[DTLTO] Refactor the DTLTO code.

DTLTO implementation code has been moved from `llvm/lib/LTO/` to `llvm/lib/DTLTO/`.
This refactor does not change any externally visible behavior,
so existing DTLTO tests and documentation remain valid.
The move was done to reduce code duplication, improve maintainability,
and make it easier to adopt future performance improvements.

Author: kbelochapka

cross-project-tests/dtlto/dtlto-cache.test

@@ -31,8 +31,8 @@ RUN:   -Wl,--thinlto-remote-compiler=%clang \
 RUN:   -Wl,--thinlto-cache-dir=cache.dir \
 RUN:   -Wl,--save-temps
 
-# Check that there are no backend compilation jobs occurred.
-RUN: grep -wo args populate2.*.dist-file.json | wc -l | grep -qx "\s*1"
+# At this point we expect full cache hits. Distributor will not be invoked and a Json file will not be created.
+RUN: not ls cache.dir/*.dist-file.json
 RUN: ls cache.dir | count 3
 
 RUN: %clang -O0 --target=x86_64-linux-gnu -flto=thin -c foo.c -o foo.O0.o

cross-project-tests/dtlto/savetemps-lock.test

@@ -30,12 +30,12 @@ RUN:       | FileCheck %s --implicit-check-not=warning
 CHECK-DAG: Lock any files in the output directory.
 CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.[[#PID:]].dist-file.json': {{.*}}
 # Filename composition: <archive>(<member> at <offset>).<task>.<pid>.<task>.<pid>.native.o.
+CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t1.o at [[#T1_OFFSET:]]).1.[[#%X,HEXPID:]].o': {{.*}}
 CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t1.o at [[#T1_OFFSET:]]).1.[[#%X,HEXPID:]].1.[[#PID]].native.o': {{.*}}
 CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t1.o at [[#T1_OFFSET]]).1.[[#%X,HEXPID]].1.[[#PID]].native.o.thinlto.bc': {{.*}}
+CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t2.o at [[#T2_OFFSET:]]).2.[[#%X,HEXPID]].o': {{.*}}
 CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t2.o at [[#T2_OFFSET:]]).2.[[#%X,HEXPID]].2.[[#PID]].native.o': {{.*}}
 CHECK-DAG: warning: could not remove the file 'locked{{/|\\}}t.a(t2.o at [[#T2_OFFSET]]).2.[[#%X,HEXPID]].2.[[#PID]].native.o.thinlto.bc': {{.*}}
-CHECK-DAG: warning: could not remove temporary DTLTO input file 'locked{{/|\\}}t.a(t1.o at [[#T1_OFFSET]]).1.[[#%X,HEXPID]].o': {{.*}}
-CHECK-DAG: warning: could not remove temporary DTLTO input file 'locked{{/|\\}}t.a(t2.o at [[#T2_OFFSET]]).2.[[#%X,HEXPID]].o': {{.*}}
 
 #--- t1.c
 __attribute__((retain)) int t1(int x) { return x; }

lld/COFF/LTO.cpp

@@ -126,17 +126,7 @@ BitcodeCompiler::BitcodeCompiler(COFFLinkerContext &c) : ctx(c) {
 
   // Initialize ltoObj.
   lto::ThinBackend backend;
-  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.dtltoCompilerPrependArgs,
-        ctx.config.dtltoCompilerArgs, !ctx.config.saveTempsArgs.empty(),
-        createAddBufferFn(files, file_names));
-  } else if (ctx.config.thinLTOIndexOnly) {
+  if (ctx.config.thinLTOIndexOnly || !ctx.config.dtltoDistributor.empty()) {
     auto OnIndexWrite = [&](StringRef S) { thinIndices.erase(S); };
     backend = lto::createWriteIndexesThinBackend(
         llvm::hardware_concurrency(ctx.config.thinLTOJobs),
@@ -155,7 +145,12 @@ BitcodeCompiler::BitcodeCompiler(COFFLinkerContext &c) : ctx(c) {
   else
     ltoObj = std::make_unique<lto::DTLTO>(
         createConfig(), backend, ctx.config.ltoPartitions,
-        llvm::lto::LTO::LTOKind::LTOK_Default, ctx.config.outputFile,
+        llvm::lto::LTO::LTOKind::LTOK_Default, nullptr,
+        ctx.config.thinLTOEmitImportsFiles, ctx.config.thinLTOIndexOnly,
+        ctx.config.outputFile, ctx.config.dtltoDistributor,
+        ctx.config.dtltoDistributorArgs, ctx.config.dtltoCompiler,
+        ctx.config.dtltoCompilerPrependArgs, ctx.config.dtltoCompilerArgs,
+        createAddBufferFn(files, file_names),
         !ctx.config.saveTempsArgs.empty());
 }
 

