gcc porting: how to generate floating point multiply-add instruction?

[Jeff Law]

On 01/13/2016 09:01 AM, David Kang wrote:
>
>   Hello,
>
>   The hardware I'm porting gcc onto has floating multiply-add instructions.
> I'm trying to make gcc to generate the multiply-add instructions but it doesn't.
> I described the instruction in the .md file as follows:
A floating point multiply-add is generally going to be created by 
combining a floating point multiply and a floating point add in the 
combine.c pass.

Expanders are only used when they're explicitly called by name -- there 
is very little, if any support for generating multiply-add instructions 
prior to the combine phase in GCC.

Jeff