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Enable vectorization for unknown tripcount in very cheap cost model but disable epilog vectorization.

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gcc/ChangeLog:

	* tree-vect-loop.cc (vect_analyze_loop_costing): Enable
	vectorization for LOOP_VINFO_PEELING_FOR_NITER in very cheap
	cost model.
	(vect_analyze_loop): Disable epilogue vectorization in very
	cheap cost model.
	* doc/invoke.texi: Adjust documents for very-cheap cost model.
This commit is contained in:
liuhongt 2024-03-25 21:28:14 -07:00
parent c8957c8779
commit 70c3db511b
2 changed files with 7 additions and 10 deletions
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11
gcc/doc/invoke.texi
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@ -14315,13 +14315,10 @@ counts that will likely execute faster than when executing the original
scalar loop. The @samp{cheap} model disables vectorization of
loops where doing so would be cost prohibitive for example due to
required runtime checks for data dependence or alignment but otherwise
is equal to the @samp{dynamic} model. The @samp{very-cheap} model only
allows vectorization if the vector code would entirely replace the
scalar code that is being vectorized. For example, if each iteration
of a vectorized loop would only be able to handle exactly four iterations
of the scalar loop, the @samp{very-cheap} model would only allow
vectorization if the scalar iteration count is known to be a multiple
of four.
is equal to the @samp{dynamic} model. The @samp{very-cheap} model disables
vectorization of loops when any runtime check for data dependence or alignment
is required, it also disables vectorization of epilogue loops but otherwise is
equal to the @samp{cheap} model.
The default cost model depends on other optimization flags and is
either @samp{dynamic} or @samp{cheap}.

6
gcc/tree-vect-loop.cc
View file

@ -2375,8 +2375,7 @@ vect_analyze_loop_costing (loop_vec_info loop_vinfo,
a copy of the scalar code (even if we might be able to vectorize it). */
if (loop_cost_model (loop) == VECT_COST_MODEL_VERY_CHEAP
&& (LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo)
|| LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo)
|| LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo)))
|| LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo)))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
@ -3683,7 +3682,8 @@ vect_analyze_loop (class loop *loop, gimple *loop_vectorized_call,
/* No code motion support for multiple epilogues so for now
not supported when multiple exits. */
&& !LOOP_VINFO_EARLY_BREAKS (first_loop_vinfo)
&& !loop->simduid);
&& !loop->simduid
&& loop_cost_model (loop) > VECT_COST_MODEL_VERY_CHEAP);
if (!vect_epilogues)
return first_loop_vinfo;