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[Bug middle-end/30364] [4.1/4.2/4.3 Regression] Wrong variable ranges due to constant folding
- From: "gdr at integrable-solutions dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 5 Jan 2007 21:06:43 -0000
- Subject: [Bug middle-end/30364] [4.1/4.2/4.3 Regression] Wrong variable ranges due to constant folding
- References: <bug-30364-7904@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #8 from gdr at integrable-solutions dot net 2007-01-05 21:06 -------
Subject: Re: [4.1/4.2/4.3 Regression] Wrong variable ranges due to constant
folding
"jakub at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:
| Do the parenthesis matter in C?
Yes, see paragraphes 11 dowward in the section 5.1.2.3.
| They do matter in say Fortran, but in C I
| think
| (a - 20) + (b - 20) can be evaluated as (a + b) + (-20 + -20) or a - 20 - 20
+
| b
while that is permitted by the fortran standard, it is my understanding
that *existing* practice has fortran compilers refrain from messing
with parenthesis.
However, this has become a middle-end issue; so I guess I must voice
the concern for languages where unconditional re-association is not
permitted. The C and C++ languages are example of those.
-- Gaby
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30364