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Re: /internet
- To: moshier at mediaone dot net
- Subject: Re: /internet
- From: Craig Burley <burley at gnu dot org>
- Date: Wed, 16 Dec 1998 12:37:01 -0500 (EST)
- CC: tprince at cat dot e-mail dot com, bosch at gnat dot com, egcs at cygnus dot com, hjstein at bfr dot co dot il, jbuck at Synopsys dot COM
>There has been general agreement that gcc is not supposed to make
>optimizations that could change the value of an expression.
>Associative law optimizations of floating-point expressions certainly
>can change the value and they should continue to be disallowed. Users
>should not have to fear that gcc is going to take arbitrary liberties
>and rewrite their programs for them without very explicit permission.
Even if this was true -- and IMO it isn't -- it doesn't apply to well-
designed numerical-processing languages like Fortran, in which it
is quite clear that A*B*C*D can be evaluated as (D*A)*(C*B), for
example.
Therefore, we should make the *back end* work properly in a language-
independent sense. If people want the gcc to produce slower code
than g77, that's okay -- they can have gcc explicitly group the
operations for consumption by the back end, something Fortran doesn't
generally need to do.
tq vm, (burley)