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| author | Jakub Jelinek <jakub@redhat.com> | 2021-01-16 09:21:52 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2021-01-16 09:21:52 +0100 |
| commit | e2559c3945a09521ffe4f59669bc4d902ae77adb (patch) | |
| tree | 0d9e7dc7f3ca5d311e691c467152a09b234733a2 /gcc/match.pd | |
| parent | b673e7547fb95d1f0d5cd17ae9e3874742cade66 (diff) | |
| download | gcc-e2559c3945a09521ffe4f59669bc4d902ae77adb.zip gcc-e2559c3945a09521ffe4f59669bc4d902ae77adb.tar.gz gcc-e2559c3945a09521ffe4f59669bc4d902ae77adb.tar.bz2 | |
match.pd: Optimize ((cst << x) & 1) [PR96669]
While we had a ((1 << x) & 1) != 0 to x == 0 optimization already,
this patch adds ((cst << x) & 1) optimization too, this time the
second constant must be 1 though, not some power of two, but the first
one can be any constant. If it is even, the result is false, if it is
odd, the result is x == 0.
2021-01-16 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/96669
* match.pd ((CST << x) & 1 -> x == 0): New simplification.
* gcc.dg/tree-ssa/pr96669-1.c: Adjust regexp.
* gcc.dg/tree-ssa/pr96669-2.c: New test.
Diffstat (limited to 'gcc/match.pd')
| -rw-r--r-- | gcc/match.pd | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index 84c4ee6..7158e98 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -3117,6 +3117,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (op @0 { build_int_cst (TREE_TYPE (@1), low); }))))))) +/* Simplify (CST << x) & 1 to 0 if CST is even or to x == 0 if it is odd. */ +(simplify + (bit_and (lshift INTEGER_CST@1 @0) integer_onep) + (if ((wi::to_wide (@1) & 1) != 0) + (convert (eq:boolean_type_node @0 { build_zero_cst (TREE_TYPE (@0)); })) + { build_zero_cst (type); })) + /* Simplify ((C << x) & D) != 0 where C and D are power of two constants, either to false if D is smaller (unsigned comparison) than C, or to x == log2 (D) - log2 (C). Similarly for right shifts. */ |