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Re: [PATCH 5/5] rs6000: Do not allow TImode with -m32 -mpowerpc64
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: David Edelsohn <dje dot gcc at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 16 Jan 2015 10:55:43 -0600
- Subject: Re: [PATCH 5/5] rs6000: Do not allow TImode with -m32 -mpowerpc64
- Authentication-results: sourceware.org; auth=none
- References: <a0366c6b956020e6762b6b78a73b20aba5ec1408 dot 1421282067 dot git dot segher at kernel dot crashing dot org> <687b2e40d388708e5b7604b1fcc1ce7e4b127b5b dot 1421282067 dot git dot segher at kernel dot crashing dot org> <CAGWvnyn2ksx+cdH4kTBc0w8Bd+ty0hMiJSP=6vM_EvkyMY1D1Q at mail dot gmail dot com>
On Thu, Jan 15, 2015 at 11:06:38AM -0500, David Edelsohn wrote:
> On Wed, Jan 14, 2015 at 8:14 PM, Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> > This fixes 141 FAILs.
> >
> > -mpowerpc64 does not change the ABI, but default_scalar_mode_supported_p
> > does not know that, and allows TImode for -m32 -mpowerpc64.
> Would you please add a comment that efficient TImode arithmetic
> requires carry to explain the TARGET_32BIT relationship?
I expanded the comment to:
/* -m32 does not support TImode. This is the default, from
default_scalar_mode_supported_p. For -m32 -mpowerpc64 we want the
same ABI as for -m32. But default_scalar_mode_supported_p allows
integer modes of precision 2 * BITS_PER_WORD, which matches TImode
for -mpowerpc64. */
because the reasons why we do or do not suppoort TImode with -m32 are
pretty much irrelevant here. Hope that's okay.
> We can think about providing TImode logical operations in 32 bit, in
> the long run.
Generic code would handle that just fine already, AFAICS. We just do
not allow TImode at all (like most (all?) other 32-bit targets).
Segher