| Message ID | aa1b1f0d-95c9-ce18-352d-582799302e2d@codesourcery.com |
|---|---|
| State | New |
| Headers | show |
| Series | vect: Try smaller vector size when SLP split fails | expand |
On Wed, Aug 5, 2020 at 3:30 PM Andrew Stubbs <ams@codesourcery.com> wrote: > > This patch improves SLP performance in combination with some patches I > have in development to add multiple vector sizes to amdgcn. > > The problem is that amdgcn's preferred vector size has 64 lanes, and SLP > does not support lane masking. My patches will add smaller vector sizes > (32, 16, 8, 4, 2) which make the lane masking implicit, but still SLP > doesn't use them; it simply rejects the first size it sees and gives up. > > This patch detects the rejection early and looks to see if there is a > smaller, more suitable vector size. The result is many more successful > SLP testcases. > > OK to commit? (I have an x86_64 bootstrap and test in progress.) Is this about basic-block SLP? There it should eventually split groups. For loop based SLP did you specify the autovectorize_vector_modes hook? Otherwise the vectorizer only tries a single size. Richard. > Andrew
vect: Try smaller vector size when SLP split fails If the preferred vector size is larger than can be used then try again with a smaller size. This allows SLP to work more effectively on targets with very large vectors. gcc/ChangeLog: * tree-vect-slp.c (vect_analyze_slp_instance): Reduce vector size if the default mode is too large. diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c index 72192b5a813..95518a263c7 100644 --- a/gcc/tree-vect-slp.c +++ b/gcc/tree-vect-slp.c @@ -2367,6 +2367,16 @@ vect_analyze_slp_instance (vec_info *vinfo, for (i = 0; i < group_size; i++) if (!matches[i]) break; + if (i > 1 && i < group_size && i < const_nunits && scalar_type) + { + tree vec = get_vectype_for_scalar_type (vinfo, scalar_type, i); + if (vec) + { + nunits = TYPE_VECTOR_SUBPARTS (vec); + const_nunits = nunits.to_constant (); + } + } + if (i >= const_nunits && i < group_size) { /* Split into two groups at the first vector boundary before i. */