The following fixes the computation of supports_partial_vectors which
is used to prune the set of modes to iterate over for epilog
vectorization. The used partial_vectors_supported_p predicate
only looks for while_ult while also support predication when
mask modes are integer modes as for AVX512.
I've noticed this isn't very effective on x86_64 anyway since
if the main loop mode is autodetected we skip re-analyzing
mode_i == 0, but then mode_i == 1 is usually the very same
large mode.
Thus I do wonder if we should instead always (or when
--param vect-partial-vector-usage != 0, or when the target would
support predication in principle) perform main loop analysis
with partial vectors in mind (start with can_use_partial_vectors_p =
true), but only at the end honor the --param when deciding on
using_partial_vectors_p. We can then remember can_use_partial_vectors_p
for each analyzed mode and use that more specific info for the
pruning? For the missed skipping we probably want to increment
mode_i based on vect_chooses_same_modes_p, like we do in
vect_analyze_loop_1. I'll propose a patch for this - but this
would regress --param vect-partial-vector-usage=1 on x86 without
the patch below.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
OK?
* tree-vect-loop.cc (vect_analyze_loop): Consider AVX512
style masking when computing supports_partial_vectors.
---
gcc/tree-vect-loop.cc | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index c824b5abaaf..b91ef4a2325 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -3742,8 +3742,15 @@ vect_analyze_loop (class loop *loop, gimple
*loop_vectorized_call,
vector_modes[0] = autodetected_vector_mode;
mode_i = 0;
- bool supports_partial_vectors =
- partial_vectors_supported_p () && param_vect_partial_vector_usage != 0;
+ bool supports_partial_vectors = param_vect_partial_vector_usage != 0;
+ machine_mode mask_mode;
+ if (supports_partial_vectors
+ && !partial_vectors_supported_p ()
+ && !(VECTOR_MODE_P (first_loop_vinfo->vector_mode)
+ && targetm.vectorize.get_mask_mode
+ (first_loop_vinfo->vector_mode).exists (&mask_mode)
+ && SCALAR_INT_MODE_P (mask_mode)))
+ supports_partial_vectors = false;
poly_uint64 first_vinfo_vf = LOOP_VINFO_VECT_FACTOR (first_loop_vinfo);
loop_vec_info orig_loop_vinfo = first_loop_vinfo;
--
2.43.0
