This is the mail archive of the
gcc-cvs@gcc.gnu.org
mailing list for the GCC project.
r262961 - in /trunk/gcc: ChangeLog hwint.c
- From: rsandifo at gcc dot gnu dot org
- To: gcc-cvs at gcc dot gnu dot org
- Date: Wed, 25 Jul 2018 08:41:36 -0000
- Subject: r262961 - in /trunk/gcc: ChangeLog hwint.c
Author: rsandifo
Date: Wed Jul 25 08:41:35 2018
New Revision: 262961
URL: https://gcc.gnu.org/viewcvs?rev=262961&root=gcc&view=rev
Log:
Fix ceil_log2(0) (PR 86644)
This PR shows a pathological case in which we try SLP vectorisation on
dead code. We record that 0 bits of the result are enough to satisfy
all users (which is true), and that led to precision being 0 in:
static unsigned int
vect_element_precision (unsigned int precision)
{
precision = 1 << ceil_log2 (precision);
return MAX (precision, BITS_PER_UNIT);
}
ceil_log2 (0) returned 64 rather than 0, leading to 1 << 64, which is UB.
2018-07-25 Richard Sandiford <richard.sandiford@arm.com>
gcc/
* hwint.c (ceil_log2): Fix comment. Return 0 for 0.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/hwint.c