Return to the
comp.compilers page.
Search the
comp.compilers archives again.
| Related articles |
|---|
| [5 earlier articles] |
| Re: Optimization techniques 847-115-0292@kylheku.com (Kaz Kylheku) (2019-04-19) |
| Re: Optimization techniques rick.c.hodgin@gmail.com (Rick C. Hodgin) (2019-04-19) |
| Re: Optimization techniques gneuner2@comcast.net (George Neuner) (2019-04-19) |
| Re: Optimization techniques DrDiettrich1@netscape.net (Hans-Peter Diettrich) (2019-04-20) |
| Re: Optimization techniques rick.c.hodgin@gmail.com (Rick C. Hodgin) (2019-04-19) |
| Re: Optimization techniques DrDiettrich1@netscape.net (Hans-Peter Diettrich) (2019-04-20) |
| Re: Optimization techniques gneuner2@comcast.net (George Neuner) (2019-04-20) |
| Re: Optimization techniques david.brown@hesbynett.no (David Brown) (2019-04-23) |
| Re: Optimization techniques david.brown@hesbynett.no (David Brown) (2019-04-23) |
| Re: Optimization techniques david.brown@hesbynett.no (David Brown) (2019-04-23) |
| Re: Optimization techniques rick.c.hodgin@gmail.com (Rick C. Hodgin) (2019-04-24) |
| Re: Optimization techniques martin@gkc.org.uk (Martin Ward) (2019-04-25) |
| Re: Optimization techniques david.brown@hesbynett.no (David Brown) (2019-04-25) |
| [23 later articles] |
| From: | George Neuner <gneuner2@comcast.net> |
| Newsgroups: | comp.compilers |
| Date: | Sat, 20 Apr 2019 18:59:45 -0400 |
| Organization: | A noiseless patient Spider |
| References: | 19-04-004 19-04-012 |
| Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="28068"; mail-complaints-to="abuse@iecc.com" |
| Keywords: | C, optimize |
| Posted-Date: | 20 Apr 2019 22:36:09 EDT |
On Sat, 20 Apr 2019 00:27:11 +0200, Hans-Peter Diettrich
<DrDiettrich1@netscape.net> wrote:
>I'm always a bit sceptic when C/C++ and "safe" occur in the same
>sentence. AFAIR a C compiler is allowed to ignore parentheses when
>reordering expressions, what can lead to numeric instabilities.
By the standard, a C compiler IS required to respect parentheses
within an arithmetic expression. But even fully parenthesized
expressions contain subexpressions whose evaluations can be reordered.
e.g., (a + (b + c)) has to be equivalent to
t1 = b + c
t2 = a + t1
but if any of a, b, or c is an expression itself - e.g., a pointer
dereference - the parenthesized expression does not imply any ordering
of *their* individual evaluations.
George
Return to the
comp.compilers page.
Search the
comp.compilers archives again.