[PATCH 0/3] RISC-V: memcpy(): align dest when misaligned access is

[ma.mandourr@gmail.com]

From: Mahmoud Abumandour <ma.mandourr@gmail.com>

Add a code path for when source and dest are differently aligned.

If misaligned access is slow or prohibited (i.e. `__riscv_misaligned_slow` or
`__riscv_misaligned_avoid` is defined), and the alignments of the source and destination are
different, we align the destination to do XLEN stores. This uses only one
aligned store for every four (or eight for XLEN == 64) bytes of data.

This only affects the case where source and destination are differently aligned.
Previously, this case was handled by copying one byte at a time. The new
approach significantly reduces the number of executed (dynamic) instructions
(30% weighted average for `-mstrict-align`, while not affecting
`-mno-strict-align`, which is expected).

A comparison between the implementations with raw numbers is posted here:
    https://docs.google.com/spreadsheets/d/1KDnfhYVFQYIXb23LjsgWFyWna4A_9mcRZRLm_u0zELE/edit?usp=sharing

While at it, the function is generally improved to use `uintxlen_t` and
eliminate gotos and macros.

Mahmoud Abumandour (3):
  RISC-V: memcpy() Use uintxlen_t for xlen-sized copy
  RISC-V: memcpy() Use inline functions instead of macros and gotos
  RISC-V: memcpy() align dest when misaligned access is prohibited

 newlib/libc/machine/riscv/memcpy.c | 163 +++++++++++++++++++----------
 1 file changed, 109 insertions(+), 54 deletions(-)

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2.43.0