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SubjectRe: pre egcs-1.1 testing and Linux 2.1.x
On Mon, 24 Aug 1998, Philip Blundell wrote:

>Precisely, and my objection to Andrea's patch was that it just disabled more
>optimisations, again to hide the bug.

Hmm, Philip you _could_ be right.

>Andrea wrote:
>
>>What I think is that the optimization code I commented out is buggy and
>>the bug is triggered by the regparm attribute.
>
>I think it's more subtle than that. The bug is not in the optimisations per
>se, it's in the register allocator and just happens to be provoked more often
>by higher optimisation (particularly when regparm is in use, because that
>increases register pressure significantly near function calls).

Are you sure? Did you tried it in practice? I thought that was the RTL
code generated by the optimization function (not arch dependent) that was
buggy:

GOOD RTL -> buggy optimization function -> BAD RTL

The RTL is arch indipendent.

As you say it could be also that:

GOOD RTL -> not buggy optimization function -> GOOD RTL 2

and that:

GOOD RTL -> buggy asm generator -> GOOD ASM

GOOD RTL 2 -> buggy asm generator -> BAD ASM

It should be trivial to understand this for a gcc hacker (it' s not for me
;-).

Andrea[s] Arcangeli


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