[PATCH 1/2] Add new RTX instruction class FILLER_INSN
Wed Aug 19 17:28:21 GMT 2020
On Wed, Aug 19, 2020 at 11:13:40AM +0200, Andrea Corallo wrote:
> Segher Boessenkool <firstname.lastname@example.org> writes:
> > So I wonder if this cannot be done with some kind of NOTE, instead?
> I was having a look into reworking this using an insn note as (IIUC)
> suggested. The idea is appealing but looking into insn-notes.def I've
> found the following comment:
> "We are slowly removing the concept of insn-chain notes from the
> compiler. Adding new codes to this file is STRONGLY DISCOURAGED.
> If you think you need one, look for other ways to express what you
> mean, such as register notes or bits in the basic-block structure."
That is from 2004. Since then 9 note types have been removed, but 7
new types added. (There are 18 insn note types now).
> Would still be justificated in this case to proceed this way?
Yes, it is a lesser evil imho.
> The other
> option would be to add the information into the basic-block or into
> struct rtx_jump_insn.
Or just look at the insn code, define a "filler-nop" insn, allow those
after BBs? Any reason that wouldn't work?
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