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[bfd] Provide 8-byte minimum alignment for .plt section

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This change increases the default alignment for the .plt section
	from 4 bytes to 8 bytes.  When function descriptors are 8-byte
	aligned, they can be updated atomically on 32-bit hppa.  This
	helps with ordering issues on SMP machines.  It also ensures
	that descriptors reside on the same cache line.  This reduces
	the probability of a double TLB miss in a call.

	2019-10-20  John David Anglin  <danglin@gcc.gnu.org>

		* elf32-hppa.c (elf32_hppa_size_dynamic_sections): Provide 8-byte
		minimum alignment for .plt section.
This commit is contained in:
John David Anglin 2019-10-20 12:01:58 -04:00
parent 80051c7439
commit 2c9e9550ca
2 changed files with 8 additions and 2 deletions
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5
bfd/ChangeLog
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@ -1,3 +1,8 @@
2019-10-20 John David Anglin <danglin@gcc.gnu.org>
* elf32-hppa.c (elf32_hppa_size_dynamic_sections): Provide 8-byte
minimum alignment for .plt section.
2019-10-19 John David Anglin <danglin@gcc.gnu.org>
* elf32-hppa.c: Revise import stub sequences.

5
bfd/elf32-hppa.c
View File

@ -2280,10 +2280,11 @@ elf32_hppa_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
against the .got section. */
int gotalign = bfd_section_alignment (htab->etab.sgot);
int pltalign = bfd_section_alignment (sec);
int align = gotalign > 3 ? gotalign : 3;
bfd_size_type mask;
if (gotalign > pltalign)
bfd_set_section_alignment (sec, gotalign);
if (align > pltalign)
bfd_set_section_alignment (sec, align);
mask = ((bfd_size_type) 1 << gotalign) - 1;
sec->size = (sec->size + sizeof (plt_stub) + mask) & ~mask;
}