[clang][IFS] Driver pipeline: generate interface stubs after standard pipeline.

Up until now, clang interface stubs has replaced the standard
PP -> C -> BE -> ASM -> LNK pipeline. With this change, it will happen in
conjunction with it. So what when you build your code you will get an
a.out or lib.so as well as an interface stub file.

Example:

clang -shared -o libfoo.so -emit-interface-stubs ...

will generate both a libfoo.so and a libfoo.ifso. The .so file will
contain the code from the standard compilation pipeline and the .ifso
file will contain the ELF stub library.

Differential Revision: https://reviews.llvm.org/D70274

clang/lib/Driver/Driver.cpp

@@ -292,10 +292,6 @@ phases::ID Driver::getFinalPhase(const DerivedArgList &DAL,
              (PhaseArg = DAL.getLastArg(options::OPT_emit_ast))) {
     FinalPhase = phases::Compile;
 
-  // clang interface stubs
-  } else if ((PhaseArg = DAL.getLastArg(options::OPT_emit_interface_stubs))) {
-    FinalPhase = phases::IfsMerge;
-
   // -S only runs up to the backend.
   } else if ((PhaseArg = DAL.getLastArg(options::OPT_S))) {
     FinalPhase = phases::Backend;
@@ -3502,6 +3498,68 @@ void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
     Actions.push_back(
         C.MakeAction<IfsMergeJobAction>(MergerInputs, types::TY_Image));
 
+  if (Arg *A = Args.getLastArg(options::OPT_emit_interface_stubs)) {
+    llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> PhaseList;
+    if (Args.hasArg(options::OPT_c)) {
+      llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> CompilePhaseList;
+      types::getCompilationPhases(types::TY_IFS_CPP, CompilePhaseList);
+      llvm::copy_if(PhaseList, std::back_inserter(CompilePhaseList),
+                    [&](phases::ID Phase) { return Phase <= phases::Compile; });
+    } else {
+      types::getCompilationPhases(types::TY_IFS_CPP, PhaseList);
+    }
+
+    ActionList MergerInputs;
+
+    for (auto &I : Inputs) {
+      types::ID InputType = I.first;
+      const Arg *InputArg = I.second;
+
+      // Currently clang and the llvm assembler do not support generating symbol
+      // stubs from assembly, so we skip the input on asm files. For ifs files
+      // we rely on the normal pipeline setup in the pipeline setup code above.
+      if (InputType == types::TY_IFS || InputType == types::TY_PP_Asm ||
+          InputType == types::TY_Asm)
+        continue;
+
+      Action *Current = C.MakeAction<InputAction>(*InputArg, InputType);
+
+      for (auto Phase : PhaseList) {
+        switch (Phase) {
+        default:
+          llvm_unreachable(
+              "IFS Pipeline can only consist of Compile followed by IfsMerge.");
+        case phases::Compile: {
+          // Only IfsMerge (llvm-ifs) can handle .o files by looking for ifs
+          // files where the .o file is located. The compile action can not
+          // handle this.
+          if (InputType == types::TY_Object)
+            break;
+
+          Current = C.MakeAction<CompileJobAction>(Current, types::TY_IFS_CPP);
+          break;
+        }
+        case phases::IfsMerge: {
+          assert(Phase == PhaseList.back() &&
+                 "merging must be final compilation step.");
+          MergerInputs.push_back(Current);
+          Current = nullptr;
+          break;
+        }
+        }
+      }
+
+      // If we ended with something, add to the output list.
+      if (Current)
+        Actions.push_back(Current);
+    }
+
+    // Add an interface stubs merge action if necessary.
+    if (!MergerInputs.empty())
+      Actions.push_back(
+          C.MakeAction<IfsMergeJobAction>(MergerInputs, types::TY_Image));
+  }
+
   // If --print-supported-cpus, -mcpu=? or -mtune=? is specified, build a custom
   // Compile phase that prints out supported cpu models and quits.
   if (Arg *A = Args.getLastArg(options::OPT_print_supported_cpus)) {
@@ -3603,8 +3661,6 @@ Action *Driver::ConstructPhaseAction(
       return C.MakeAction<CompileJobAction>(Input, types::TY_ModuleFile);
     if (Args.hasArg(options::OPT_verify_pch))
       return C.MakeAction<VerifyPCHJobAction>(Input, types::TY_Nothing);
-    if (Args.hasArg(options::OPT_emit_interface_stubs))
-      return C.MakeAction<CompileJobAction>(Input, types::TY_IFS_CPP);
     return C.MakeAction<CompileJobAction>(Input, types::TY_LLVM_BC);
   }
   case phases::Backend: {
@@ -3633,11 +3689,16 @@ void Driver::BuildJobs(Compilation &C) const {
   Arg *FinalOutput = C.getArgs().getLastArg(options::OPT_o);
 
