This allows debuggers and profilers to reliably capture backtraces from
within the x86-64 SIMD functions.
In places where rbp was previously used to access temporary variables
(after stack alignment), we now use r15 and save/restore it accordingly.
The total amount of work is approximately the same, because the previous
code pushed the pre-alignment stack pointer to the aligned stack. The
new prologue and epilogue actually have fewer instructions.
Also note that the {un}collect_args macros now use rbp instead of rax to
access arguments passed on the stack, so we save a few instructions
there as well.
Based on:
debcc7c3b4Closes#707Closes#708
7b844bfda6