Allow the number of iterations to be smaller than VF

[Christophe Lyon]

On 7 January 2018 at 21:51, James Greenhalgh <james.greenhalgh@arm.com> wrote:
> On Mon, Nov 20, 2017 at 12:12:38AM +0000, Jeff Law wrote:
>> 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
>
> The AArch64 tests are OK.
>

I've reported the failures on aarch64-none-elf -mabi=ilp32 in:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83849

Christophe

> James
>