https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71992
Bug ID: 71992
Summary: Missed BB SLP vectorization in GCC
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vekumar at gcc dot gnu.org
Target Milestone: ---
The below test case fails to vectorize.
gcc version 7.0.0 20160724 (experimental) (GCC)
gcc -Ofast -mavx -fvect-cost-model=unlimited slp.c -S -fdump-tree-slp-all
struct st
{
double x;
double y;
double z;
double p;
double q;
}*obj;
double a,b,c;
void slp_test()
{
obj->x = a*a+3.0;
obj->y= b*b+c;
obj->z= a+b*3.0;
obj->p= a+b*3.0;
obj->q =a+b+c;
}
LLVM is able to SLP vectorize looks like it is creating vector of [a,c] and
[b*3.0,b*b] and does vector add.
GCC is not SLP vectorizing. Group slitting also not working. I expected it to
get split and vectorize these statements.
obj->z= a+b*3.0;
obj->p= a+b*3.0;
Another case
struct st
{
double x;
double y;
double z;
double p;
double q;
}*obj;
double a,b,c;
void slp_test()
{
obj->x = a*b;
obj->y= b+c;
obj->z= a+b*3.0;
obj->p= a+b*3.0;
obj->q =a+b+c;
}
LLVM forms vector [b*3.0,a+b] [a,c] and does vector addition.
