On Wed, 29 Jun 2011, Richard Guenther wrote:
>
> The following patch makes us handle invariant loads during vectorization.
> Dependence analysis currently isn't clever enough to disambiguate them
> thus we insert versioning-for-alias checks. For the testcase hoisting
> the load is still always possible though, and for a read-after-write
> dependence it would be possible for the vectorized loop copy as the
> may-aliasing write is varying by the scalar variable size.
>
> The existing code for vectorizing invariant accesses looks very
> suspicious - it generates a vector load at the scalar address
> to then just extract the first vector element. Huh. IMHO this
> can be simplified as done, by just re-using the scalar load result.
> But maybe this code was supposed to deal with something entirely
> different?
>
> This patch gives a 33% speedup to the phoronix himeno testcase
> if you bump the maximum alias versioning checks we want to insert.
>
> I'm currently re-bootstrapping & testing this but an earlier version
> was ok on x86_64-unknown-linux-gnu.
FYI, I'm testing the following which cures a fallout seen when
building SPEC2k6 with the committed patch. It's suboptimal for
j != 0 though - is there a way to get to the vectorized stmt
of the j == 0 iteration?
Thanks,
Richard.
2011-06-30 Richard Guenther <rguent...@suse.de>
* tree-vect-stmts.c (vectorizable_load): Remove unnecessary
assert.
Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c (revision 175709)
+++ gcc/tree-vect-stmts.c (working copy)
@@ -4574,19 +4574,14 @@ vectorizable_load (gimple stmt, gimple_s
/* 4. Handle invariant-load. */
if (inv_p && !bb_vinfo)
{
+ tree vec_inv;
+ gimple_stmt_iterator gsi2 = *gsi;
gcc_assert (!strided_load);
- if (j == 0)
- {
- tree vec_inv;
- gimple_stmt_iterator gsi2 = *gsi;
- gsi_next (&gsi2);
- vec_inv = build_vector_from_val (vectype, scalar_dest);
- new_temp = vect_init_vector (stmt, vec_inv,
- vectype, &gsi2);
- new_stmt = SSA_NAME_DEF_STMT (new_temp);
- }
- else
- gcc_unreachable (); /* FORNOW. */
+ gsi_next (&gsi2);
+ vec_inv = build_vector_from_val (vectype, scalar_dest);
+ new_temp = vect_init_vector (stmt, vec_inv,
+ vectype, &gsi2);
+ new_stmt = SSA_NAME_DEF_STMT (new_temp);
}
if (negative)
