When compiling:
void assignMultiplyVec(double* restrict __attribute__ ((aligned (16))) a, const
double * restrict __attribute__ ((aligned (16))) b, double coef, unsigned
count) {
for(unsigned i=0; i<count; i++) {
a[i] = b[i]*coef;
}
}
Using: gcc -std=c99 -march=core2 -mtune=core2 -O3 -mfpmath=sse -ftree-vectorize
-ftree-vectorizer-verbose=9
The logs show:
essai_restrict_ref.c:2: note: Alignment of access forced using versioning.
essai_restrict_ref.c:2: note: Versioning for alignment will be applied.
essai_restrict_ref.c:2: note: Vectorizing an unaligned access.
and indeed the assembly code shows a test whether operands are 16-byte aligned.
This versioning is superfluous, since variable attributes guarantee 16-byte
alignment.
--
Summary: vectorizer ignores alignment, useless versioning
Product: gcc
Version: 4.3.2
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: David dot Monniaux at ens dot fr
GCC build triplet: i486-linux-gnu
GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38011
