Encoding:

Format:

TRUNC.W.fmt 

TRUNC.W.S ft, fs

TRUNC.W.D ft, fs

Purpose:

Floating Point Truncate to Word Fixed Point

To convert an FP value to 32-bit fixed point, rounding toward zero.

Description:

 FPR[ft] = convert_and_round(FPR[fs])

The value in FPR fs, in format fmt, is converted to a value in 32-bit word fixed point format using rounding toward zero (rounding mode 1). The result is placed in FPR ft.

When the source value is Infinity, NaN, or rounds to an integer outside the range -2³¹ to 2³¹-1, the result cannot be represented correctly and an IEEE Invalid Operation condition exists. In this case the Invalid Operation flag is set in the FCSR. If the Invalid Operation Enable bit is set in the FCSR, no result is written to ft and an Invalid Operation exception is taken immediately. Otherwise, a default result is written to ft. On cores with FCSRNAN2008=0, the default result is 231-1. On cores with FCSRNAN2008=1, the default result is:

• 0 when the input value is NaN

2³¹-1 when the input value is +inf or rounds to a number larger than 2³¹-1

• -2³¹-1 when the input value is - or rounds to a number smaller than -2³¹-1

Restrictions:

The fields fs and ft must specify valid FPRs: fs for type fmt and fd for word fixed point. If the fields are not valid, the result is UNPREDICTABLE.

The operand must be a value in format fmt; if it is not, the result is UNPREDICTABLE and the value of the operand

FPR becomes UNPREDICTABLE.

Operation:

StoreFPR(ft, W, ConvertFmt(ValueFPR(fs, fmt), fmt, W))

Exceptions:

Coprocessor Unusable, Reserved Instruction

Floating Point Exceptions:

Inexact, Invalid Operation, Unimplemented Operation