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Re: two-element struct performance (was: strict-aliasing and typedefs)
- From: Richard Henderson <rth at redhat dot com>
- To: law at redhat dot com
- Cc: Joe Buck <jbuck at synopsys dot com>, Gabriel Dos Reis <gdr at integrable-solutions dot net>, Brad Lucier <lucier at math dot purdue dot edu>, gcc at gcc dot gnu dot org
- Date: Fri, 20 Feb 2004 00:03:15 -0800
- Subject: Re: two-element struct performance (was: strict-aliasing and typedefs)
- References: <20030514152914.A12355@synopsys.com> <200402192316.i1JNGx5C021528@speedy.slc.redhat.com>
On Thu, Feb 19, 2004 at 04:16:59PM -0700, law@redhat.com wrote:
> Doing better would require that the tree-ssa optimizers know about ABI
> details for passing parameters and return values -- if it had that knowledge
> then it would know that the caller will provide a suitable memory location
> for the return value and we could use it directly instead of first building
> the return value in T.6.
I don't know that tree-ssa knowledge of ABI details is quite necessary.
I think if we'd performed the computation into a RESULT_DECL rather than
into a VAR_DECL temporary, that would effectively do the job since we
can arrange for the RESULT_DECL to have rtl appropriate for a caller
provided memory location.
r~