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Why is the "fpu=mix" option not recommended for the HI7000/4?

Last Updated:05/17/2017

Question:

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

Answer:

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

On the HI7000/4, since the FPSCR of an executing task without TA_COP1 is the same as the FPSCR of the previous task with TA_COP1 (i.e., it delays in saving as a context), running the code to modify the FPSCR destroys 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 calculations are not performed. However, this consumes more 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