[PATCH] D25338: [Driver] Make -print-libgcc-file-name print compiler-rt lib when used

[Michał Górny via cfe-commits]

mgorny created this revision.
mgorny added a reviewer: ddunbar.
mgorny added a subscriber: cfe-commits.
Herald added a subscriber: dberris.

Make the -print-libgcc-file-name option print an appropriate compiler
runtime library, that is libgcc.a if gcc runtime is used
and an appropriate compiler-rt library if that runtime is used.

The main use for this is to allow linking executables built with
-nodefaultlibs (e.g. to avoid linking to the standard C++ library) to
the compiler runtime library, e.g. using:

  clang++ ... -nodefaultlibs $(clang++ ... -print-libgcc-file-name)

in which case currently a program built like this linked to the gcc
runtime unconditionally. The patch fixes it to use compiler-rt libraries
instead when compiler-rt is the active runtime.


https://reviews.llvm.org/D25338

Files:
  docs/CommandGuide/clang.rst
  include/clang/Driver/Options.td
  lib/Driver/Driver.cpp


Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -994,7 +994,15 @@
   }
 
   if (C.getArgs().hasArg(options::OPT_print_libgcc_file_name)) {
-    llvm::outs() << GetFilePath("libgcc.a", TC) << "\n";
+    ToolChain::RuntimeLibType RLT = TC.GetRuntimeLibType(C.getArgs());
+    switch (RLT) {
+    case ToolChain::RLT_CompilerRT:
+      llvm::outs() << TC.getCompilerRTArgString(C.getArgs(), "builtins") << "\n";
+      break;
+    case ToolChain::RLT_Libgcc:
+      llvm::outs() << GetFilePath("libgcc.a", TC) << "\n";
+      break;
+    }
     return false;
   }
 
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1861,7 +1861,8 @@
 def print_ivar_layout : Flag<["-"], "print-ivar-layout">, Flags<[CC1Option]>,
   HelpText<"Enable Objective-C Ivar layout bitmap print trace">;
 def print_libgcc_file_name : Flag<["-", "--"], "print-libgcc-file-name">,
-  HelpText<"Print the library path for \"libgcc.a\"">;
+  HelpText<"Print the library path for the currently used compiler runtime "
+           "library (\"libgcc.a\" or \"libclang_rt.builtins.*.a\" appropriately)">;
 def print_multi_directory : Flag<["-", "--"], "print-multi-directory">;
 def print_multi_lib : Flag<["-", "--"], "print-multi-lib">;
 def print_multi_os_directory : Flag<["-", "--"], "print-multi-os-directory">,
Index: docs/CommandGuide/clang.rst
===================================================================
--- docs/CommandGuide/clang.rst
+++ docs/CommandGuide/clang.rst
@@ -394,7 +394,8 @@
 
 .. option:: -print-libgcc-file-name
 
-  Print the library path for "libgcc.a".
+  Print the library path for the currently used compiler runtime library
+  ("libgcc.a" or "libclang_rt.builtins.*.a" appropriately).
 
 .. option:: -print-prog-name=<name>
 


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