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Altera_Forum
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15 years ago

Do I need to set compile flag for Hardware Floating Point Custom Instruction Divider?

I added the hardware FPU into SOPC including divider. In the public.mk file the compile flag is: ALT_CFLAGS += -mcustom-fpu-cfg=60-1 ALT_LDFLAGS += -mcustom-fpu-cfg=60-1 So I have to set ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

The custom instruction numbers are allocated by the sopc builder when the instructions are added. It isn't possible to assign specific numbers to specific instructions (they can be reordered, but the numbers have to be contiguous and start from zero). This is all a complete PITA since it means that the instruction definitions can't easily be built into the compiler, nor put into a header file.

Worse still, if you have a sopc image with more than one nios, and you want different subsets of custom instructions on each cpu you are in deep trouble.