUN: lld-link /lib /llvmlibthin /out:foo.lib foo.o
+## Create this bitcode thin archive in a subdirectory to test the expansion of
+## the path to a bitcode file that is referenced using "..", e.g., in this case
+## "../bar.o".
+RUN: mkdir lib
+RUN: lld-link /lib /llvmlibthin /out:lib/bar.lib bar.o
+## Create this bitcode thin archive with an absolute path entry containing "..".
+RUN: lld-link /lib /llvmlibthin /out:dog.lib %t/lib/../dog.o
+RUN: lld-link /lib /llvmlibthin /out:cat.lib cat.o
+RUN: lld-link /lib /llvmlibthin /out:start.lib start.o
+
+## Link from a different directory to ensure that thin archive member paths are
+## resolved correctly relative to the archive locations.
+RUN: mkdir %t/out && cd %t/out
+RUN: lld-link /subsystem:console /machine:x64 /entry:start /out:my.exe  \
+RUN:   %t/foo.lib %t/lib/bar.lib ../start.lib %t/cat.lib \
+RUN:   /includeoptional:dog ../dog.lib \
+RUN:   /thinlto-distributor:%python \
+RUN:   /thinlto-distributor-arg:%llvm_src_root/utils/dtlto/local.py \
+RUN:   /thinlto-remote-compiler:%clang \
+RUN:   /lldsavetemps
+
+## Check that the required output files have been created.
+RUN: ls | FileCheck %s --check-prefix=OUTPUTS --implicit-check-not=cat
+
+## JSON jobs description.
+OUTPUTS-DAG: my.[[PID:[a-zA-Z0-9_]+]].dist-file.json
+
+## Individual summary index files.
+OUTPUTS-DAG: start.1.[[PID]].native.o.thinlto.bc{{$}}
+OUTPUTS-DAG:   dog.2.[[PID]].native.o.thinlto.bc{{$}}
+OUTPUTS-DAG:   foo.3.[[PID]].native.o.thinlto.bc{{$}}
+OUTPUTS-DAG:   bar.4.[[PID]].native.o.thinlto.bc{{$}}
+
+## Native output object files.
+OUTPUTS-DAG: start.1.[[PID]].native.o{{$}}
+OUTPUTS-DAG:   dog.2.[[PID]].native.o{{$}}
+OUTPUTS-DAG:   foo.3.[[PID]].native.o{{$}}
+OUTPUTS-DAG:   bar.4.[[PID]].native.o{{$}}
+
+
+## It is important that cross-module inlining occurs for this test to show that Clang can
+## successfully load the bitcode file dependencies recorded in the summary indices.
+## Explicitly check that the expected importing has occurred.
+
+RUN: llvm-dis start.1.*.native.o.thinlto.bc -o - | \
+RUN:   FileCheck %s --check-prefixes=FOO,BAR,START
+
+RUN: llvm-dis dog.2.*.native.o.thinlto.bc -o - | \
+RUN:   FileCheck %s --check-prefixes=FOO,BAR,DOG,START
+
+RUN: llvm-dis foo.3.*.native.o.thinlto.bc -o - | \
+RUN:   FileCheck %s --check-prefixes=FOO,BAR,START
+
+RUN: llvm-dis bar.4.*.native.o.thinlto.bc -o - | \
+RUN:   FileCheck %s --check-prefixes=FOO,BAR,START
+
+FOO-DAG:   foo.o
+BAR-DAG:   bar.o
+DOG-DAG:   dog.o
+START-DAG: start.o
+
+
+#--- foo.c
+extern int bar(int), start(int);
+__attribute__((retain)) int foo(int x) { return x + bar(x) + start(x); }
+
+#--- bar.c
+extern int foo(int), start(int);
+__attribute__((retain)) int bar(int x) { return x + foo(x) + start(x); }
+
+#--- dog.c
+extern int foo(int), bar(int), start(int);
+__attribute__((retain)) int dog(int x) { return x + foo(x) + bar(x) + start(x); }
+
+#--- cat.c
+__attribute__((retain)) void cat(int x) {}
+
+#--- start.c
+extern int foo(int), bar(int);
+__attribute__((retain)) int start(int x) { return x + foo(x) + bar(x); }