lld/ELF/LTO.cpp

@@ -184,21 +184,13 @@ BitcodeCompiler::BitcodeCompiler(Ctx &ctx) : ctx(ctx) {
   // Initialize ltoObj.
   lto::ThinBackend backend;
   auto onIndexWrite = [&](StringRef s) { thinIndices.erase(s); };
-  if (ctx.arg.thinLTOIndexOnly) {
+  if (ctx.arg.thinLTOIndexOnly || !ctx.arg.dtltoDistributor.empty()) {
     backend = lto::createWriteIndexesThinBackend(
         llvm::hardware_concurrency(ctx.arg.thinLTOJobs),
         std::string(ctx.arg.thinLTOPrefixReplaceOld),
         std::string(ctx.arg.thinLTOPrefixReplaceNew),
         std::string(ctx.arg.thinLTOPrefixReplaceNativeObject),
         ctx.arg.thinLTOEmitImportsFiles, indexFile.get(), onIndexWrite);
-  } else if (!ctx.arg.dtltoDistributor.empty()) {
-    backend = lto::createOutOfProcessThinBackend(
-        llvm::hardware_concurrency(ctx.arg.thinLTOJobs), onIndexWrite,
-        ctx.arg.thinLTOEmitIndexFiles, ctx.arg.thinLTOEmitImportsFiles,
-        ctx.arg.outputFile, ctx.arg.dtltoDistributor,
-        ctx.arg.dtltoDistributorArgs, ctx.arg.dtltoCompiler,
-        ctx.arg.dtltoCompilerPrependArgs, ctx.arg.dtltoCompilerArgs,
-        !ctx.arg.saveTempsArgs.empty(), createAddBufferFn(files, filenames));
   } else {
     backend = lto::createInProcessThinBackend(
         llvm::heavyweight_hardware_concurrency(ctx.arg.thinLTOJobs),
@@ -210,14 +202,19 @@ BitcodeCompiler::BitcodeCompiler(Ctx &ctx) : ctx(ctx) {
       llvm::lto::LTO::LTOKind::LTOK_UnifiedThin,
       llvm::lto::LTO::LTOKind::LTOK_UnifiedRegular,
       llvm::lto::LTO::LTOKind::LTOK_Default};
+
   if (ctx.arg.dtltoDistributor.empty())
     ltoObj = std::make_unique<lto::LTO>(createConfig(ctx), backend,
                                         ctx.arg.ltoPartitions,
                                         ltoModes[ctx.arg.ltoKind]);
   else
     ltoObj = std::make_unique<lto::DTLTO>(
         createConfig(ctx), backend, ctx.arg.ltoPartitions,
-        ltoModes[ctx.arg.ltoKind], ctx.arg.outputFile,
+        ltoModes[ctx.arg.ltoKind], onIndexWrite, ctx.arg.thinLTOEmitIndexFiles,
+        ctx.arg.thinLTOEmitImportsFiles, ctx.arg.outputFile,
+        ctx.arg.dtltoDistributor, ctx.arg.dtltoDistributorArgs,
+        ctx.arg.dtltoCompiler, ctx.arg.dtltoCompilerPrependArgs,
+        ctx.arg.dtltoCompilerArgs, createAddBufferFn(files, filenames),
         !ctx.arg.saveTempsArgs.empty());
   // Initialize usedStartStop.
   if (ctx.bitcodeFiles.empty())

lld/test/ELF/dtlto/timetrace.test

@@ -32,12 +32,12 @@ RUN: %python filter_order_and_pprint.py %t.json | FileCheck %s
 ## Check that DTLTO add input file events are recorded.
 CHECK:      "name": "Add input for DTLTO"
 CHECK:      "name": "Add input for DTLTO"
-CHECK:      "name": "Remove temporary inputs for DTLTO"
+CHECK:      "name": "Remove DTLTO temporary files"
 CHECK:      "name": "Serialize bitcode input for DTLTO"
 CHECK-SAME:   "detail": "t1.a(t1.bc at [[#ARCHIVE_OFFSET:]]).1.[[PID:[A-F0-9]+]].o"
 CHECK:      "name": "Total Add input for DTLTO"
 CHECK-SAME:   "count": 2,
-CHECK:      "name": "Total Remove temporary inputs for DTLTO"
+CHECK:      "name": "Total Remove DTLTO temporary files"
 CHECK-SAME:   "count": 1,
 CHECK:      "name": "Total Serialize bitcode input for DTLTO"
 CHECK-SAME:   "count": 1,