FPU instruction question

zejiang0jason commented 6 years ago

Hi,

When I tried the FPU, I found double float instruction "fmv.d" in my image then the core ran to illegal instruction error. I guess this is because of the 'D' flag in toolchain build option "-march=IMFDXpulpv2". But when I changed to "-march=IMFXpulpv2", I got such build error

cc1: error: -march=IMFXpulpv2: single-precision-only is not yet supported

How can I configure the toolchain to remove the double float instructions? Thanks.

B.R. Zejiang

haugoug commented 6 years ago

Hi,

indeed there is a limitation of the toolchain which only supports both floats and doubles but not only floats. Until this is fixed, there are 2 work-arounds:

Either make sure that you have no double in your code by always using floats constants (e.g. 1.20f), calling float functions (e.g. cosf) and using only float type.
Or use this option to map doubles to floats: -mfpdouble=float . There is also this option available to have constants being floats: - -fsingle-precision-constant

Best,

Germain

On 24.08.2017 10:17, zejiangfish wrote:

Hi,

I found double float instruction "fmv.d" in my image then the core ran to illegal instruction error. I guess this is because of the 'D' flag in toolchain build option "-march=IMFDXpulpv2". But when I changed to "-march=IMFXpulpv2", I got such build error
cc1: error: -march=IMFXpulpv2: single-precision-only is not yet
supported
How can I configure the toolchain to remove the double float instructions? Thanks.

B.R. Zejiang

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zejiang0jason commented 6 years ago

Hi Germain,

Thanks a lot for your answer.

The work-around are workable but not so convenient, the code must be updated and not sure whether the functionality will be impacted.

Is there toolchain update plan for this?

Thanks again.

haugoug commented 6 years ago

Yes indeed this is just a temporary work-around, this is planned to get rid of this issue but I cannot tell yet when this is done.

Germain

On 24.08.2017 15:47, zejiangfish wrote:

Hi Germain,

Thanks a lot for your answer.

The work-around are workable but not so convenient, the code must be updated and not sure whether the functionality will be impacted.

Is there toolchain update plan for this?

Thanks again.

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zejiang0jason commented 6 years ago

Hi Germain,

OK, thanks.

pulp-platform / ri5cy_gnu_toolchain

FPU instruction question #9