AAPCS64 reserves any of X9-X15 for a compiler to choose to use for this
purpose, and says not to use X16 or X18 like GCC (and the previous
implementation) chose to use. The X18 register may need to get used by
the kernel in some circumstances, as specified by the platform ABI, so
it is generally an unwise choice. Simply choosing a different register
fixes the problem of this being broken on any platform that actually
follows the platform ABI (which is all of them except EABI, if I am
reading this linux kernel bug correctly
https://lkml2.uits.iu.edu/hypermail/linux/kernel/2001.2/01502.html). As
a side benefit, also generate slightly better code and avoids needing
the compiler-rt to be present. I did that by following the XCore
implementation instead of PPC (although in hindsight, following the
RISCV might have been slightly more readable). That X18 is wrong to use
for this purpose has been known for many years (e.g.
https://www.mail-archive.com/gcc@gcc.gnu.org/msg76934.html) and also
known that fixing this to use one of the correct registers is not an ABI
break, since this only appears inside of a translation unit. Some of the
other temporary registers (e.g. X9) are already reserved inside llvm for
internal use as a generic temporary register in the prologue before
saving registers, while X15 was already used in rare cases as a scratch
register in the prologue as well, so I felt that seemed the most logical
choice to choose here.
The lowercase __ppc__ is not defined by Linux GCC, therefore it lures
users to write code which is not portable to GCC. Migrate to __powerpc__ in
preparation for undefining __ppc__. __powerpc__ is much more common than
__PPC__.
Use the uniform single line C++/99 style for code comments.
This is part of the cleanup proposed in "[RFC] compiler-rt builtins
cleanup and refactoring".
Differential Revision: https://reviews.llvm.org/D60352
llvm-svn: 359411
Update formatting to use the LLVM style.
This is part of the cleanup proposed in "[RFC] compiler-rt builtins
cleanup and refactoring".
Differential Revision: https://reviews.llvm.org/D60351
llvm-svn: 359410
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351648
