SPARC and MIPS CPUs don't have special instructions to count
leading/trailing zeroes. The compiler-rt library provides fallback
rountines for these. The 64-bit routines, __clzdi2 and __ctzdi2, are
implemented as simple wrappers around the compiler built-in
__builtin_clz(), assuming these will expand to either 32-bit
CPU instructions or calls to __clzsi2 and __ctzsi2.
Unfortunately, our GCC 4.2 probably thinks that because the operand is
stored in a 64-bit register, it might just be a better idea to invoke
its 64-bit equivalent, simply resulting into endless recursion. Fix this
by defining __builtin_clz and __builtin_ctz to __clzsi2 and __ctzsi2
explicitly.
This version of libcompiler_rt adds support for __mulo[sdt]i4(), which
computes a multiply and its overflow flag. There are also a lot of
cleanup fixes to headers that don't really affect us.
Updating to this revision should make it a bit easier to contribute
changes back to the LLVM developers.
It seems there have only been a small amount to the compiler-rt source
code in the mean time. I'd rather have the code in sync as much as
possible by the time we release 9.0. Changes:
- The libcompiler_rt library is now dual licensed under both the
University of Illinois "BSD-Like" license and the MIT license.
- Our local modifications for using .hidden instead of .private_extern
have been upstreamed, meaning our changes to lib/assembly.h can now be
reverted.
- A possible endless recursion in __modsi3() has been fixed.
- Support for ARM EABI has been added, but it has no effect on FreeBSD
(yet).
- The functions __udivmodsi4 and __divmodsi4 have been added.
Requested by: many, including bf@ and Pedro Giffuni
