CIRCLE WITH A DOT

@zwarich @pervognsen risc-v will do things like rewrite registers in instructions, delete instructions, rewrite them with a smaller variant, etc etc etc. Now remember that alignment needs to be preserved and enjoy your headache.

@zwarich @pervognsen nop-ing is fine compared to relaxation. AArch64 doesn't have variable-width instructions, and doesn't delete instructions during relaxation (shuffling everything afterwards)

@pervognsen I don't have data to back this up but I presume this exact inline asm string in the x86 callback was in a core header/library somewhere, called from a hot loop, and this made a specific benchmark faster on a machine that had a better core than the header presumed.

@zwarich @pervognsen let me introduce you to RISC-V Linker Relaxations, which both inspect and modify machine code bytes to change the sequence to better ones (they still use relocations)

@pervognsen Nothing was sacred. It's now more sacred than it was. Though I think AMDGPU? wants to read (but not modify) the string for scheduling hints/annotations.

@regehr oh sure, it probably also causes fewer heart attacks.

@regehr yours probably doesn't have 10s of years of griddle char to properly season everything fried.