[ThinLTO] Pass -save-temps to LTO backend for distributed ThinLTO builds

Summary:
The clang driver option -save-temps was not passed to the LTO config,
so when invoking the ThinLTO backends via clang during distributed
builds there was no way to get LTO to save temp files.

Getting this to work with ThinLTO distributed builds also required
changing the driver to avoid a separate compile step to emit unoptimized
bitcode when the input was already bitcode under -save-temps. Not only is
this unnecessary in general, it is problematic for ThinLTO backends since
the temporary bitcode file to the backend would not match the module path
in the combined index, leading to incorrect ThinLTO backend index-based
optimizations.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, cfe-commits

Differential Revision: https://reviews.llvm.org/D45217

llvm-svn: 330194

8 files changed, 61 insertions, 7 deletions

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index fa4777a1447..5a3a7442acb 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2275,7 +2275,7 @@ def fno_rtlib_add_rpath: Flag<["-"], "fno-rtlib-add-rpath">, Flags<[NoArgumentUn
   HelpText<"Do not add -rpath with architecture-specific resource directory to the linker flags">;
 def r : Flag<["-"], "r">, Flags<[LinkerInput,NoArgumentUnused]>,
         Group<Link_Group>;
-def save_temps_EQ : Joined<["-", "--"], "save-temps=">, Flags<[DriverOption]>,
+def save_temps_EQ : Joined<["-", "--"], "save-temps=">, Flags<[CC1Option, DriverOption]>,
   HelpText<"Save intermediate compilation results.">;
 def save_temps : Flag<["-", "--"], "save-temps">, Flags<[DriverOption]>,
   Alias<save_temps_EQ>, AliasArgs<["cwd"]>,
diff --git a/clang/include/clang/Frontend/CodeGenOptions.h b/clang/include/clang/Frontend/CodeGenOptions.h
index 6ab64f65623..3307c504080 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.h
+++ b/clang/include/clang/Frontend/CodeGenOptions.h
@@ -203,6 +203,9 @@ public:
   /// the summary and module symbol table (and not, e.g. any debug metadata).
   std::string ThinLinkBitcodeFile;
 
+  /// Prefix to use for -save-temps output.
+  std::string SaveTempsFilePrefix;
+
   /// Name of file passed with -fcuda-include-gpubinary option to forward to
   /// CUDA runtime back-end for incorporating them into host-side object file.
   std::string CudaGpuBinaryFileName;
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 67af3aeb948..cf0251b46e4 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1117,6 +1117,15 @@ static void runThinLTOBackend(ModuleSummaryIndex *CombinedIndex, Module *M,
     return llvm::make_unique<lto::NativeObjectStream>(std::move(OS));
   };
   lto::Config Conf;
+  if (CGOpts.SaveTempsFilePrefix != "") {
+    if (Error E = Conf.addSaveTemps(CGOpts.SaveTempsFilePrefix + ".",
+                                    /* UseInputModulePath */ false)) {
+      handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
+        errs() << "Error setting up ThinLTO save-temps: " << EIB.message()
+               << '\n';
+      });
+    }
+  }
   Conf.CPU = TOpts.CPU;
   Conf.CodeModel = getCodeModel(CGOpts);
   Conf.MAttrs = TOpts.Features;
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index e2c241143fa..f83b3197269 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -3379,19 +3379,34 @@ class ToolSelector final {
   const Tool *combineBackendCompile(ArrayRef<JobActionInfo> ActionInfo,
                                     const ActionList *&Inputs,
                                     ActionList &CollapsedOffloadAction) {
-    if (ActionInfo.size() < 2 || !canCollapsePreprocessorAction())
+    if (ActionInfo.size() < 2)
       return nullptr;
     auto *BJ = dyn_cast<BackendJobAction>(ActionInfo[0].JA);
     auto *CJ = dyn_cast<CompileJobAction>(ActionInfo[1].JA);
     if (!BJ || !CJ)
       return nullptr;
 
+    // Check if the initial input (to the compile job or its predessor if one
+    // exists) is LLVM bitcode. In that case, no preprocessor step is required
+    // and we can still collapse the compile and backend jobs when we have
+    // -save-temps. I.e. there is no need for a separate compile job just to
+    // emit unoptimized bitcode.
+    bool InputIsBitcode = true;
+    for (size_t i = 1; i < ActionInfo.size(); i++)
+      if (ActionInfo[i].JA->getType() != types::TY_LLVM_BC &&
+          ActionInfo[i].JA->getType() != types::TY_LTO_BC) {
+        InputIsBitcode = false;
+        break;
+      }
+    if (!InputIsBitcode && !canCollapsePreprocessorAction())
+      return nullptr;
+
     // Get compiler tool.
     const Tool *T = TC.SelectTool(*CJ);
     if (!T)
       return nullptr;
 
-    if (T->canEmitIR() && (SaveTemps || EmbedBitcode))
+    if (T->canEmitIR() && ((SaveTemps && !InputIsBitcode) || EmbedBitcode))
       return nullptr;
 
     Inputs = &CJ->getInputs();
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index f6c0061387d..49a0c4cdc1a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3267,6 +3267,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     Args.AddLastArg(CmdArgs, options::OPT_fthinlto_index_EQ);
   }
 
