diff options
| author | Eric Botcazou <ebotcazou@adacore.com> | 2019-06-05 14:14:40 +0000 |
|---|---|---|
| committer | Eric Botcazou <ebotcazou@gcc.gnu.org> | 2019-06-05 14:14:40 +0000 |
| commit | c613138b6ce48448fa7f62dd03513d28919361d6 (patch) | |
| tree | 27268ad59c88a62106450ec1019ad35b0af6396d /gcc/fold-const.c | |
| parent | 2098f8ec2f82310104d1e3eb0a3ac0003e78600a (diff) | |
fold-const.c (extract_muldiv_1): Do not distribute a multiplication by a power-of-two value.
* fold-const.c (extract_muldiv_1) <PLUS_EXPR>: Do not distribute a
multiplication by a power-of-two value.
(fold_plusminus_mult_expr): Use pow2p_hwi to spot a power-of-two value
and turn the modulo operation into a masking operation.
From-SVN: r271963
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 3e066a2ecc4..8252cc6bb6b 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -6475,8 +6475,12 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type, apply the distributive law to commute the multiply and addition if the multiplication of the constants doesn't overflow and overflow is defined. With undefined overflow - op0 * c might overflow, while (op0 + orig_op1) * c doesn't. */ - if (code == MULT_EXPR && TYPE_OVERFLOW_WRAPS (ctype)) + op0 * c might overflow, while (op0 + orig_op1) * c doesn't. + But fold_plusminus_mult_expr would factor back any power-of-two + value so do not distribute in the first place in this case. */ + if (code == MULT_EXPR + && TYPE_OVERFLOW_WRAPS (ctype) + && !(tree_fits_shwi_p (c) && pow2p_hwi (absu_hwi (tree_to_shwi (c))))) return fold_build2 (tcode, ctype, fold_build2 (code, ctype, fold_convert (ctype, op0), @@ -7124,14 +7128,13 @@ fold_plusminus_mult_expr (location_t loc, enum tree_code code, tree type, /* No identical multiplicands; see if we can find a common power-of-two factor in non-power-of-two multiplies. This can help in multi-dimensional array access. */ - else if (tree_fits_shwi_p (arg01) - && tree_fits_shwi_p (arg11)) + else if (tree_fits_shwi_p (arg01) && tree_fits_shwi_p (arg11)) { - HOST_WIDE_INT int01, int11, tmp; + HOST_WIDE_INT int01 = tree_to_shwi (arg01); + HOST_WIDE_INT int11 = tree_to_shwi (arg11); + HOST_WIDE_INT tmp; bool swap = false; tree maybe_same; - int01 = tree_to_shwi (arg01); - int11 = tree_to_shwi (arg11); /* Move min of absolute values to int11. */ if (absu_hwi (int01) < absu_hwi (int11)) @@ -7144,7 +7147,10 @@ fold_plusminus_mult_expr (location_t loc, enum tree_code code, tree type, else maybe_same = arg11; - if (exact_log2 (absu_hwi (int11)) > 0 && int01 % int11 == 0 + const unsigned HOST_WIDE_INT factor = absu_hwi (int11); + if (factor > 1 + && pow2p_hwi (factor) + && (int01 & (factor - 1)) == 0 /* The remainder should not be a constant, otherwise we end up folding i * 4 + 2 to (i * 2 + 1) * 2 which has increased the number of multiplications necessary. */ |