File 2002-erts-Refactor-and-cleanup-sys_double_to_chars_fast.patch of Package erlang
From b76d188778655394641f87ac0367fefecf233268 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Mon, 15 Jan 2018 19:13:25 +0100
Subject: [PATCH 3/3] erts: Refactor and cleanup sys_double_to_chars_fast
Replace long long with Uint64
---
erts/emulator/sys/common/erl_sys_common_misc.c | 106 ++++++++++++-------------
1 file changed, 49 insertions(+), 57 deletions(-)
diff --git a/erts/emulator/sys/common/erl_sys_common_misc.c b/erts/emulator/sys/common/erl_sys_common_misc.c
index ddb414580a..ba03a11405 100644
--- a/erts/emulator/sys/common/erl_sys_common_misc.c
+++ b/erts/emulator/sys/common/erl_sys_common_misc.c
@@ -158,59 +158,50 @@ int
sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
int compact)
{
- /* Note that some C compilers don't support "static const" propagation
- * so we use a defines */
#define SYS_DOUBLE_RND_CONST 0.5
#define FRAC_SIZE 52
#define EXP_SIZE 11
- #define EXP_MASK ((1ll << EXP_SIZE) - 1)
+ #define EXP_MASK (((Uint64)1 << EXP_SIZE) - 1)
#define MAX_DECIMALS (sizeof(cs_sys_double_pow10) \
/ sizeof(cs_sys_double_pow10[0]))
- #define FRAC_MASK ((1ll << FRAC_SIZE) - 1)
- #define FRAC_MASK2 ((1ll << (FRAC_SIZE + 1)) - 1)
- #define MAX_FLOAT (1ll << (FRAC_SIZE+1))
+ #define FRAC_MASK (((Uint64)1 << FRAC_SIZE) - 1)
+ #define FRAC_MASK2 (((Uint64)1 << (FRAC_SIZE + 1)) - 1)
+ #define MAX_FLOAT ((Uint64)1 << (FRAC_SIZE+1))
static const double cs_sys_double_pow10[] = {
- SYS_DOUBLE_RND_CONST / 1ll,
- SYS_DOUBLE_RND_CONST / 10ll,
- SYS_DOUBLE_RND_CONST / 100ll,
- SYS_DOUBLE_RND_CONST / 1000ll,
- SYS_DOUBLE_RND_CONST / 10000ll,
- SYS_DOUBLE_RND_CONST / 100000ll,
- SYS_DOUBLE_RND_CONST / 1000000ll,
- SYS_DOUBLE_RND_CONST / 10000000ll,
- SYS_DOUBLE_RND_CONST / 100000000ll,
- SYS_DOUBLE_RND_CONST / 1000000000ll,
- SYS_DOUBLE_RND_CONST / 10000000000ll,
- SYS_DOUBLE_RND_CONST / 100000000000ll,
- SYS_DOUBLE_RND_CONST / 1000000000000ll,
- SYS_DOUBLE_RND_CONST / 10000000000000ll,
- SYS_DOUBLE_RND_CONST / 100000000000000ll,
- SYS_DOUBLE_RND_CONST / 1000000000000000ll,
- SYS_DOUBLE_RND_CONST / 10000000000000000ll,
- SYS_DOUBLE_RND_CONST / 100000000000000000ll,
- SYS_DOUBLE_RND_CONST / 1000000000000000000ll
+ SYS_DOUBLE_RND_CONST / 1e0,
+ SYS_DOUBLE_RND_CONST / 1e1,
+ SYS_DOUBLE_RND_CONST / 1e2,
+ SYS_DOUBLE_RND_CONST / 1e3,
+ SYS_DOUBLE_RND_CONST / 1e4,
+ SYS_DOUBLE_RND_CONST / 1e5,
+ SYS_DOUBLE_RND_CONST / 1e6,
+ SYS_DOUBLE_RND_CONST / 1e7,
+ SYS_DOUBLE_RND_CONST / 1e8,
+ SYS_DOUBLE_RND_CONST / 1e9,
+ SYS_DOUBLE_RND_CONST / 1e10,
+ SYS_DOUBLE_RND_CONST / 1e11,
+ SYS_DOUBLE_RND_CONST / 1e12,
+ SYS_DOUBLE_RND_CONST / 1e13,
+ SYS_DOUBLE_RND_CONST / 1e14,
+ SYS_DOUBLE_RND_CONST / 1e15,
+ SYS_DOUBLE_RND_CONST / 1e16,
+ SYS_DOUBLE_RND_CONST / 1e17,
+ SYS_DOUBLE_RND_CONST / 1e18
};
- long long mantissa, int_part = 0, frac_part = 0;
- short exp;
+ Uint64 mantissa, int_part, frac_part;
+ int exp;
+ int fbits;
int max;
int neg;
double fr;
- union { long long L; double F; } x;
+ union { Uint64 L; double F; } x;
char *p = buffer;
if (decimals < 0)
return -1;
- /* Round the number to given decimal places. The number of 5's in the
- * SYS_DOUBLE_RND_CONST constant is chosen such that adding any more 5's doesn't
- * change the double precision of the number, i.e.:
- * 1> term_to_binary(0.55555555555555555, [{minor_version, 1}]).
