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Why is "fpu=mix" option not recommended for HI 7000/4

Last Updated:03/22/2017

Question:

In the HI7000/4 user’s manual, why is it mentioned that the usage of “fpu=mix” option is not recommended?

Answer:

With this option, the  compiler may  generate the code to modify the FPSCR even when floating-point calculation is not performed.

On the HI7000/4, since the FPSCR of an executing task without TA_COP1 is same as the FPSCR of the previous task with TA_COP1 (it delays in saving as a context), running the code to modify the FPSCR means to destroy the value of the FPSCR in the previous task with TA_COP1.  To avoid this, you may need to specify TA_COP1 even when floating-point calculation is not performed. However, this more consumes stack memory and takes more time for dispatching, compared to when TA_COP1 is not specified. This is why the option is not recommended.
Suitable Products
HI7000/4