Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit6b423ec

Browse files
committed
Improve performance of pg_strtointNN functions
Experiments have shown that modern versions of both gcc and clang areunable to fully optimize the multiplication by 10 that we're doing in thepg_strtointNN functions. Both compilers seem to be making use of "imul",which is not the most efficient way to multiply by 10. This seems to bedue to the overflow checking that we're doing. Without the overflowchecks, both those compilers switch to a more efficient method ofmultiplying by 10. In absence of overflow concern, integer multiplicationby 10 can be done by bit-shifting left 3 places to multiply by 8 and thenadding the original value twice.To allow compilers this flexibility, here we adjust the code so that weaccumulate the number as an unsigned version of the type and remove theuse of pg_mul_sNN_overflow() and pg_sub_sNN_overflow(). The overflowchecking can be done simply by checking if the accumulated value has gonebeyond a 10th of the maximum *signed* value for the given type. If it hasthen the accumulation of the next digit will cause an overflow. Afterthis is done, we do a final overflow check before converting the unsignedversion of the number back to its signed counterpart.Testing has shown about an 8% speedup of a COPY into a table containing 2INT columns.Author: David Rowley, Dean RasheedDiscussion:https://postgr.es/m/CAApHDvrL6_+wKgPqRHr7gH_6xy3hXM6a3QCsZ5ForurjDFfenA@mail.gmail.comDiscussion:https://postgr.es/m/CAApHDvrdYByjfj-=WbmVNFgmVZg88-dE7heukw8p55aJ+W=qxQ@mail.gmail.com
1 parent29452de commit6b423ec

File tree

1 file changed

+42
-44
lines changed

1 file changed

+42
-44
lines changed

‎src/backend/utils/adt/numutils.c

Lines changed: 42 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -91,15 +91,15 @@ decimalLength64(const uint64 v)
9191
* Allows any number of leading or trailing whitespace characters. Will throw
9292
* ereport() upon bad input format or overflow.
9393
*
94-
* NB: Accumulate input asa negative number, to deal with two's complement
94+
* NB: Accumulate input asan unsigned number, to deal with two's complement
9595
* representation of the most negative number, which can't be represented as a
96-
* positive number.
96+
*signedpositive number.
9797
*/
9898
int16
9999
pg_strtoint16(constchar*s)
100100
{
101101
constchar*ptr=s;
102-
int16tmp=0;
102+
uint16tmp=0;
103103
boolneg= false;
104104

105105
/* skip leading spaces */
@@ -122,11 +122,10 @@ pg_strtoint16(const char *s)
122122
/* process digits */
123123
while (*ptr&&isdigit((unsignedchar)*ptr))
124124
{
125-
int8digit= (*ptr++-'0');
126-
127-
if (unlikely(pg_mul_s16_overflow(tmp,10,&tmp))||
128-
unlikely(pg_sub_s16_overflow(tmp,digit,&tmp)))
125+
if (unlikely(tmp> (PG_INT16_MAX /10)))
129126
gotoout_of_range;
127+
128+
tmp=tmp*10+ (*ptr++-'0');
130129
}
131130

132131
/* allow trailing whitespace, but not other trailing chars */
@@ -136,15 +135,18 @@ pg_strtoint16(const char *s)
136135
if (unlikely(*ptr!='\0'))
137136
gotoinvalid_syntax;
138137

139-
if (!neg)
138+
if (neg)
140139
{
141-
/*could fail if input is most negative number */
142-
if (unlikely(tmp==PG_INT16_MIN))
140+
/*check the negative equivalent will fit without overflowing */
141+
if (tmp> (uint16) (-(PG_INT16_MIN+1))+1)
143142
gotoout_of_range;
144-
tmp=-tmp;
143+
return-((int16)tmp);
145144
}
146145

147-
returntmp;
146+
if (tmp>PG_INT16_MAX)
147+
gotoout_of_range;
148+
149+
return (int16)tmp;
148150

149151
out_of_range:
150152
ereport(ERROR,
@@ -167,15 +169,15 @@ pg_strtoint16(const char *s)
167169
* Allows any number of leading or trailing whitespace characters. Will throw
168170
* ereport() upon bad input format or overflow.
169171
*
170-
* NB: Accumulate input asa negative number, to deal with two's complement
172+
* NB: Accumulate input asan unsigned number, to deal with two's complement
171173
* representation of the most negative number, which can't be represented as a
172-
* positive number.
174+
*signedpositive number.
173175
*/
174176
int32
175177
pg_strtoint32(constchar*s)
176178
{
177179
constchar*ptr=s;
178-
int32tmp=0;
180+
uint32tmp=0;
179181
boolneg= false;
180182

