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re PR libfortran/38199 (missed optimization: I/O performance)

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2014-03-08  Jerry DeLisle  <jvdelisle@gcc.gnu>

	PR libfortran/38199
	* io/list_read.c (next_char): Delete unuseful error checks.
	(eat_spaces): For character array reading, skip ahead over
	spaces rather than call next_char multiple times.

From-SVN: r208438
This commit is contained in:
Jerry DeLisle 2014-03-09 03:17:16 +00:00
parent a5165cff4d
commit c8869272f7
2 changed files with 53 additions and 4 deletions
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7
libgfortran/ChangeLog
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@ -1,3 +1,10 @@
2014-03-08 Jerry DeLisle <jvdelisle@gcc.gnu>
PR libfortran/38199
* io/list_read.c (next_char): Delete unuseful error checks.
(eat_spaces): For character array reading, skip ahead over
spaces rather than call next_char multiple times.
2014-03-08 Tobias Burnus <burnus@net-b.de>
* libgfortran.h (unlikely, likely): Add usage comment.

50
libgfortran/io/list_read.c
View File

@ -160,7 +160,7 @@ next_char (st_parameter_dt *dtp)
dtp->u.p.line_buffer_pos = 0;
dtp->u.p.line_buffer_enabled = 0;
}
}
/* Handle the end-of-record and end-of-file conditions for
internal array unit. */
@ -208,16 +208,16 @@ next_char (st_parameter_dt *dtp)
c = cc;
}
if (length < 0)
if (unlikely (length < 0))
{
generate_error (&dtp->common, LIBERROR_OS, NULL);
return '\0';
}
if (is_array_io (dtp))
{
/* Check whether we hit EOF. */
if (length == 0)
if (unlikely (length == 0))
{
generate_error (&dtp->common, LIBERROR_INTERNAL_UNIT, NULL);
return '\0';
@ -264,6 +264,48 @@ eat_spaces (st_parameter_dt *dtp)
{
int c;
/* If internal character array IO, peak ahead and seek past spaces.
This is an optimazation to eliminate numerous calls to
next character unique to character arrays with large character
lengths (PR38199). */
if (is_array_io (dtp))
{
gfc_offset offset = stell (dtp->u.p.current_unit->s);
gfc_offset limit = dtp->u.p.current_unit->bytes_left;
if (dtp->common.unit) /* kind=4 */
{
gfc_char4_t cc;
limit *= (sizeof (gfc_char4_t));
do
{
cc = dtp->internal_unit[offset];
offset += (sizeof (gfc_char4_t));
dtp->u.p.current_unit->bytes_left--;
}
while (offset < limit && (cc == (gfc_char4_t)' '
|| cc == (gfc_char4_t)'\t'));
/* Back up, seek ahead, and fall through to complete the
process so that END conditions are handled correctly. */
dtp->u.p.current_unit->bytes_left++;
sseek (dtp->u.p.current_unit->s,
offset-(sizeof (gfc_char4_t)), SEEK_SET);
}
else
{
do
{
c = dtp->internal_unit[offset++];
dtp->u.p.current_unit->bytes_left--;
}
while (offset < limit && (c == ' ' || c == '\t'));
/* Back up, seek ahead, and fall through to complete the
process so that END conditions are handled correctly. */
dtp->u.p.current_unit->bytes_left++;
sseek (dtp->u.p.current_unit->s, offset-1, SEEK_SET);
}
}
/* Now skip spaces, EOF and EOL are handled in next_char. */
do
c = next_char (dtp);
while (c != EOF && (c == ' ' || c == '\t'));