why are multiply-accumulate insns not used when -mfp32 on mips

[Amker.Cheng]

HI:
   found mult-acc insns like madd.s/d are only used when -mfp64 is specified,
as to codes, there macros defined as:

#define ISA_HAS_FP4             ((ISA_MIPS4                             \
                                  || (ISA_MIPS32R2 && TARGET_FLOAT64)   \    
<------only float 64
                                  || ISA_MIPS64                         \
                                  || ISA_MIPS64R2)                      \
                                 && !TARGET_MIPS16)

#define ISA_HAS_FP_MADD4_MSUB4  ISA_HAS_FP4

why not use madd when fp32? Is there anything special with fp32?

any clarification? Thanks very much

-- 
Best Regards.