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Re: [Qemu-ppc] [Qemu-devel] [V2 PATCH 11/18] softfloat: Fix float64_to_u

From: Tom Musta
Subject: Re: [Qemu-ppc] [Qemu-devel] [V2 PATCH 11/18] softfloat: Fix float64_to_uint32
Date: Wed, 18 Dec 2013 12:23:16 -0600
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

On 12/18/2013 12:03 PM, Peter Maydell wrote:
> On 18 December 2013 17:32, Tom Musta <address@hidden> wrote:
>> On 12/17/2013 11:45 AM, Peter Maydell wrote:
>> This seems to assume that the only case where flags could be set in
>> float64_to_uint32 is the case where a large result is returned. Is
>> this really the case?
> No, all it's assuming is that if we have the out-of-range
> case then the only flag that should be set is Invalid.
> In the "result is correct" case we return v and don't
> modify the flags from what float64_to_uint64() has set.
> Do you think there are flags that should be allowed
> to be set by the conversion operation even if it is signaling
> Invalid because of out of range input? IEEE754-2008 section 7.1
> says "An invocation of [any operation except directly modifying
> the flags] might raise at most two status flags, overflow
> with inexact or underflow with inexact". That is, any operation
> might (1) raise no flags (2) raise just one flag (3) raise
> Overflow+Inexact (4) raise Underflow+Inexact.
> [QEMU/softfloat don't suport alternate exception handling
> so we can ignore the standard's verbiage about that.]
> There is also the softfloat-specific float_flag_input_denormal,
> but I think that is also fine because it will only be set by the
> operation if we're squashing input denormals to zero, in
> which case the float-to-int conversion must always successfully
> return zero (because we squashed the input to plus or minus
> zero).
> This is a bit complicated though, so maybe I missed a case?
> thanks
> -- PMM

I'm sorry Peter ... I misread your patch.  I see what you are doing

I'll use your pattern, retest and resubmit.

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