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Micro-optimize partial_die_info::read 

While profiling the DWARF reader, I noticed that
partial_die_info::read creates a vector to store attributes.  However,
the vector is not needed, as this code only processes a single
attribute at a time.

This patch removes the vector.  On my machine, this improves the time
of "./gdb ./gdb" from 2.22 seconds to 1.92 seconds (mean times over 10
runs).

Note that the attribute is initialized by read_attribute, so it does
not need any special initialization.  Avoiding this also improves
performance a bit.

Tested on x86-64 Fedora 30.  I'm checking this in.

gdb/ChangeLog
2020-04-02  Tom Tromey  <tromey@adacore.com>

	* dwarf2/read.c (partial_die_info::read): Do not create a vector
	of attributes.
This commit is contained in:
Tom Tromey 2020-04-02 12:49:35 -06:00
parent c90d28ac89
commit e7da7f8f71
2 changed files with 8 additions and 4 deletions
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5
gdb/ChangeLog
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@ -1,3 +1,8 @@
2020-04-02 Tom Tromey <tromey@adacore.com>
* dwarf2/read.c (partial_die_info::read): Do not create a vector
of attributes.
2020-04-02 Andrew Burgess <andrew.burgess@embecosm.com>
Bernd Edlinger <bernd.edlinger@hotmail.de>
Tom Tromey <tromey@adacore.com>

7
gdb/dwarf2/read.c
View File

@ -17879,18 +17879,17 @@ partial_die_info::read (const struct die_reader_specs *reader,
int has_high_pc_attr = 0;
int high_pc_relative = 0;
std::vector<struct attribute> attr_vec (abbrev.num_attrs);
for (i = 0; i < abbrev.num_attrs; ++i)
{
attribute attr;
bool need_reprocess;
info_ptr = read_attribute (reader, &attr_vec[i], &abbrev.attrs[i],
info_ptr = read_attribute (reader, &attr, &abbrev.attrs[i],
info_ptr, &need_reprocess);
/* String and address offsets that need to do the reprocessing have
already been read at this point, so there is no need to wait until
the loop terminates to do the reprocessing. */
if (need_reprocess)
read_attribute_reprocess (reader, &attr_vec[i]);
attribute &attr = attr_vec[i];
read_attribute_reprocess (reader, &attr);
/* Store the data if it is of an attribute we want to keep in a
partial symbol table. */
switch (attr.name)