Darwin: add x86_64h slice for Haswell.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@199996 91177308-0d34-0410-b5e6-96231b3b80d8
Implement __ARM_ARCH if the compiler lacks it. Add feature tests for bx and clz.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@199998 91177308-0d34-0410-b5e6-96231b3b80d8
Provide support for ARMv4, lacking bx and clz. Unroll the
test-and-subtract loop and compute the initial block as address,
shaving off between 5% and 10% on Cortex A9 and 30%+ a Raspberry Pi.
Code written by Matt Thomas and Joerg Sonnenberger.

Differential Revision: http://llvm-reviews.chandlerc.com/D2595


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200001 91177308-0d34-0410-b5e6-96231b3b80d8