Re: Gnu C compiler RTL question

Timothy Kong <>
18 Sep 1998 23:02:37 -0400

          From comp.compilers

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Re: Gnu C compiler RTL question (1998-09-18)
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From: Timothy Kong <>
Newsgroups: comp.compilers
Date: 18 Sep 1998 23:02:37 -0400
Organization: University of California, Davis
References: 98-09-034
Keywords: GCC wrote:
: I read somewhere that the RTL is independent of the machine description, but
: looking at some compiled code shows that it does depend on the registers used
: as the stack and frame pointers.

: Are thes the only instances where this occurs??

GCC RTL is machine independent in general, but the specific RTL generated
is machine-dependent. Some machine-dependent RTL features:

    - machine specific register usage:
            frame pointer, stack pointer, function return value register,
            function return pointer register

    - existence of a conditional code register, represented by cc0_rtx

    - the forms of the RTL insns generated depend on the availability of
        machine instructions; for example, this type if RTL is not generated
        for a machine with a load/store architecture:

                (set (reg ...)
                          (plus (reg ...) (mem ...)))


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