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Re: numerical instability and estimate-probability
- From: Richard Henderson <rth at redhat dot com>
- To: mike stump <mrs at windriver dot com>
- Cc: gcc-pdo at atrey dot karlin dot mff dot cuni dot cz, gcc at gcc dot gnu dot org, jh at suse dot cz
- Date: Thu, 15 Nov 2001 17:39:03 -0800
- Subject: Re: numerical instability and estimate-probability
- References: <200111151931.LAA05450@kankakee.wrs.com>
On Thu, Nov 15, 2001 at 11:31:52AM -0800, mike stump wrote:
> It is advantageous to have gcc emit the same code, on different hosts
> for the same source code. This currently works.
No, it doesn't. We have code that is affected by the undefined
order of evaluation of function arguments. E.g.
foo (gen_reg_rtx (...), gen_reg_rtx (...))
Note that this is not a correctness issue -- we don't really care
what pseudo number is allocated to which register. However, the
pseudo number _does_ affect e.g. the order in which register
allocation considers pseudos for hard registers, which in turn
affects which hard registers are assigned.
r~