+  if (const Arg *A = Args.getLastArg(options::OPT_save_temps_EQ))
+    Args.AddLastArg(CmdArgs, options::OPT_save_temps_EQ);
+
   // Embed-bitcode option.
   if (C.getDriver().embedBitcodeInObject() && !C.getDriver().isUsingLTO() &&
       (isa<BackendJobAction>(JA) || isa<AssembleJobAction>(JA))) {
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 147657f62fc..3ff5fcd14af 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -507,7 +507,8 @@ static void setPGOUseInstrumentor(CodeGenOptions &Opts,
 
 static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                              DiagnosticsEngine &Diags,
-                             const TargetOptions &TargetOpts) {
+                             const TargetOptions &TargetOpts,
+                             const FrontendOptions &FrontendOpts) {
   bool Success = true;
   llvm::Triple Triple = llvm::Triple(TargetOpts.Triple);
 
@@ -758,6 +759,12 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
           << A->getAsString(Args) << "-x ir";
     Opts.ThinLTOIndexFile = Args.getLastArgValue(OPT_fthinlto_index_EQ);
   }
+  if (Arg *A = Args.getLastArg(OPT_save_temps_EQ))
+    Opts.SaveTempsFilePrefix =
+        llvm::StringSwitch<std::string>(A->getValue())
+            .Case("obj", FrontendOpts.OutputFile)
+            .Default(llvm::sys::path::filename(FrontendOpts.OutputFile).str());
+
   Opts.ThinLinkBitcodeFile = Args.getLastArgValue(OPT_fthin_link_bitcode_EQ);
 
   Opts.MSVolatile = Args.hasArg(OPT_fms_volatile);
@@ -2927,7 +2934,7 @@ bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
                                       LangOpts.IsHeaderFile);
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   Success &= ParseCodeGenArgs(Res.getCodeGenOpts(), Args, DashX, Diags,
-                              Res.getTargetOpts());
+                              Res.getTargetOpts(), Res.getFrontendOpts());
   ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args,
                         Res.getFileSystemOpts().WorkingDir);
   if (DashX.getFormat() == InputKind::Precompiled ||
diff --git a/clang/test/CodeGen/thinlto_backend.ll b/clang/test/CodeGen/thinlto_backend.ll
index 40530ec5364..5b1964ac7d5 100644
--- a/clang/test/CodeGen/thinlto_backend.ll
+++ b/clang/test/CodeGen/thinlto_backend.ll
@@ -26,8 +26,16 @@
 ; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t4.o -x ir %t5.o -c -fthinlto-index=%t.thinlto.bc
 ; RUN: llvm-nm %t4.o | count 0
 
-; Ensure f2 was imported
-; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t3.o -x ir %t1.o -c -fthinlto-index=%t.thinlto.bc
+; Ensure f2 was imported. Check for all 3 flavors of -save-temps[=cwd|obj].
+; RUN: %clang -target x86_64-unknown-linux-gnu -O2 -o %t3.o -x ir %t1.o -c -fthinlto-index=%t.thinlto.bc -save-temps=obj
+; RUN: llvm-dis %t1.s.0.3.import.bc -o - | FileCheck --check-prefix=CHECK-IMPORT %s
+; RUN: mkdir -p %T/dir1
+; RUN: (cd %T/dir1 && %clang -target x86_64-unknown-linux-gnu -O2 -o %t3.o -x ir %t1.o -c -fthinlto-index=%t.thinlto.bc -save-temps=cwd)
+; RUN: llvm-dis %T/dir1/*1.s.0.3.import.bc -o - | FileCheck --check-prefix=CHECK-IMPORT %s
+; RUN: mkdir -p %T/dir2
+; RUN: (cd %T/dir2 && %clang -target x86_64-unknown-linux-gnu -O2 -o %t3.o -x ir %t1.o -c -fthinlto-index=%t.thinlto.bc -save-temps)
+; RUN: llvm-dis %T/dir2/*1.s.0.3.import.bc -o - | FileCheck --check-prefix=CHECK-IMPORT %s
+; CHECK-IMPORT: define available_externally void @f2()
 ; RUN: llvm-nm %t3.o | FileCheck --check-prefix=CHECK-OBJ %s
 ; CHECK-OBJ: T f1
 ; CHECK-OBJ-NOT: U f2
diff --git a/clang/test/Driver/thinlto_backend.c b/clang/test/Driver/thinlto_backend.c
index 6def5821b6a..b2b45f57088 100644
--- a/clang/test/Driver/thinlto_backend.c
+++ b/clang/test/Driver/thinlto_backend.c
@@ -5,6 +5,15 @@
 // RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -### 2>&1 | FileCheck %s -check-prefix=CHECK-THINLTOBE-ACTION
 // CHECK-THINLTOBE-ACTION: -fthinlto-index=
 
+// -save-temps should be passed to cc1
+// RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-CWD
+// RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps=cwd -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-CWD
+// RUN: %clang -O2 -o %t1.o -x ir %t.o -c -fthinlto-index=%t.thinlto.bc -save-temps=obj -### 2>&1 | FileCheck %s -check-prefix=CHECK-SAVE-TEMPS -check-prefix=CHECK-SAVE-TEMPS-OBJ
+// CHECK-SAVE-TEMPS-NOT: -emit-llvm-bc
+// CHECK-SAVE-TEMPS-CWD: -save-temps=cwd
+// CHECK-SAVE-TEMPS-OBJ: -save-temps=obj
+// CHECK-SAVE-TEMPS-NOT: -emit-llvm-bc
+
 // Ensure clang driver gives the expected error for incorrect input type
 // RUN: not %clang -O2 -o %t1.o %s -c -fthinlto-index=%t.thinlto.bc 2>&1 | FileCheck %s -check-prefix=CHECK-WARNING
 // CHECK-WARNING: error: invalid argument '-fthinlto-index={{.*}}' only allowed with '-x ir'