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Re: PowerPC 'future' patches introduction
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Michael Meissner <meissner at linux dot ibm dot com>, gcc-patches at gcc dot gnu dot org, dje dot gcc at gmail dot com, Alan Modra <amodra at gmail dot com>
- Date: Wed, 14 Aug 2019 19:02:15 -0500
- Subject: Re: PowerPC 'future' patches introduction
- References: <20190814205732.GA11956@ibm-toto.the-meissners.org>
Hi Mike,
On Wed, Aug 14, 2019 at 04:57:32PM -0400, Michael Meissner wrote:
> to the current location instead of a base register, giving pc-relative
> addressing. Pc-relative addressing will be supported in the next ABI (3.1) as
> an alternative to the current TOC based addressing.
That's not an ABI version, that's an ISA version. But it will be in a
future ELFv2 ABI version, yes.
> The fifth patch switches the default when you use -mcpu=future to use
> pc-relative instructions instead of using the TOC by default.
As David reminded me, you should only do this on OSes where this works.
Only for ABIs that support PCREL, even? Or both.
> The seventh patch adds a new RTL pass to implement the PCREL_OPT relocations
> that will be part of the ISA 3.1 specification.
Some version of the ELFv2 ABI again?
Segher