cross-project-tests/dtlto/link-dtlto.c

@@ -0,0 +1,41 @@
+// REQUIRES: lld-link
+
+/// Simple test that DTLTO works with a single input bitcode file and that
+/// --save-temps can be applied to the remote compilation.
+
+// RUN: rm -rf %t && mkdir %t && cd %t
+
+// RUN: %clang --target=x86_64-pc-windows-msvc -c -flto=thin %s -o dtlto.obj
+
+// RUN: lld-link /subsystem:console /entry:_start dtlto.obj \
+// RUN:   /thinlto-distributor:%python \
+// RUN:   /thinlto-distributor-arg:%llvm_src_root/utils/dtlto/local.py \
+// RUN:   /thinlto-remote-compiler:%clang \
+// RUN:   /thinlto-remote-compiler-arg:--save-temps
+
+/// Check that the required output files have been created.
+// RUN: ls | sort | FileCheck %s
+
+/// No files are expected before.
+// CHECK-NOT: {{.}}
+
+/// Linked ELF.
+// CHECK: {{^}}dtlto.exe{{$}}
+
+/// Produced by the bitcode compilation.
+// CHECK-NEXT: {{^}}dtlto.obj{{$}}
+
+/// --save-temps output for the backend compilation.
+// CHECK-NEXT: {{^}}dtlto.s{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.0.preopt.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.1.promote.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.2.internalize.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.3.import.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.4.opt.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.5.precodegen.bc{{$}}
+// CHECK-NEXT: {{^}}dtlto.s.resolution.txt{{$}}
+
+/// No files are expected after.
+// CHECK-NOT: {{.}}
+
+int _start() { return 0; }

cross-project-tests/lit.cfg.py

@@ -19,7 +19,7 @@
 config.test_format = lit.formats.ShTest(not llvm_config.use_lit_shell)
 
 # suffixes: A list of file extensions to treat as test files.
-config.suffixes = [".c", ".cl", ".cpp", ".m"]
+config.suffixes = [".c", ".cl", ".cpp", ".m", ".test"]
 
 # excludes: A list of directories to exclude from the testsuite. The 'Inputs'
 # subdirectories contain auxiliary inputs for various tests in their parent

lld/COFF/Config.h

@@ -192,6 +192,18 @@ struct Configuration {
   // Used for /lldltocachepolicy=policy
   llvm::CachePruningPolicy ltoCachePolicy;
 
+  // Used for /thinlto-distributor:<path>
+  StringRef dtltoDistributor;
+
+  // Used for /thinlto-distributor-arg:<arg>
+  llvm::SmallVector<llvm::StringRef, 0> dtltoDistributorArgs;
+
+  // Used for /thinlto-remote-compiler:<path>
+  StringRef dtltoCompiler;
+
+  // Used for /thinlto-remote-compiler-arg:<arg>
+  llvm::SmallVector<llvm::StringRef, 0> dtltoCompilerArgs;
+
   // Used for /opt:[no]ltodebugpassmanager
   bool ltoDebugPassManager = false;
 

lld/COFF/Driver.cpp

@@ -2088,6 +2088,23 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     Fatal(ctx) << "/manifestinput: requires /manifest:embed";
   }
 
+  // Handle /thinlto-distributor:<path>
+  config->dtltoDistributor = args.getLastArgValue(OPT_thinlto_distributor);
+
+  // Handle /thinlto-distributor-arg:<arg>
+  for (auto *arg : args.filtered(OPT_thinlto_distributor_arg))
+    config->dtltoDistributorArgs.push_back(arg->getValue());
+
+  // Handle /thinlto-remote-compiler:<path>
+  config->dtltoCompiler = args.getLastArgValue(OPT_thinlto_compiler);
+  if (!config->dtltoDistributor.empty() && config->dtltoCompiler.empty())
+    Err(ctx) << "A value must be specified for /thinlto-remote-compiler if "
+                "/thinlto-distributor is specified.";
+
+  // Handle /thinlto-remote-compiler-arg:<arg>
+  for (auto *arg : args.filtered(OPT_thinlto_compiler_arg))
+    config->dtltoCompilerArgs.push_back(arg->getValue());
+
   // Handle /dwodir
   config->dwoDir = args.getLastArgValue(OPT_dwodir);
 

lld/COFF/LTO.cpp

@@ -110,7 +110,16 @@ BitcodeCompiler::BitcodeCompiler(COFFLinkerContext &c) : ctx(c) {
 
