LLVM Driver Multicall tool

This patch adds an llvm-driver multicall tool that can combine multiple
LLVM-based tools. The build infrastructure is enabled for a tool by
adding the GENERATE_DRIVER option to the add_llvm_executable CMake
call, and changing the tool's main function to a canonicalized
tool_name_main format (i.e. llvm_ar_main, clang_main, etc...).

As currently implemented llvm-driver contains dsymutil, llvm-ar,
llvm-cxxfilt, llvm-objcopy, and clang (if clang is included in the
build).

llvm-driver can be enabled from builds by setting
LLVM_TOOL_LLVM_DRIVER_BUILD=On.

There are several limitations in the current implementation, which can
be addressed in subsequent patches:

(1) the multicall binary cannot currently properly handle
multi-dispatch tools. This means symlinking llvm-ranlib to llvm-driver
will not properly result in llvm-ar's main being called.
(2) the multicall binary cannot be comprised of tools containing
conflicting cl::opt options as the global cl::opt option list cannot
contain duplicates.

These limitations can be addressed in subsequent patches.

Differential revision: https://reviews.llvm.org/D109977

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 9575e34..283dc70 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -1202,9 +1202,18 @@ Error readNativeFileToEOF(file_t FileHandle, SmallVectorImpl<char> &Buffer,
 #include "Windows/Path.inc"
 #endif
 
+bool IsLLVMDriver = false;
+
 namespace llvm {
 namespace sys {
 namespace fs {
+
+std::string getMainExecutable(const char *Argv0, void *MainAddr) {
+  if (IsLLVMDriver)
+    return sys::path::stem(Argv0).str();
+  return getMainExecutableImpl(Argv0, MainAddr);
+}
+
 TempFile::TempFile(StringRef Name, int FD)
     : TmpName(std::string(Name)), FD(FD) {}
 TempFile::TempFile(TempFile &&Other) { *this = std::move(Other); }