On 10/28/2009 06:24 AM, Kevin Kofler wrote:
Jud Craft wrote:
On Mon, Oct 26, 2009 at 12:31 PM, Kevin Kofler wrote:
But this is about C++.
I don't mean to misunderstand, but if I recall from your very first
post in this thread...
Actually, the ABI issue is only if you use the C code generator, not the
native ones.
Hence I thought you were talking about ABI issues with C.
You misunderstood me. The C code generator is an LLVM *back*end, not a
frontend. The frontend is what recognizes the input language, the backend is
what defines the output LLVM generates.
I'm not up on how LLVM frontend integration works, so I actually don't
understand the distinction between "the LLVM C Backend" and "the
native LLVM backends".
LLVM can either directly output machine code (native backend) for some
architectures or it can output preoptimized C code (especially for those
architectures which don't have a native backend). The latter is what the "C
code generator" or "C backend" does.
clang and all other LLVM language front-ends produce "bitcode", which is
virtualized machine code a la JVM. LLVM backend generates
processor-dependent machine code from processor-independent machine code.
The LLVM C __backend__ converts bitcode back into C... something no
idiot in their right mind would use for C++ or anything else. The LLVM
C backend is not commonly used.
The vast, vast majority of people trying to compile C++ programs with
LLVM would either use
clang -> llvm -> asm code
or
llvm-gcc -> llvm -> asm code
Certainly not
Clang (C++) → LLVM → LLVM C backend → gcc [-> asm code]
Regards,
Jeff
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