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From: Henri Cloetens <henri.cloetens@blueice.be>
Subject: Issue with frame pointer elimination
Message-ID: <d44bd081-a1cc-4de1-abb6-a69db2acfb6c@blueice.be>
Date: Thu, 4 Feb 2021 11:54:09 +0100
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Hello,

I am working on a custom gcc.9.2.0 back end, and have an issue with 
frame pointer elimination.

- the result is OK till step '276 : ira (register allocation)
- the result is NG from step '277 onward (reload)

What it did: It used R19 for the frame pointer. This register is 
call-clobbered, but is not used for
   argument passing. Some way, it assumed to be free, but it is not.

So, the frame pointer is put in it, it is call-clobbered, and the result 
is incorrect.

If the compile flag -fomit-frame-pointer is used, the issue goes away.

Has anybody any idea where to look ?.

Best Regards,

Henri.