   // Initialize ltoObj.
   lto::ThinBackend backend;
-  if (ctx.config.thinLTOIndexOnly) {
+  if (!ctx.config.dtltoDistributor.empty()) {
+    backend = lto::createOutOfProcessThinBackend(
+        llvm::hardware_concurrency(ctx.config.thinLTOJobs),
+        /*OnWrite=*/nullptr,
+        /*ShouldEmitIndexFiles=*/false,
+        /*ShouldEmitImportFiles=*/false, ctx.config.outputFile,
+        ctx.config.dtltoDistributor, ctx.config.dtltoDistributorArgs,
+        ctx.config.dtltoCompiler, ctx.config.dtltoCompilerArgs,
+        !ctx.config.saveTempsArgs.empty());
+  } else if (ctx.config.thinLTOIndexOnly) {
     auto OnIndexWrite = [&](StringRef S) { thinIndices.erase(S); };
     backend = lto::createWriteIndexesThinBackend(
         llvm::hardware_concurrency(ctx.config.thinLTOJobs),

lld/COFF/Options.td

@@ -270,6 +270,18 @@ def thinlto_object_suffix_replace : P<
 def thinlto_prefix_replace: P<
     "thinlto-prefix-replace",
     "'old;new' replace old prefix with new prefix in ThinLTO outputs">;
+def thinlto_distributor : P<"thinlto-distributor",
+                            "Distributor to use for ThinLTO backend "
+			    "compilations. If specified, ThinLTO backend "
+                            "compilations will be distributed">;
+def thinlto_distributor_arg : P<"thinlto-distributor-arg",
+                                "Arguments to pass to the ThinLTO distributor">;
+def thinlto_compiler : P<"thinlto-remote-compiler",
+                         "Compiler for the ThinLTO distributor to invoke for "
+                         "ThinLTO backend compilations">;
+def thinlto_compiler_arg : P<"thinlto-remote-compiler-arg",
+                             "Compiler arguments for the ThinLTO distributor "
+                             "to pass for ThinLTO backend compilations">;
 def lto_obj_path : P<
     "lto-obj-path",
     "output native object for merged LTO unit to this path">;

lld/docs/DTLTO.rst

@@ -7,8 +7,7 @@ during the traditional link step.
 
 The implementation is documented here: https://llvm.org/docs/DTLTO.html.
 
-Currently, DTLTO is only supported in ELF LLD. Support will be added to other
-LLD flavours in the future.
+Currently, DTLTO is only supported in ELF and COFF LLD.
 
 ELF LLD
 -------
@@ -40,3 +39,37 @@ The command-line interface is as follows:
 Some LLD LTO options (e.g., ``--lto-sample-profile=<file>``) are supported.
 Currently, other options are silently accepted but do not have the intended
 effect. Support for such options will be expanded in the future.
+
+COFF LLD
+--------
+
+The command-line interface is as follows:
+
+- ``/thinlto-distributor:<path>``
+  Specifies the file to execute as the distributor process. If specified,
+  ThinLTO backend compilations will be distributed.
+
+- ``/thinlto-remote-compiler:<path>``
+  Specifies the path to the compiler that the distributor process will use for
+  backend compilations. The compiler invoked must match the version of LLD.
+
+- ``/thinlto-distributor-arg:<arg>``
+  Specifies ``<arg>`` on the command line when invoking the distributor.
+  Can be specified multiple times.
+
+- ``/thinlto-remote-compiler-arg:<arg>``
+  Appends ``<arg>`` to the remote compiler's command line.
+  Can be specified multiple times.
+
+  Options that introduce extra input/output files may cause miscompilation if
+  the distribution system does not automatically handle pushing/fetching them to
+  remote nodes. In such cases, configure the distributor - possibly using
+  ``/thinlto-distributor-arg:`` - to manage these dependencies. See the
+  distributor documentation for details.
+
+Some LLD LTO options (e.g., ``/lto-sample-profile:<file>``) are supported.
+Currently, other options are silently accepted but do not have the intended
+effect. Support for such options could be expanded in the future.
+
+Currently, there is no DTLTO command line interface supplied for ``clang-cl``,
+as users are expected to invoke LLD directly.

