http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58135
Bug ID: 58135
Summary: [x86] Missed opportunities for partial SLP
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ysrumyan at gmail dot com
If we consider the following simple test-case
int a[100];
void foo()
{
a[0] = a[1] = a[2] = a[3] = 0;
}
SLP vectorization of basic block takes place:
gcc -S -O3 -m32 t.c -ftree-vectorizer-verbose=1
t.c:4: note: Vectorized basic-block
but if we add at least one more assignment it won't be vectorized:
a[0] = a[1] = a[2] = a[3] = a[4] = 0;
t11.c:4: note: Build SLP failed: unrolling required in basic block SLP
It is clear that gcc can do partial BB vectorization, i.e. vectorize the first
4 assignments only.