   // It is an error to provide a -o option if we are making multiple output
-  // files.
+  // files. There is one exception, IfsMergeJob: when generating interface stubs
+  // enabled we want to be able to generate the stub file at the same time that
+  // we generate the real library/a.out. So when a .o, .so, etc are the output,
+  // with clang interface stubs there will also be a .ifs and .ifso at the same
+  // location.
   if (FinalOutput) {
     unsigned NumOutputs = 0;
     for (const Action *A : C.getActions())
-      if (A->getType() != types::TY_Nothing)
+      if (A->getType() != types::TY_Nothing &&
+          A->getKind() != Action::IfsMergeJobClass)
         ++NumOutputs;
 
     if (NumOutputs > 1) {

clang/lib/Driver/ToolChains/InterfaceStubs.cpp

@@ -9,6 +9,7 @@
 #include "InterfaceStubs.h"
 #include "CommonArgs.h"
 #include "clang/Driver/Compilation.h"
+#include "llvm/Support/Path.h"
 
 namespace clang {
 namespace driver {
@@ -21,13 +22,36 @@ void Merger::ConstructJob(Compilation &C, const JobAction &JA,
   std::string Merger = getToolChain().GetProgramPath(getShortName());
   llvm::opt::ArgStringList CmdArgs;
   CmdArgs.push_back("-action");
-  CmdArgs.push_back(Args.getLastArg(options::OPT_emit_merged_ifs)
-                        ? "write-ifs"
-                        : "write-bin");
+  const bool WriteBin = !Args.getLastArg(options::OPT_emit_merged_ifs);
+  CmdArgs.push_back(WriteBin ? "write-bin" : "write-ifs");
   CmdArgs.push_back("-o");
-  CmdArgs.push_back(Output.getFilename());
-  for (const auto &Input : Inputs)
-    CmdArgs.push_back(Input.getFilename());
+
+  // Normally we want to write to a side-car file ending in ".ifso" so for
+  // example if `clang -emit-interface-stubs -shared -o libhello.so` were
+  // invoked then we would like to get libhello.so and libhello.ifso. If the
+  // stdout stream is given as the output file (ie `-o -`), that is the one
+  // exception where we will just append to the same filestream as the normal
+  // output.
+  SmallString<128> OutputFilename(Output.getFilename());
+  if (OutputFilename != "-") {
+    if (Args.hasArg(options::OPT_shared))
+      llvm::sys::path::replace_extension(OutputFilename,
+                                         (WriteBin ? "ifso" : "ifs"));
+    else
+      OutputFilename += ".ifso";
+  }
+
+  CmdArgs.push_back(Args.MakeArgString(OutputFilename.c_str()));
+
+  // Here we append the input files. If the input files are object files, then
+  // we look for .ifs files present in the same location as the object files.
+  for (const auto &Input : Inputs) {
+    SmallString<128> InputFilename(Input.getFilename());
+    if (Input.getType() == types::TY_Object)
+      llvm::sys::path::replace_extension(InputFilename, ".ifs");
+    CmdArgs.push_back(Args.MakeArgString(InputFilename.c_str()));
+  }
+
   C.addCommand(std::make_unique<Command>(JA, *this, Args.MakeArgString(Merger),
                                          CmdArgs, Inputs));
 }

clang/lib/Driver/Types.cpp

@@ -330,22 +330,6 @@ void types::getCompilationPhases(const clang::driver::Driver &Driver,
     llvm::copy_if(PhaseList, std::back_inserter(P),
                   [](phases::ID Phase) { return Phase <= phases::Precompile; });
 
