Re: [PATCH 1/6] rtl-ssa: Ensure global registers are live on exit

[Jeff Law <jeffreyalaw@gmail.com>]

On 10/24/23 04:50, Richard Sandiford wrote:
> RTL-SSA mostly relies on DF for block-level register liveness
> information, including artificial uses and defs at the beginning
> and end of blocks.  But one case was missing.  DF does not add
> artificial uses of global registers to the beginning or end
> of a block.  Instead it marks them as used within every block
> when computing LR and LIVE problems.
> 
> For RTL-SSA, global registers behave like memory, which in
> turn behaves like gimple vops.  We need to ensure that they
> are live on exit so that final definitions do not appear
> to be unused.
> 
> Also, the previous live-on-exit handling only considered the exit
> block itself.  It needs to consider non-local gotos as well, since
> they jump directly to some code in a parent function and so do
> not have a path to the exit block.
> 
> gcc/
> 	* rtl-ssa/blocks.cc (function_info::add_artificial_accesses): Force
> 	global registers to be live on exit.  Handle any block with zero
> 	successors like an exit block.
OK
jeff