On 3/19/24 2:05 PM, Vineet Gupta wrote:
Just to be clear, the changes don't misalign the stack pointer at all.
They merely have the potential to create *another* pointer into the
stack which may or may not be aligned. Which is totally normal, it's no
different than taking the address of a char on the stack.
Right I never saw any sp,sp,2047 getting generated - not even in the
first version of patch which lacked any filtering of stack regs via
riscv_reg_frame_related () and obviously didn't have the stack variant
of splitter. I don't know if that is just being lucky and not enough
testing exposure (I only spot checked buildroot libc, vmlinux) or
something somewhere enforces that.
However given that misaligned pointer off of stack is a non-issue, I
think we can do the following:
1. keep just one splitter with 2047 based predicates and constraint (and
not 2032) for both stack-related and general regs.
2. gate the splitter on only operands[0] being not stack related
(currently it checks for either [0] or [1]) - this allows the prominent
case where SP is simply a src, and avoids when any potential shenanigans
to SP itself.
Works for me.
Jeff
