The Maj macro is used where multiple things are added
together, so making Maj a sum of two expressions allows
some extra freedom for the compiler to schedule the
instructions.
I learned this trick from
<http://www.hackersdelight.org/corres.txt>.
This looks weird because the rotations become sequential,
but it helps quite a bit on both 32-bit and 64-bit x86:
- It requires fewer instructions on two-operand
instruction sets like x86.
- It requires one register less which matters especially
on 32-bit x86.
I hope this doesn't hurt other archs.
I didn't invent this idea myself, but I don't remember where
I saw it first.
This way a branch isn't needed for each operation
to choose between blk0 and blk2, and still the code
doesn't grow as much as it would with full unrolling.
This commit just adds the function. Its uses will be in
separate commits.
This hasn't been tested much yet and it's perhaps a bit early
to commit it but if there are bugs they should get found quite
quickly.
Thanks to Jun I Jin from Intel for help and for pointing out
that string comparison needs to be optimized in liblzma.
Mimic the original grep behavior and return exit_success when
at least one xz compressed file matches given pattern.
Original bugreport:
https://bugzilla.redhat.com/show_bug.cgi?id=1108085
Thanks to Pavel Raiskup for the patch.
This avoids a memzero() call for a newly-allocated memory,
which can be expensive when encoding small streams with
an over-sized dictionary.
To avoid using lzma_alloc_zero() for memory that doesn't
need to be zeroed, lzma_mf.son is now allocated separately,
which requires handling it separately in normalize() too.
Thanks to Vincenzo Innocente for reporting the problem.
In this case "make install" could fail if the man page directory
didn't already exist at the destination. If it did exist, a
dangling symlink was created there. Now the link is omitted
instead. This isn't the best fix but it's better than the old
behavior.
Add a note about failing "make check". The source of
the problem should be fixed in libtool (if it really is
a libtool bug and not mine) but I'm unable to spend time
on that for now. Thanks to Nelson H. F. Beebe for reporting
the issue.
Add a note about a possible need to run "ldconfig" after
"make install".
I don't know the details but I have an impression that there's
no problem in practice if using GCC since people have built xz
with GCC (without patching xz), but renaming the variable cannot
hurt either.
Thanks to Mark Ashley.
Previously, --block-list and --block-size only worked together
in threaded mode. Boundaries are specified by --block-list, but
--block-size specifies the maximum size for a Block. Now this
works in single-threaded mode too.
Thanks to James M Leddy for the original patch.
Lasse Collin