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Re: [patch, tree-ssa] PR54295 Incorrect value extension in widening multiply-accumulate
- From: Richard Earnshaw <rearnsha at arm dot com>
- To: Andrew Stubbs <ams at codesourcery dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Richard Sandiford <rsandifo at nildram dot co dot uk>
- Date: Fri, 17 Aug 2012 15:31:42 +0100
- Subject: Re: [patch, tree-ssa] PR54295 Incorrect value extension in widening multiply-accumulate
- References: <502E4F54.9040309@arm.com> <502E53A7.406@codesourcery.com>
On 17/08/12 15:22, Andrew Stubbs wrote:
> On 17/08/12 15:04, Richard Earnshaw wrote:
>> The fix is to make is_widening_mult_p note that it has been called with
>> a WIDEN_MULT_EXPR and rather than decompose the operands again, to
>> simply extract the existing operands, which have already been formulated
>> correctly for a widening multiply operation.
>
> As long as the existing test cases work, I think the only problem with
> this idea is if some architecture has a wider range of widening
> multiply-and-accumulate than it does plain widening multiply.
But surely in that case step1 wouldn't have applied and we'd then be
looking at a MULT_EXPR not a WIDEN_MULT_EXPR.
R.