Support setting default value for -rtlib at build time

This patch introduces a new cmake variable: CLANG_DEFAULT_RTLIB, thru
which we can specify a default value for -rtlib (libgcc or
compiler-rt) at build time, just like how we set the default C++
stdlib thru CLANG_DEFAULT_CXX_STDLIB.

With these two options, we can configure clang to build binaries on
Linux that have no runtime dependence on any gcc libs (libstdc++ or
libgcc_s).

Patch by Lei Zhang!

Differential Revision: https://reviews.llvm.org/D22663

llvm-svn: 276848

3 files changed, 29 insertions, 18 deletions

diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 66b76cda14a..91b364128c9 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -534,15 +534,19 @@ void ToolChain::addProfileRTLibs(const llvm::Triple &EffectiveTriple,
 
 ToolChain::RuntimeLibType ToolChain::GetRuntimeLibType(
     const ArgList &Args) const {
-  if (Arg *A = Args.getLastArg(options::OPT_rtlib_EQ)) {
-    StringRef Value = A->getValue();
-    if (Value == "compiler-rt")
-      return ToolChain::RLT_CompilerRT;
-    if (Value == "libgcc")
-      return ToolChain::RLT_Libgcc;
-    getDriver().Diag(diag::err_drv_invalid_rtlib_name)
-      << A->getAsString(Args);
-  }
+  const Arg* A = Args.getLastArg(options::OPT_rtlib_EQ);
+  StringRef LibName = A ? A->getValue() : CLANG_DEFAULT_RTLIB;
+
+  // "platform" is only used in tests to override CLANG_DEFAULT_RTLIB
+  if (LibName == "compiler-rt")
+    return ToolChain::RLT_CompilerRT;
+  else if (LibName == "libgcc")
+    return ToolChain::RLT_Libgcc;
+  else if (LibName == "platform")
+    return GetDefaultRuntimeLibType();
+
+  if (A)
+    getDriver().Diag(diag::err_drv_invalid_rtlib_name) << A->getAsString(Args);
 
   return GetDefaultRuntimeLibType();
 }
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index f05261aef30..610285e1f40 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -403,18 +403,23 @@ void DarwinClang::AddLinkSanitizerLibArgs(const ArgList &Args,
       /*AddRPath*/ true);
 }
 
+ToolChain::RuntimeLibType DarwinClang::GetRuntimeLibType(
+    const ArgList &Args) const {
+  if (Arg* A = Args.getLastArg(options::OPT_rtlib_EQ)) {
+    StringRef Value = A->getValue();
+    if (Value != "compiler-rt")
+      getDriver().Diag(diag::err_drv_unsupported_rtlib_for_platform)
+          << Value << "darwin";
+  }
+
+  return ToolChain::RLT_CompilerRT;
+}
+
 void DarwinClang::AddLinkRuntimeLibArgs(const llvm::Triple &EffectiveTriple,
                                         const ArgList &Args,
                                         ArgStringList &CmdArgs) const {
-  // Darwin only supports the compiler-rt based runtime libraries.
-  switch (GetRuntimeLibType(Args)) {
-  case ToolChain::RLT_CompilerRT:
-    break;
-  default:
-    getDriver().Diag(diag::err_drv_unsupported_rtlib_for_platform)
-        << Args.getLastArg(options::OPT_rtlib_EQ)->getValue() << "darwin";
-    return;
-  }
+  // Call once to ensure diagnostic is printed if wrong value was specified
+  GetRuntimeLibType(Args);
 
   // Darwin doesn't support real static executables, don't link any runtime
   // libraries with -static.
diff --git a/clang/lib/Driver/ToolChains.h b/clang/lib/Driver/ToolChains.h
index 25dae72ca86..d36a799b580 100644
--- a/clang/lib/Driver/ToolChains.h
+++ b/clang/lib/Driver/ToolChains.h
@@ -575,6 +575,8 @@ public:
   /// @name Apple ToolChain Implementation
   /// {
 
+  RuntimeLibType GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
+
   void AddLinkRuntimeLibArgs(const llvm::Triple &EffectiveTriple,
                              const llvm::opt::ArgList &Args,
                              llvm::opt::ArgStringList &CmdArgs) const override;