diff options
| author | Richard Henderson <rth@cygnus.com> | 2000-05-29 00:40:51 -0700 |
|---|---|---|
| committer | Richard Henderson <rth@gcc.gnu.org> | 2000-05-29 00:40:51 -0700 |
| commit | d41638e4c5e0ad186c72cc8af1786b5319c684f6 (patch) | |
| tree | b2aed1ebcca2488360c1ebd0d03f0c01bbc73d10 /gcc/combine.c | |
| parent | 085f17143f3444e9fedce6501e21d28bedac8702 (diff) | |
| download | gcc-d41638e4c5e0ad186c72cc8af1786b5319c684f6.zip gcc-d41638e4c5e0ad186c72cc8af1786b5319c684f6.tar.gz gcc-d41638e4c5e0ad186c72cc8af1786b5319c684f6.tar.bz2 | |
combine.c (force_to_mode): Convert subtraction from a constant to NEG or NOT when conditions allow.
* combine.c (force_to_mode) [MINUS]: Convert subtraction from
a constant to NEG or NOT when conditions allow.
From-SVN: r34248
Diffstat (limited to 'gcc/combine.c')
| -rw-r--r-- | gcc/combine.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index d4af90e..47642f3 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -6846,7 +6846,6 @@ force_to_mode (x, mode, mask, reg, just_select) /* ... fall through ... */ - case MINUS: case MULT: /* For PLUS, MINUS and MULT, we need any bits less significant than the most significant bit in MASK since carries from those bits will @@ -6854,6 +6853,28 @@ force_to_mode (x, mode, mask, reg, just_select) mask = fuller_mask; goto binop; + case MINUS: + /* If X is (minus C Y) where C's least set bit is larger than any bit + in the mask, then we may replace with (neg Y). */ + if (GET_CODE (XEXP (x, 0)) == CONST_INT + && (INTVAL (XEXP (x, 0)) & -INTVAL (XEXP (x, 0))) > mask) + { + x = gen_unary (NEG, GET_MODE (x), GET_MODE (x), XEXP (x, 1)); + return force_to_mode (x, mode, mask, reg, next_select); + } + + /* Similarly, if C contains every bit in the mask, then we may + replace with (not Y). */ + if (GET_CODE (XEXP (x, 0)) == CONST_INT + && (INTVAL (XEXP (x, 0)) | mask) == INTVAL (XEXP (x, 0))) + { + x = gen_unary (NOT, GET_MODE (x), GET_MODE (x), XEXP (x, 1)); + return force_to_mode (x, mode, mask, reg, next_select); + } + + mask = fuller_mask; + goto binop; + case IOR: case XOR: /* If X is (ior (lshiftrt FOO C1) C2), try to commute the IOR and |