lld/test/COFF/dtlto/files.test

@@ -0,0 +1,71 @@
+REQUIRES: x86
+
+## Test that the LLD options /lldsavetemps and -thinlto-emit-imports-files
+## function correctly with DTLTO we also check that index files 
+## (-thinlto-emit-index-files) are not emitted with DTLTO.
+
+RUN: rm -rf %t && split-file %s %t && cd %t
+
+RUN: sed 's/@t1/@t2/g' t1.ll > t2.ll
+
+## Generate ThinLTO bitcode files. Note that t3.bc will not be used by the
+## linker.
+RUN: opt -thinlto-bc t1.ll -o t1.bc
+RUN: opt -thinlto-bc t2.ll -o t2.bc
+RUN: cp t1.bc t3.bc
+
+## Generate object files for mock.py to return.
+RUN: llc t1.ll --filetype=obj -o t1.obj
+RUN: llc t2.ll --filetype=obj -o t2.obj
+
+## Create response file containing shared ThinLTO linker arguments.
+## -start-lib/-end-lib is used to test the special case where unused lazy
+## bitcode inputs result in empty index/imports files.
+## Note that mock.py does not do any compilation; instead, it simply writes
+## the contents of the object files supplied on the command line into the
+## output object files in job order.
+RUN: echo "/entry:t1 /subsystem:console \
+RUN:   t1.bc t2.bc -start-lib t3.bc -end-lib /out:my.exe \
+RUN:   /thinlto-distributor:\"%python\" \
+RUN:   /thinlto-distributor-arg:\"%llvm_src_root/utils/dtlto/mock.py\" \
+RUN:   /thinlto-distributor-arg:t1.obj \
+RUN:   /thinlto-distributor-arg:t2.obj \
+RUN:   /thinlto-remote-compiler:fake.exe" > l.rsp
+
+## Check that without extra flags, no index/imports files are produced and
+## backend temp files are removed.
+RUN: lld-link @l.rsp
+RUN: ls | FileCheck %s \
+RUN:   --check-prefixes=NOBACKEND,NOOTHERS
+
+## Check that with /lldsavetemps and -thinlto-emit-imports-files backend 
+## tempoary files are retained and no index/imports files are produced.
+RUN: rm -f *.imports *.thinlto.bc
+RUN: lld-link @l.rsp  /lldsavetemps -thinlto-emit-imports-files
+RUN: ls | sort | FileCheck %s \
+RUN:   --check-prefixes=BACKEND,NOOTHERS
+
+## JSON jobs description, retained with --save-temps.
+## Note that DTLTO temporary files include a PID component.
+NOBACKEND-NOT: {{^}}my.[[#]].dist-file.json{{$}}
+BACKEND:       {{^}}my.[[#]].dist-file.json{{$}}
+
+## Index/imports files for t1.bc.
+NOOTHERS-NOT: {{^}}t1.bc.imports{{$}}
+NOOTHERS-NOT: {{^}}t1.bc.thinlto.bc{{$}}
+
+## Index/imports files for t2.bc.
+NOOTHERS-NOT: {{^}}t2.bc.imports{{$}}
+NOOTHERS-NOT: {{^}}t2.bc.thinlto.bc{{$}}
+
+## Empty index/imports files for unused t3.bc.
+NOOTHERS-NOT: {{^}}t3.bc.imports{{$}}
+NOOTHERS-NOT: {{^}}t3.bc.thinlto.bc{{$}}
+
+#--- t1.ll
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @t1() {
+  ret void
+}