diff options
| author | Jim Wilson <wilson@gcc.gnu.org> | 1994-08-05 09:29:21 -0700 |
|---|---|---|
| committer | Jim Wilson <wilson@gcc.gnu.org> | 1994-08-05 09:29:21 -0700 |
| commit | ceb1d26880ef6ccf4528f8e11ba611c0ff886933 (patch) | |
| tree | 20dac1162c756f8be897ccfe4f72b9b331490c2f | |
| parent | 976ef4f727499247c733bf00b357efba0ffaa288 (diff) | |
| download | gcc-ceb1d26880ef6ccf4528f8e11ba611c0ff886933.zip gcc-ceb1d26880ef6ccf4528f8e11ba611c0ff886933.tar.gz gcc-ceb1d26880ef6ccf4528f8e11ba611c0ff886933.tar.bz2 | |
(expand_mult): Accept DImode for synth_mult only if CONST_DOUBLE_HIGH is zero.
(expand_mult): Accept DImode for synth_mult only if
CONST_DOUBLE_HIGH is zero. Reject negative values for synth_mult
if the mode is larger than HOST_BITS_PER_INT. Don't do the
negate_variant if the mode is larger than HOST_BITS_PER_INT.
From-SVN: r7860
| -rw-r--r-- | gcc/expmed.c | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/gcc/expmed.c b/gcc/expmed.c index 46e16be..ab685ea 100644 --- a/gcc/expmed.c +++ b/gcc/expmed.c @@ -2062,23 +2062,31 @@ expand_mult (mode, op0, op1, target, unsignedp) { rtx const_op1 = op1; + /* synth_mult does an `unsigned int' multiply. As long as the mode is + less than or equal in size to `unsigned int' this doesn't matter. + If the mode is larger than `unsigned int', then synth_mult works only + if the constant value exactly fits in an `unsigned int' without any + truncation. This means that multiplying by negative values does + not work; results are off by 2^32 on a 32 bit machine. */ + /* If we are multiplying in DImode, it may still be a win to try to work with shifts and adds. */ if (GET_CODE (op1) == CONST_DOUBLE && GET_MODE_CLASS (GET_MODE (op1)) == MODE_INT - && HOST_BITS_PER_INT <= BITS_PER_WORD) - { - if ((CONST_DOUBLE_HIGH (op1) == 0 && CONST_DOUBLE_LOW (op1) >= 0) - || (CONST_DOUBLE_HIGH (op1) == -1 && CONST_DOUBLE_LOW (op1) < 0)) - const_op1 = GEN_INT (CONST_DOUBLE_LOW (op1)); - } + && HOST_BITS_PER_INT >= BITS_PER_WORD + && CONST_DOUBLE_HIGH (op1) == 0) + const_op1 = GEN_INT (CONST_DOUBLE_LOW (op1)); + else if (HOST_BITS_PER_INT < GET_MODE_BITSIZE (mode) + && GET_CODE (op1) == CONST_INT + && INTVAL (op1) < 0) + const_op1 = 0; /* We used to test optimize here, on the grounds that it's better to produce a smaller program when -O is not used. But this causes such a terrible slowdown sometimes that it seems better to use synth_mult always. */ - if (GET_CODE (const_op1) == CONST_INT) + if (const_op1 && GET_CODE (const_op1) == CONST_INT) { struct algorithm alg; struct algorithm alg2; @@ -2096,10 +2104,16 @@ expand_mult (mode, op0, op1, target, unsignedp) mult_cost = MIN (12 * add_cost, mult_cost); synth_mult (&alg, val, mult_cost); - synth_mult (&alg2, - val, - (alg.cost < mult_cost ? alg.cost : mult_cost) - negate_cost); - if (alg2.cost + negate_cost < alg.cost) - alg = alg2, variant = negate_variant; + + /* This works only if the inverted value actually fits in an + `unsigned int' */ + if (HOST_BITS_PER_INT >= GET_MODE_BITSIZE (mode)) + { + synth_mult (&alg2, - val, + (alg.cost < mult_cost ? alg.cost : mult_cost) - negate_cost); + if (alg2.cost + negate_cost < alg.cost) + alg = alg2, variant = negate_variant; + } /* This proves very useful for division-by-constant. */ synth_mult (&alg2, val - 1, |