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| author | Roger Sayle <roger@nextmovesoftware.com> | 2020-07-28 22:55:12 +0100 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2020-07-28 22:56:24 +0100 |
| commit | 33bf56ddc6a757d2066a50dd9ce8323b379a2a0a (patch) | |
| tree | c874ed6ad71a51bca6395d031550dd4595a65a8b /gcc/fortran/parse.c | |
| parent | f3665bd1111c1799c0421490b5e655f977570354 (diff) | |
| download | gcc-33bf56ddc6a757d2066a50dd9ce8323b379a2a0a.zip gcc-33bf56ddc6a757d2066a50dd9ce8323b379a2a0a.tar.gz gcc-33bf56ddc6a757d2066a50dd9ce8323b379a2a0a.tar.bz2 | |
middle-end: Parity and popcount folding optimizations.
This patch implements several constant folding optimizations
for __builtin_parity and friends. We canonicalize popcount(x)&1
as parity(x) in gimple, and potentially convert back again when
we expand to RTL. parity(~x) is simplified to parity(x), which
is true for all integer modes with an even number of bits.
But probably most usefully, parity(x)^parity(y) can be simplified
to a parity(x^y), requiring only a single libcall or popcount.
This patch optimizes popcount and parity of an argument known to have
at most a single bit set, to be that single bit. Hence, popcount(x&8)
is simplified to (x>>3)&1. This generalizes the existing optimization
of popcount(x&1) being simplified to x&1, which is cleaned up with
this patch.
2020-07-28 Roger Sayle <roger@nextmovesoftware.com>
Richard Biener <rguenther@suse.de>
gcc/ChangeLog
* match.pd (popcount(x)&1 -> parity(x)): New simplification.
(parity(~x) -> parity(x)): New simplification.
(parity(x)^parity(y) -> parity(x^y)): New simplification.
(parity(x&1) -> x&1): New simplification.
(popcount(x) -> x>>C): New simplification.
gcc/testsuite/ChangeLog
* gcc.dg/fold-popcount-5.c: New test.
* gcc.dg/fold-parity-1.c: Likewise.
* gcc.dg/fold-parity-2.c: Likewise.
* gcc.dg/fold-parity-3.c: Likewise.
* gcc.dg/fold-parity-4.c: Likewise.
* gcc.dg/fold-parity-5.c: Likewise.
Diffstat (limited to 'gcc/fortran/parse.c')
0 files changed, 0 insertions, 0 deletions