-  // Treat Interface Stubs like its own compilation mode.
-  else if (DAL.getLastArg(options::OPT_emit_interface_stubs)) {
-    llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> IfsModePhaseList;
-    llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> &PL = PhaseList;
-    phases::ID LastPhase = phases::IfsMerge;
-    if (Id != types::TY_IFS) {
-      if (DAL.hasArg(options::OPT_c))
-        LastPhase = phases::Compile;
-      PL = IfsModePhaseList;
-      types::getCompilationPhases(types::TY_IFS_CPP, PL);
-    }
-    llvm::copy_if(PL, std::back_inserter(P), [&](phases::ID Phase) {
-      return Phase <= LastPhase;
-    });
-  }
-
   // -{fsyntax-only,-analyze,emit-ast} only run up to the compiler.
   else if (DAL.getLastArg(options::OPT_fsyntax_only) ||
            DAL.getLastArg(options::OPT_print_supported_cpus) ||

clang/test/InterfaceStubs/driver-test.c

@@ -1,11 +1,13 @@
 // REQUIRES: x86-registered-target
 
-// RUN: %clang -target x86_64-unknown-linux-gnu -x c -o %t1.so -emit-interface-stubs %s %S/object.c %S/weak.cpp && \
-// RUN: llvm-nm %t1.so 2>&1 | FileCheck --check-prefix=CHECK-IFS %s
+// RUN: %clang -target x86_64-unknown-linux-gnu -x c -o %t1 -emit-interface-stubs %s %S/object.c %S/weak.cpp
+// RUN: llvm-nm %t1 2>&1 | FileCheck %s
+// RUN: llvm-nm %t1.ifso 2>&1 | FileCheck %s
 
-// CHECK-IFS-DAG: data
-// CHECK-IFS-DAG: foo
-// CHECK-IFS-DAG: strongFunc
-// CHECK-IFS-DAG: weakFunc
+// CHECK-DAG: data
+// CHECK-DAG: foo
+// CHECK-DAG: strongFunc
+// CHECK-DAG: weakFunc
 
 int foo(int bar) { return 42 + 1844; }
+int main() { return foo(23); }

clang/test/InterfaceStubs/driver-test2.c

@@ -0,0 +1,14 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clang -target x86_64-unknown-linux-gnu -c -emit-interface-stubs \
+// RUN:   %s %S/object.c %S/weak.cpp
+// RUN: %clang -emit-interface-stubs -emit-merged-ifs \
+// RUN:   driver-test2.o object.o weak.o -S -o - | FileCheck %s
+
+// CHECK-DAG: data
+// CHECK-DAG: bar
+// CHECK-DAG: strongFunc
+// CHECK-DAG: weakFunc
+
+int bar(int a) { return a; }
+int main() { return 0; }

clang/test/InterfaceStubs/windows.cpp

@@ -1,6 +1,7 @@
 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 -triple x86_64-windows-msvc -o - %s -emit-interface-stubs | FileCheck -check-prefix=CHECK-CC1 %s
-// RUN: %clang -target x86_64-windows-msvc -o - %s -emit-interface-stubs -emit-merged-ifs | FileCheck -check-prefix=CHECK-IFS %s
+// RUN: %clang -target x86_64-windows-msvc -o - %s -emit-interface-stubs -emit-merged-ifs -S | FileCheck -check-prefix=CHECK-IFS %s
+// note: -S is added here to prevent clang from invoking link.exe
 
 // CHECK-CC1: Symbols:
 // CHECK-CC1-NEXT: ?helloWindowsMsvc@@YAHXZ