rs6000: Support variable insert and Expand vec_insert in expander [PR79251]
vec_insert accepts 3 arguments, arg0 is input vector, arg1 is the value
to be insert, arg2 is the place to insert arg1 to arg0. Current expander
generates stxv+stwx+lxv if arg2 is variable instead of constant, which
causes serious store hit load performance issue on Power. This patch tries
1) Build VIEW_CONVERT_EXPR for vec_insert (i, v, n) like v[n&3] = i to
unify the gimple code, then expander could use vec_set_optab to expand.
2) Expand the IFN VEC_SET to fast instructions: lvsr+insert+lvsl.
In this way, "vec_insert (i, v, n)" and "v[n&3] = i" won't be expanded too
early in gimple stage if arg2 is variable, avoid generating store hit load
instructions.
Though instructions increase from 5 to 7, the performance is improved
60% in typical cases.
Tested with V2DI, V2DF V4SI, V4SF, V8HI, V16QI on Power9-LE.
2021-01-22 Xionghu Luo <luoxhu@linux.ibm.com>
gcc/ChangeLog:
PR target/79251
PR target/98065
* config/rs6000/rs6000-c.c (altivec_resolve_overloaded_builtin):
Ajdust variable index vec_insert from address dereference to
ARRAY_REF(VIEW_CONVERT_EXPR) tree expression.
* config/rs6000/rs6000-protos.h (rs6000_expand_vector_set_var):
New declaration.
* config/rs6000/rs6000.c (rs6000_expand_vector_set_var): New function.
2021-01-22 Xionghu Luo <luoxhu@linux.ibm.com>
gcc/testsuite/ChangeLog:
* gcc.target/powerpc/pr79251.p9.c: New test.
* gcc.target/powerpc/pr79251-run.c: New test.
* gcc.target/powerpc/pr79251.h: New header.