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| author | Alan Modra <amodra@gmail.com> | 2017-09-09 21:55:22 +0930 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2017-09-10 01:55:16 +0930 |
| commit | 2420fff633eff03ec1f85eba82a926cd0ecf4229 (patch) | |
| tree | ce52c69c7236e211580be3aa4da6692022bbe0bc /ld/ld.texinfo | |
| parent | c5bce5c69721af8dae5c607e085e545cdba33ab1 (diff) | |
| download | gdb-2420fff633eff03ec1f85eba82a926cd0ecf4229.zip gdb-2420fff633eff03ec1f85eba82a926cd0ecf4229.tar.gz gdb-2420fff633eff03ec1f85eba82a926cd0ecf4229.tar.bz2 | |
PowerPC64 --plt-align
This changes the PowerPC64 --plt-align option to perform the usual
alignment of code as suggested by its name, as well as the previous
behaviour of padding so as to reduce boundary crossing. The old
behaviour is had by using a negative parameter.
The default is also changed to align plt stub code by default to 32
byte boundaries, the point being to get better bctr branch prediction
on power8 and power9 hardware.
bfd/
* elf64-ppp.c (plt_stub_pad): Handle positive and negative
plt_stub_align.
ld/
* ld.texinfo (--plt-align): Describe new behaviour of option.
* emultempl/ppc64elf.em (params): Default plt_stub_align to 5.
* testsuite/ld-powerpc/powerpc.exp: Pass --no-plt-align for
selected tests.
* testsuite/ld-powerpc/relbrlt.d: Pass --no-plt-align.
* testsuite/ld-powerpc/elfv2so.d: Adjust expected output.
Diffstat (limited to 'ld/ld.texinfo')
| -rw-r--r-- | ld/ld.texinfo | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/ld/ld.texinfo b/ld/ld.texinfo index ba19cd7..90a745a 100644 --- a/ld/ld.texinfo +++ b/ld/ld.texinfo @@ -7603,10 +7603,12 @@ off this feature. @item --plt-align @itemx --no-plt-align Use these options to control whether individual PLT call stubs are -padded so that they don't cross a 32-byte boundary, or to the -specified power of two boundary when using @code{--plt-align=}. Note -that this isn't alignment in the usual sense. By default PLT call -stubs are packed tightly. +aligned to a 32-byte boundary, or to the specified power of two +boundary when using @code{--plt-align=}. A negative value may be +specified to pad PLT call stubs so that they do not cross the +specified power of two boundary (or the minimum number of boundaries +if a PLT stub is so large that it must cross a boundary). By default +PLT call stubs are aligned to 32-byte boundaries. @cindex PowerPC64 PLT call stub static chain @kindex --plt-static-chain |