VEC_COND_EXPR optimizations v2
Marc Glisse
marc.glisse@inria.fr
Wed Aug 5 13:32:32 GMT 2020
New version that passed bootstrap+regtest during the night.
When vector comparisons were forced to use vec_cond_expr, we lost a number of
optimizations (my fault for not adding enough testcases to prevent that).
This patch tries to unwrap vec_cond_expr a bit so some optimizations can
still happen.
I wasn't planning to add all those transformations together, but adding one
caused a regression, whose fix introduced a second regression, etc.
Restricting to constant folding would not be sufficient, we also need at
least things like X|0 or X&X. The transformations are quite conservative
with :s and folding only if everything simplifies, we may want to relax
this later. And of course we are going to miss things like a?b:c + a?c:b
-> b+c.
In terms of number of operations, some transformations turning 2
VEC_COND_EXPR into VEC_COND_EXPR + BIT_IOR_EXPR + BIT_NOT_EXPR might not look
like a gain... I expect the bit_not disappears in most cases, and
VEC_COND_EXPR looks more costly than a simpler BIT_IOR_EXPR.
I am a bit confused that with avx512 we get types like "vector(4)
<signed-boolean:2>" with :2 and not :1 (is it a hack so true is 1 and not
-1?), but that doesn't matter for this patch.
2020-08-05 Marc Glisse <marc.glisse@inria.fr>
PR tree-optimization/95906
PR target/70314
* match.pd ((c ? a : b) op d, (c ? a : b) op (c ? d : e),
(v ? w : 0) ? a : b, c1 ? c2 ? a : b : b): New transformations.
(op (c ? a : b)): Update to match the new transformations.
* gcc.dg/tree-ssa/andnot-2.c: New file.
* gcc.dg/tree-ssa/pr95906.c: Likewise.
* gcc.target/i386/pr70314.c: Likewise.
--
Marc Glisse
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