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Re: Allow the number of iterations to be smaller than VF
- From: Jeff Law <law at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org, richard dot sandiford at linaro dot org
- Date: Sun, 19 Nov 2017 17:12:38 -0700
- Subject: Re: Allow the number of iterations to be smaller than VF
- Authentication-results: sourceware.org; auth=none
- References: <87d14hym7l.fsf@linaro.org>
On 11/17/2017 08:11 AM, Richard Sandiford wrote:
> Fully-masked loops can be profitable even if the iteration
> count is smaller than the vectorisation factor. In this case
> we're effectively doing a complete unroll followed by SLP.
>
> The documentation for min-vect-loop-bound says that the
> default value is 0, but actually the default and minimum
> were 1. We need it to be 0 for this case since the parameter
> counts a whole number of vector iterations.
>
> Tested on aarch64-linux-gnu (with and without SVE), x86_64-linux-gnu
> and powerpc64le-linux-gnu. OK to install?
>
> Richard
>
>
> 2017-11-17 Richard Sandiford <richard.sandiford@linaro.org>
> Alan Hayward <alan.hayward@arm.com>
> David Sherwood <david.sherwood@arm.com>
>
> gcc/
> * doc/sourcebuild.texi (vect_fully_masked): Document.
> * params.def (PARAM_MIN_VECT_LOOP_BOUND): Change minimum and
> default value to 0.
> * tree-vect-loop.c (vect_analyze_loop_costing): New function,
> split out from...
> (vect_analyze_loop_2): ...here. Don't check the vectorization
> factor against the number of loop iterations if the loop is
> fully-masked.
>
> gcc/testsuite/
> * lib/target-supports.exp (check_effective_target_vect_fully_masked):
> New proc.
> * gcc.dg/vect/slp-3.c: Expect all loops to be vectorized if
> vect_fully_masked.
> * gcc.target/aarch64/sve_loop_add_4.c: New test.
> * gcc.target/aarch64/sve_loop_add_4_run.c: Likewise.
> * gcc.target/aarch64/sve_loop_add_5.c: Likewise.
> * gcc.target/aarch64/sve_loop_add_5_run.c: Likewise.
> * gcc.target/aarch64/sve_miniloop_1.c: Likewise.
> * gcc.target/aarch64/sve_miniloop_2.c: Likewise.
OK.
Jeff