- * <<131,70,63,225,199,28,113,199,28,114>>
- * 2> term_to_binary(0.5555555555555555555, [{minor_version, 1}]).
- * <<131,70,63,225,199,28,113,199,28,114>>
- */
if (f >= 0) {
neg = 0;
fr = decimals < MAX_DECIMALS ? (f + cs_sys_double_pow10[decimals]) : f;
@@ -241,7 +232,7 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
}
exp -= EXP_MASK >> 1;
- mantissa |= (1ll << FRAC_SIZE);
+ mantissa |= ((Uint64)1 << FRAC_SIZE);
/* Don't bother with optimizing too large numbers or too large precision */
if (x.F > MAX_FLOAT || decimals >= MAX_DECIMALS) {
@@ -256,14 +247,16 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
return p - buffer;
} else if (exp >= FRAC_SIZE) {
int_part = mantissa << (exp - FRAC_SIZE);
- exp = 0;
+ frac_part = 0;
+ fbits = FRAC_SIZE; /* not important as frac_part==0 */
} else if (exp >= 0) {
- int_part = mantissa >> (FRAC_SIZE - exp);
- frac_part = (mantissa << (exp + 1)) & FRAC_MASK2;
- exp = 0;
+ fbits = FRAC_SIZE - exp;
+ int_part = mantissa >> fbits;
+ frac_part = mantissa & (((Uint64)1 << fbits) -1);
} else /* if (exp < 0) */ {
+ int_part = 0;
frac_part = mantissa;
- exp = -(exp+1);
+ fbits = FRAC_SIZE - exp;
}
if (!int_part) {
@@ -273,9 +266,8 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
} else {
int ret, i, n;
while (int_part != 0) {
- long long j = int_part / 10;
- *p++ = (char)(int_part - ((j << 3) + (j << 1)) + '0');
- int_part = j;
+ *p++ = (char)((int_part % 10) + '0');
+ int_part /= 10;
}
if (neg)
*p++ = '-';
@@ -301,21 +293,21 @@ sys_double_to_chars_fast(double f, char *buffer, int buffer_size, int decimals,
max = decimals;
for (i = 0; i < max; i++) {
- if (frac_part > (ERTS_UINT64_MAX/16)) {
- frac_part /= 16;
- exp -= 4;
+ if (frac_part > (ERTS_UINT64_MAX/5)) {
+ frac_part >>= 3;
+ fbits -= 3;
}
- if (FRAC_SIZE + 1 + exp >= 64) {
+
+ /* Multiply by 10 (5*2) to extract decimal digit as integer part */
+ frac_part *= 5;
+ fbits--;
+
+ if (fbits >= 64) {
*p++ = '0';
- frac_part *= 5;
- exp--;
}
- else
- {
- frac_part *= 10;
-
- *p++ = (char)((frac_part >> (FRAC_SIZE + 1 + exp)) + '0');
- frac_part &= (1ll << (FRAC_SIZE + 1 + exp)) - 1;
+ else {
+ *p++ = (char)((frac_part >> fbits) + '0');
+ frac_part &= ((Uint64)1 << fbits) - 1;
}
}
--
2.16.0
