[Driver] Enable --rtlib option for MSVC target

[roman.shirokiy]

Summary

This enables "--rtlib compiler-rt" option under MSVC environment.

Related compiler-rt patch:
http://reviews.llvm.org/D17452

[roman.shirokiy]

For now every native Windows installation of Clang contains small compiler-rt builtins lib (rL261432: [CMake] Add partial support for MSVC in compiler-rt builtins), but there is no specific interface to make use of this lib on Windows. This patch is ought to provide command line option (existing one) for linking compiler-rt builtins lib on user demand.

[rengolin]

Hi,

The error is very sensible, but I'm not sure why you're adding compiler-rt in the second change. Why is that necessary, and where are the tests for it.

Thanks!
--renato

[roman.shirokiy]

Hello!

Thanks for the feedback!

MSVC got its own runtime lib, so the function "AddRunTimeLibs" is not used anywhere in "visualstudio::Linker::Constructjob" i.e. "--rtlib" option is currently unused in MSVC environment (there is always a warning: argument unused during compilation').

if (!Args.hasArg(options::OPT_nostdlib)) {
  AddRunTimeLibs(TC, TC.getDriver(), CmdArgs, Args);
}

This change is necessary to actually handle "--rtlib" on MSVC, but I totally agree that test for "-nostdlib --rtlib=compiler-rt" case is missed.

[roman.shirokiy]

Updated diff with the test for "nostdlib" + "rtlib" case.

[rnk]

lgtm

lib/Driver/Tools.cpp

8948 ↗

(On Diff #50260)

Can you make sure you didn't change the indentation of this line? It should be two spaces left of the 'break' above.

cfe/trunk/lib/Driver/Tools.cpp

default:
       llvm_unreachable("unsupported OS");
     case llvm::Triple::Win32:
     case llvm::Triple::Linux:
       addClangRT(TC, Args, CmdArgs);
       break;
     }
     break;
   case ToolChain::RLT_Libgcc:
+    // Make sure libgcc is not used under MSVC environment by default
+    if (TC.getTriple().isKnownWindowsMSVCEnvironment()) {
+      // Issue error diagnostic if libgcc is explicitly specified
+      // through command line as --rtlib option argument.
+      if (Args.hasArg(options::OPT_rtlib_EQ)) {
+        TC.getDriver().Diag(diag::err_drv_unsupported_rtlib_for_platform)
+            << Args.getLastArg(options::OPT_rtlib_EQ)->getValue() << "MSVC";
+      }
+    } else
       AddLibgcc(TC.getTriple(), D, CmdArgs, Args);
     break;
   }
 }
 
 static const char *getLDMOption(const llvm::Triple &T, const ArgList &Args) {
   switch (T.getArch()) {
   case llvm::Triple::x86:
     return "elf_i386";
if (Args.hasFlag(options::OPT_fopenmp, options::OPT_fopenmp_EQ,
     case OMPRT_GOMP:
       break;
     case OMPRT_Unknown:
       // Already diagnosed.
       break;
     }
   }
 
+  // Add compiler-rt lib in case if it was explicitly
+  // specified as an argument for --rtlib option.
+  if (!Args.hasArg(options::OPT_nostdlib)) {
+    AddRunTimeLibs(TC, TC.getDriver(), CmdArgs, Args);
+  }
+
   // Add filenames, libraries, and other linker inputs.
   for (const auto &Input : Inputs) {
     if (Input.isFilename()) {
       CmdArgs.push_back(Input.getFilename());
       continue;
     }
 
     const Arg &A = Input.getInputArg();

cfe/trunk/test/Driver/msvc-compiler-rt.c

+// RUN: %clang -target x86_64-pc-windows-msvc --rtlib=compiler-rt -### %s 2>&1 | FileCheck %s -check-prefix MSVC-COMPILER-RT
+// RUN: not %clang %s -target x86_64-pc-windows-msvc --rtlib=libgcc 2>&1 | FileCheck %s -check-prefix CHECK-ERROR
+
+// MSVC-COMPILER-RT: "{{.*}}clang_rt.builtins{{.*}}"
+// CHECK-ERROR: unsupported runtime library 'libgcc' for platform 'MSVC'

cfe/trunk/test/Driver/nostdlib.c

 // RUN:     -resource-dir=%S/Inputs/resource_dir -lclang_rt.builtins-i686 \
 // RUN:   | FileCheck --check-prefix=CHECK-LINUX-NOSTDLIB %s
 //
 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target i686-pc-linux-gnu --rtlib=compiler-rt -nostdlib \
 // RUN:     -resource-dir=%S/Inputs/resource_dir -lclang_rt.builtins-i686 \
 // RUN:   | FileCheck --check-prefix=CHECK-LINUX-NOSTDLIB %s
 //
+// RUN: %clang -target x86_64-pc-windows-msvc -nostdlib --rtlib=compiler-rt -### %s 2>&1 | FileCheck %s -check-prefix CHECK-MSVC-NOSTDLIB
+// RUN: %clang -target x86_64-pc-windows-msvc --rtlib=compiler-rt -nostdlib -### %s 2>&1 | FileCheck %s -check-prefix CHECK-MSVC-NOSTDLIB
+//
 // CHECK-LINUX-NOSTDLIB: warning: argument unused during compilation: '--rtlib=compiler-rt'
 // CHECK-LINUX-NOSTDLIB: "{{(.*[^.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
 // CHECK-LINUX-NOSTDLIB-NOT: "{{.*}}/Inputs/resource_dir{{/|\\\\}}lib{{/|\\\\}}linux{{/|\\\\}}libclang_rt.builtins-i686.a"
+// CHECK-MSVC-NOSTDLIB: warning: argument unused during compilation: '--rtlib=compiler-rt'