RE: [PATCH 03/11] softfloat: Introduce float_flag_inorm_denormal

[Michael Morrell]

Just curious.  What's the expected timeline to get these denormal patches in 
the tree?

-----Original Message-----
From: Richard Henderson <richard.henderson@linaro.org> 
Sent: Saturday, May 29, 2021 8:21 AM
To: Michael Morrell <mmorrell@tachyum.com>; qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org
Subject: Re: [PATCH 03/11] softfloat: Introduce float_flag_inorm_denormal

On 5/28/21 10:41 AM, Michael Morrell wrote:
> I'm probably missing something, but why do we need both 
> "float_flag_inorm_denormal" and "float_flag_iflush_denormal"?
> 
> Couldn't the code that sets these flags set just a single flag for all 
> denormal inputs and the code that checks these flags check that single flag 
> combined with the "flush_inputs_to_zero" flag to accomplish what the two 
> separate "input denormal" flags do?

The thing that you're missing is that many guests leave the accumulated 
softfloat exceptions in the float_status structure until the guest FPSCR 
register is read. Unless the guest needs to raise an exception immediately, 
there's no reason to do otherwise.

With this setup, you have no temporal connection between "any denormal" and 
"flush-to-zero is set", thus two flags.


r~