SPC58EC-DISP How to enable Floating-point multiply-add instructions

[Ethan_C]

Hi,

I tried to write a piece of code involving multiplication and addition (a*b+c) hoping the compiler would automatically use the FMA (fused multiply-add) instruction. However, it seems to still decompose it into separate instructions, efsadd and efsmul. I've attempted to use compiler options like -O3 or -ffpcontract=fast, but I haven't seen it compile into FMA instructions. I'd like to ask if FMA instructions are supported? (I've seen instructions like fmadd mentioned in the documentation).

Best regards,

[Giuseppe DI-GIORE · Accepted solution]

Hello,

the FMA instruction is included in PowerPC instruction set (see the Reference Manual for Book-E processors).

However is the compiler responsible for generating FMADD instruction.

Which compiler did you use for testing?

The Hightec PowerPC compiler (available here) by default generates float-multiple-add instructions.

If you use SPC5Studio, install the Hightec PowerPC compiler suite via SPC5Studio market place, then apply for license.

Best Regards.

[Ethan_C]

I'm using the FreeFCC compiler with VLE support as the default option. I'll try switching to Hightect and see how it goes. Thank you very much for your help.

Best regards,