[PATCH 3/5] regrename: Don't rename restores
Jeff Law
law@redhat.com
Mon Sep 26 16:44:00 GMT 2016
On 09/23/2016 02:21 AM, Segher Boessenkool wrote:
> A restore is supposed to restore some certain register. Restoring it
> into some other register will not work. Don't.
>
>
> 2016-09-23 Segher Boessenkool <segher@kernel.crashing.org>
>
> * regrename.c (build_def_use): Invalidate chains that have a
> REG_CFA_RESTORE on some instruction.
>
> ---
> gcc/regrename.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/gcc/regrename.c b/gcc/regrename.c
> index 54c7768..00a5d02 100644
> --- a/gcc/regrename.c
> +++ b/gcc/regrename.c
> @@ -1867,6 +1867,12 @@ build_def_use (basic_block bb)
> scan_rtx (insn, &XEXP (note, 0), NO_REGS, terminate_dead,
> OP_IN);
> }
> +
> + /* Step 8: Kill the chains involving register restores. Those
> + should restore _that_ register. */
> + for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
> + if (REG_NOTE_KIND (note) == REG_CFA_RESTORE)
> + scan_rtx (insn, &XEXP (note, 0), NO_REGS, mark_all_read, OP_IN);
> }
> else if (DEBUG_INSN_P (insn)
> && !VAR_LOC_UNKNOWN_P (INSN_VAR_LOCATION_LOC (insn)))
Seems like a good thing regardless of the shrink-wrapping changes.
There's a comment about 200 lines earlier (egad) which outlines the
steps. Can you please add a comment there too.
It would probably be a good idea to refactor build_def_use a bit, but
I'd understand if you don't want to tackle that. I don't think that
desire should block this patch.
As I've said before, I'm not sure we're getting CFA notes right,
particularly on the older ports, but I don't think that should block
this patch.
With the earlier comment update change this is OK.
jeff
More information about the Gcc-patches
mailing list