Re: GCC beaten by ICC in stupid trig test!

[Toon Moene <toon@moene.indiv.nluug.nl>]

Joe Buck wrote:

> No.  Why would we need such a thing?  If the user does not care about
> order of evaluation, the user can write a+b+c .  As someone said, right
> now we can't tell the difference between a+b+c; if we turn it into GIMPLE
> and make t1 = a+b; 52 = t1+c; we can't tell if the user initially wrote
> (a+b)+c or a+b+c. 

This is true as far as Fortran is concerned (I cannot speak for other 
languages).

A+B+C means that the compiler could either evaluate (A+B)+C or A+(B+C) 
or (A+C)+B.

If you don't write the parentheses, you leave it up to the compiler to 
find the most convenient sequence of computations.

Dave Korn wrote:

 >   IIUIC the fact that the + operator is specified in the standard as
 > binding left-to-right imply that "a + b + c" with no brackets *has* to
 > be interpreted as "(a + b) + c".

No, it establishes the way the multi-operator expressions may be 
combined *for interpretation*.  I.e., what the expression means (on a 
high level, before applying such rules as 1.4 (6) [This standard does 
not specify] ... the method of rounding, approximating or computing 
numeric values on a particular processor").

-- 
Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
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GNU Fortran 95: http://gcc.gnu.org/fortran/ (under construction)