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Re: rtl semantics


Ian Lance Taylor wrote:
Russell Shaw <rjshaw@netspace.net.au> writes:


Are the templates in <machine>.md real RTL, or only templates used to generate RTL?
Is "RTL" a textual language, or just some C struct?


I don't think anybody has bothered to define the terms formally.  RTL
is both a text language and a C struct.  The text language appears in
the .md files and in debugging dumps.  The C struct is defined in
rtl.h.  Which one is meant by "RTL" has to be determined by context.

Note that not all information about the compiled code is represented
in RTL.

gcc is not an academic exercise which can be described usefully in
formal terms.  It is a large untidy body of working code.  RTL is an
important concept used in various ways to represent the compiled
program in terms of the instruction set supported by a specific
processor.

Besides the internals manual, you may find some helpful hints at the
gcc wiki:
    http://www.dberlin.org/gccwiki/

I understand now the format in rtl.def and how the fields are stripped out with cpp. It makes more sense now after reading some .md files too.


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