Encoding:

Format:

SEL.fmt 

SEL fd, fs, ft, fmt

Purpose:

Select floating point values with FPR condition

Description:

FPR[fd] =FPR[fd].bit0 ? FPR[ft] : FPR[fs]

SEL fmt is a select operation, with a condition input in FPR fd, and 2 data inputs in FPRs ft and fs.

• If the condition is true, the value of ft is written to fd.

• If the condition is false, the value of fs is written to fd.

The condition input is specified by FPR fd, and is overwritten by the result.

The condition is true only if bit 0 of the condition input FPR fd is set. Other bits are ignored.

This instruction has floating point formats S and D, but these specify only the width of the operands. SEL.S can be used for 32-bit W data, and SEL.D can be used for 64 bit L data.

This instruction does not cause data-dependent exceptions. It does not trap on NaNs. It does not set the FPU Cause bits.

Restrictions:

None

Availability and Compatibility:

SEL fmt is introduced by and required as of microMIPS32 Release 6.

Special Considerations:

Only formats S and D are valid. Other format values may be used to encode other instructions. Unused format encodings are required to signal the Reserved Instruction exception.

Operation:

tmp = ValueFPR(fd, UNINTERPRETED_WORD)
cond = tmp.bit0
if cond then
   tmp = ValueFPR(ft, fmt) 
else
   tmp = ValueFPR(fs, fmt)
endif
StoreFPR(fd, fmt, tmp)

Exceptions:

Coprocessor Unusable, Reserved Instruction

Floating Point Exceptions:

None