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[AArch64][1/5] Reimplement aarch64_bitmask_imm 

2015-09-20  Wilco Dijkstra  <wdijkstr@arm.com>

	* config/aarch64/aarch64.c (aarch64_bitmask_imm): Reimplement using
	faster algorithm.

From-SVN: r227946
This commit is contained in:
Wilco Dijkstra 2015-09-20 16:34:44 +00:00 committed by Jiong Wang
parent e4bdea2f30
commit a64c73a2f0
2 changed files with 58 additions and 9 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2015-09-20 Wilco Dijkstra <wdijkstr@arm.com>
* config/aarch64/aarch64.c (aarch64_bitmask_imm): Reimplement using
faster algorithm.
2015-09-20 Jeff Law <law@redhat.com>
PR tree-optimization/47679

62
gcc/config/aarch64/aarch64.c
View File

@ -3405,19 +3405,63 @@ aarch64_movw_imm (HOST_WIDE_INT val, machine_mode mode)
|| (val & (((HOST_WIDE_INT) 0xffff) << 16)) == val);
}
/* Multipliers for repeating bitmasks of width 32, 16, 8, 4, and 2. */
static const unsigned HOST_WIDE_INT bitmask_imm_mul[] =
{
0x0000000100000001ull,
0x0001000100010001ull,
0x0101010101010101ull,
0x1111111111111111ull,
0x5555555555555555ull,
};
/* Return true if val is a valid bitmask immediate. */
bool
aarch64_bitmask_imm (HOST_WIDE_INT val, machine_mode mode)
aarch64_bitmask_imm (HOST_WIDE_INT val_in, machine_mode mode)
{
if (GET_MODE_SIZE (mode) < 8)
{
/* Replicate bit pattern. */
val &= (HOST_WIDE_INT) 0xffffffff;
val |= val << 32;
}
return bsearch (&val, aarch64_bitmasks, AARCH64_NUM_BITMASKS,
sizeof (aarch64_bitmasks[0]), aarch64_bitmasks_cmp) != NULL;
unsigned HOST_WIDE_INT val, tmp, mask, first_one, next_one;
int bits;
/* Check for a single sequence of one bits and return quickly if so.
The special cases of all ones and all zeroes returns false. */
val = (unsigned HOST_WIDE_INT) val_in;
tmp = val + (val & -val);
if (tmp == (tmp & -tmp))
return (val + 1) > 1;
/* Replicate 32-bit immediates so we can treat them as 64-bit. */
if (mode == SImode)
val = (val << 32) | (val & 0xffffffff);
/* Invert if the immediate doesn't start with a zero bit - this means we
only need to search for sequences of one bits. */
if (val & 1)
val = ~val;
/* Find the first set bit and set tmp to val with the first sequence of one
bits removed. Return success if there is a single sequence of ones. */
first_one = val & -val;
tmp = val & (val + first_one);
if (tmp == 0)
return true;
/* Find the next set bit and compute the difference in bit position. */
next_one = tmp & -tmp;
bits = clz_hwi (first_one) - clz_hwi (next_one);
mask = val ^ tmp;
/* Check the bit position difference is a power of 2, and that the first
sequence of one bits fits within 'bits' bits. */
if ((mask >> bits) != 0 || bits != (bits & -bits))
return false;
/* Check the sequence of one bits is repeated 64/bits times. */
return val == mask * bitmask_imm_mul[__builtin_clz (bits) - 26];
}