On Wed, Feb 21, 2024 at 10:03:17AM +0000, Richard Sandiford wrote:
> In this PR, the SME mode-switching code needs to insert a stack-probe
> loop for an alloca. This patch allows the target to do that.
>
> There are two parts to it: allowing loops for insertions in blocks,
> and allowing them for insertions on edges. The former can be handled
> entirely within mode-switching itself, by recording which blocks have
> had new branches inserted. The latter requires an extension to
> commit_one_edge_insertion.
>
> I think the extension to commit_one_edge_insertion makes logical sense,
> since it already explicitly allows internal loops during RTL expansion.
> The single-block find_sub_basic_blocks is a relatively recent addition,
> so wouldn't have been available when the code was originally written.
>
> The patch also has a small and obvious fix to make the aarch64 emit
> hook cope with labels.
>
> I've added specific -fstack-clash-protection versions of all
> aarch64-sme.exp tests that previously failed because of this bug.
> I've also added -fno-stack-clash-protection to the original versions
> of these tests if they contain scans that assume no protection.
>
> Tested on aarch64-linux-gnu. OK to install?
>
> Richard
>
>
> gcc/
> PR target/113220
> * cfgrtl.cc (commit_one_edge_insertion): Handle sequences that
> contain jumps even if called after initial RTL expansion.
> * mode-switching.cc: Include cfgbuild.h.
> (optimize_mode_switching): Allow the sequence returned by the
> emit hook to contain internal jumps. Record which blocks
> contain such jumps and split the blocks at the end.
> * config/aarch64/aarch64.cc (aarch64_mode_emit): Check for
> non-debug insns when scanning the sequence.
LGTM.
Jakub
