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* [Bug middle-end/37780] Conditional expression with __builtin_clz() should be optimized out
[not found] <bug-37780-4@http.gcc.gnu.org/bugzilla/>
@ 2012-03-20 8:31 ` amker.cheng at gmail dot com
0 siblings, 0 replies; 2+ messages in thread
From: amker.cheng at gmail dot com @ 2012-03-20 8:31 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37780
--- Comment #2 from amker.cheng <amker.cheng at gmail dot com> 2012-03-20 07:58:09 UTC ---
the special case could be easily detected when gimplifying.
but actually I am not sure whether it can be done even in middle end, since the
middle end should not depend on any target information, like
CLZ_DEFINED_VALUE_AT_ZERO, right?
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug middle-end/37780] Conditional expression with __builtin_clz() should be optimized out
2008-10-09 7:13 [Bug fortran/37780] New: Optimize LEADZ/TRAILZ for zero arguments burnus at gcc dot gnu dot org
@ 2009-03-28 16:33 ` fxcoudert at gcc dot gnu dot org
0 siblings, 0 replies; 2+ messages in thread
From: fxcoudert at gcc dot gnu dot org @ 2009-03-28 16:33 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from fxcoudert at gcc dot gnu dot org 2009-03-28 16:33 -------
This is not a Fortran issue, it should be done in the middle-end. On platforms
that have a defined value for __builtin_clz(0), the conditional in the function
below should be optimized out:
int foo (int i)
{
return (i == 0) ? sizeof (int) * 8 : __builtin_clz (i);
}
Targets where this is expected to be an issue are: alpha, cris, rs6000, m68k,
arm and s390.
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Component|fortran |middle-end
Ever Confirmed|0 |1
GCC target triplet| |CLZ_DEFINED_VALUE_AT_ZERO !=
| |0
Last reconfirmed|0000-00-00 00:00:00 |2009-03-28 16:33:36
date| |
Summary|Optimize LEADZ/TRAILZ for |Conditional expression with
|zero arguments |__builtin_clz() should be
| |optimized out
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37780
^ permalink raw reply [flat|nested] 2+ messages in thread
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[not found] <bug-37780-4@http.gcc.gnu.org/bugzilla/>
2012-03-20 8:31 ` [Bug middle-end/37780] Conditional expression with __builtin_clz() should be optimized out amker.cheng at gmail dot com
2008-10-09 7:13 [Bug fortran/37780] New: Optimize LEADZ/TRAILZ for zero arguments burnus at gcc dot gnu dot org
2009-03-28 16:33 ` [Bug middle-end/37780] Conditional expression with __builtin_clz() should be optimized out fxcoudert at gcc dot gnu dot org
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