181183
/* skip leading spaces */
@@ -198,11 +200,10 @@ pg_strtoint32(const char *s)
198200
/* process digits */
199201
while (*ptr&&isdigit((unsignedchar)*ptr))
200202
{
201-
int8digit= (*ptr++-'0');
202-
203-
if (unlikely(pg_mul_s32_overflow(tmp,10,&tmp))||
204-
unlikely(pg_sub_s32_overflow(tmp,digit,&tmp)))
203+
if (unlikely(tmp> (PG_INT32_MAX /10)))
205204
gotoout_of_range;
205+
206+
tmp=tmp*10+ (*ptr++-'0');
206207
}
207208

208209
/* allow trailing whitespace, but not other trailing chars */
@@ -212,15 +213,18 @@ pg_strtoint32(const char *s)
212213
if (unlikely(*ptr!='\0'))
213214
gotoinvalid_syntax;
214215

215-
if (!neg)
216+
if (neg)
216217
{
217-
/*could fail if input is most negative number */
218-
if (unlikely(tmp==PG_INT32_MIN))
218+
/*check the negative equivalent will fit without overflowing */
219+
if (tmp> (uint32) (-(PG_INT32_MIN+1))+1)
219220
gotoout_of_range;
220-
tmp=-tmp;
221+
return-((int32)tmp);
221222
}
222223

223-
returntmp;
224+
if (tmp>PG_INT32_MAX)
225+
gotoout_of_range;
226+
227+
return (int32)tmp;
224228

225229
out_of_range:
226230
ereport(ERROR,
@@ -243,25 +247,17 @@ pg_strtoint32(const char *s)
243247
* Allows any number of leading or trailing whitespace characters. Will throw
244248
* ereport() upon bad input format or overflow.
245249
*
246-
* NB: Accumulate input asa negative number, to deal with two's complement
250+
* NB: Accumulate input asan unsigned number, to deal with two's complement
247251
* representation of the most negative number, which can't be represented as a
248-
* positive number.
252+
*signedpositive number.
249253
*/
250254
int64
251255
pg_strtoint64(constchar*s)
252256
{
253257
constchar*ptr=s;
254-
int64tmp=0;
258+
uint64tmp=0;
255259
boolneg= false;
256260

257-
/*
258-
* Do our own scan, rather than relying on sscanf which might be broken
259-
* for long long.
260-
*
261-
* As INT64_MIN can't be stored as a positive 64 bit integer, accumulate
262-
* value as a negative number.
263-
*/
264-
265261
/* skip leading spaces */
266262
while (*ptr&&isspace((unsignedchar)*ptr))
267263
ptr++;
@@ -282,11 +278,10 @@ pg_strtoint64(const char *s)
282278
/* process digits */
283279
while (*ptr&&isdigit((unsignedchar)*ptr))
284280
{
285-
int8digit= (*ptr++-'0');
286-
287-
if (unlikely(pg_mul_s64_overflow(tmp,10,&tmp))||
288-
unlikely(pg_sub_s64_overflow(tmp,digit,&tmp)))
281+
if (unlikely(tmp> (PG_INT64_MAX /10)))
289282
gotoout_of_range;
283+
284+
tmp=tmp*10+ (*ptr++-'0');
290285
}
291286

292287
/* allow trailing whitespace, but not other trailing chars */
@@ -296,15 +291,18 @@ pg_strtoint64(const char *s)
296291
if (unlikely(*ptr!='\0'))
297292
gotoinvalid_syntax;
298293

299-
if (!neg)
294+
if (neg)
300295
{
301-
/*could fail if input is most negative number */
302-
if (unlikely(tmp==PG_INT64_MIN))
296+
/*check the negative equivalent will fit without overflowing */
297+
if (tmp> (uint64) (-(PG_INT64_MIN+1))+1)
303298
gotoout_of_range;
304-
tmp=-tmp;
299+
return-((int64)tmp);
305300
}
306301

307-
returntmp;
302+
if (tmp>PG_INT64_MAX)
303+
gotoout_of_range;
304+
305+
return (int64)tmp;
308306

309307
out_of_range:
310308
ereport(ERROR,

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp