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| author | Rich Felker <dalias@aerifal.cx> | 2012-04-11 14:11:47 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2012-04-11 14:11:47 -0400 |
| commit | 1bdd5c8b9868ebc092074e078604acb80546e43f (patch) | |
| tree | a9d2120c543db826cc9c30c902b62bd23267c10a /src/internal | |
| parent | 7ef1a9bba56aa756d8166c4c93cf4a178d6c0c0c (diff) | |
| download | musl-1bdd5c8b9868ebc092074e078604acb80546e43f.tar.gz | |
optimize floatscan: avoid excessive upscaling
upscaling by even one step too much creates 3-29 extra iterations for
the next loop. this is still suboptimal since it always goes by 2^29
rather than using a smaller upscale factor when nearing the target,
but performance on common, small-magnitude, few-digit values has
already more than doubled with this change.
more optimizations on the way...
Diffstat (limited to 'src/internal')
| -rw-r--r-- | src/internal/floatscan.c | 54 |
1 files changed, 27 insertions, 27 deletions
diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c index 3aa54082..d5444daa 100644 --- a/src/internal/floatscan.c +++ b/src/internal/floatscan.c @@ -138,38 +138,12 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po e2 = 0; rp = lrp; - while (rp < 18+9*LD_B1B_DIG) { - uint32_t carry = 0; - e2 -= 29; - for (k=(z-1 & MASK); ; k=(k-1 & MASK)) { - uint64_t tmp = ((uint64_t)x[k] << 29) + carry; - if (tmp > 1000000000) { - carry = tmp / 1000000000; - x[k] = tmp % 1000000000; - } else { - carry = 0; - x[k] = tmp; - } - if (k==(z-1 & MASK) && k!=a && !x[k]) z = k; - if (k==a) break; - } - if (carry) { - rp += 9; - if (a == z) { - z = (z-1 & MASK); - x[z-1 & MASK] |= x[z]; - } - a = (a-1 & MASK); - x[a] = carry; - } - } - if (rp % 9) { static const int p10s[] = { 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10 }; - int rpm9 = rp % 9; + int rpm9 = rp>=0 ? rp%9 : rp%9+9; int p10 = p10s[rpm9-1]; uint32_t carry = 0; for (k=a; k!=z; k=(k+1 & MASK)) { @@ -190,6 +164,32 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po rp += 9-rpm9; } + while (rp < 9*LD_B1B_DIG || (rp == 9*LD_B1B_DIG && x[0]<th[0])) { + uint32_t carry = 0; + e2 -= 29; + for (k=(z-1 & MASK); ; k=(k-1 & MASK)) { + uint64_t tmp = ((uint64_t)x[k] << 29) + carry; + if (tmp > 1000000000) { + carry = tmp / 1000000000; + x[k] = tmp % 1000000000; + } else { + carry = 0; + x[k] = tmp; + } + if (k==(z-1 & MASK) && k!=a && !x[k]) z = k; + if (k==a) break; + } + if (carry) { + rp += 9; + if (a == z) { + z = (z-1 & MASK); + x[z-1 & MASK] |= x[z]; + } + a = (a-1 & MASK); + x[a] = carry; + } + } + for (;;) { uint32_t carry = 0; int sh = 1; |