https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65951
Bug ID: 65951
Summary: [AArch64] Will not vectorize multiplication by long
constant
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: alalaw01 at gcc dot gnu.org
Target Milestone: ---
Target: aarch64
This loop:
void
foo (long *arr)
{
for (int i = 0; i < 256; i++)
arr[i] *= 19594L;
}
will not vectorize on AArch64, but does on x86. On AArch64,
-fdump-tree-vect-details reveals:
test.c:4:3: note: ==> examining statement: _9 = _8 * 19594;
test.c:4:3: note: vect_is_simple_use: operand _8
test.c:4:3: note: def_stmt: _8 = *_7;
test.c:4:3: note: type of def: 3.
test.c:4:3: note: vect_is_simple_use: operand 19594
test.c:4:3: note: op not supported by target.
test.c:4:3: note: not vectorized: relevant stmt not supported: _9 = _8 * 19594;
on x86, vectorization fails with vectorization_factor = 4 (V4DI), but succeeds
at V2DI.
We could vectorize this on AArch64 even if we have to perform a
multiple-instruction load of that constant (invariant!) before the
loop...right?
