Update documentation

1 files changed, 20 insertions, 1 deletions

diff --git a/ppc_simd.h b/ppc_simd.h
index 47ffcfde..8c43cc81 100644
--- a/ppc_simd.h
+++ b/ppc_simd.h
@@ -8,7 +8,7 @@
 /// \details The abstractions are necesssary to support back to GCC 4.8 and

 ///  XLC 11 and 12. GCC 4.8 and 4.9 are still popular, and they are the

 ///  default compiler for GCC112, GCC119 and others on the compile farm.

-///  Older IBM XL C/C++ compilers also experience it due to lack of

+///  Older IBM XL C/C++ compilers also have the need due to lack of

 ///  <tt>vec_xl</tt> and <tt>vec_xst</tt> support on some platforms. Modern

 ///  compilers provide best support and don't need many of the hacks

 ///  below.

@@ -44,6 +44,25 @@
 ///  renamed to <tt>Vec{FuncName}</tt>. For example, <tt>VectorAnd</tt> was

 ///  changed to <tt>VecAnd</tt>. The name change helped consolidate two

 ///  slightly different implementations.

+/// \details At Crypto++ 8.3 the library added select 64-bit functions for

+///  32-bit Altivec. For example, <tt>VecAdd64</tt> and <tt>VecSub64</tt>

+///  take 32-bit vectors and adds or subtracts them as if there were vectors

+///  with two 64-bit elements. The functions dramtically improve performance

+///  for some algorithms on some platforms, like SIMON128 and SPECK128 on

+///  Power6 and earlier. For example, SPECK128 improved from 70 cpb to

+///  10 cpb on an old PowerMac. Use the functions like shown below.

+///  <pre>

+///    \#if defined(_ARCH_PWR8)

+///    \#  define speck128_t uint64x2_p

+///    \#else

+///    \#  define speck128_t uint32x4_p

+///    \#endif

+///

+///    speck128_t rk, x1, x2, y1, y2;

+///    rk = (speck128_t)VecLoadAligned(ptr);

+///    x1 = VecRotateRight64<8>(x1);

+///    x1 = VecAdd64(x1, y1);

+///    ...</pre>

 /// \since Crypto++ 6.0, LLVM Clang compiler support since Crypto++ 8.0

 

 // Use __ALTIVEC__, _ARCH_PWR7, __VSX__, and _ARCH_PWR8 when detecting