23.12.5. FDIV

The thresholds for divide are simple and based only on the difference of the exponents of the dividend and the divisor. It is not possible in a divide operation for the significand to overflow and cause an increment of the exponent. However, it is possible for the significand to require a single bit left shift and the exponent to be decremented for normalization. To reduce logic complexity, the overflow ranges are the same as those of the LSA operations in FADD and FSUB. The underflow ranges include the minimum normal exponent, 0x01 for single-precision and 0x001 for double-precision. Table 23.10 shows the FDIV bounce thresholds. The exponent values shown in Table 23.10 are in biased format.

Table 23.10. FDIV bounce thresholds

Initial quotient exponent valueFloat valueCondition in full-compliance mode
DP[1]SP[2]SPDP
>0x7FF-DP overflow-Bounce
0x7FF-DP NaN or infinity-Bounce
0x7FE-DP maximum normal-Bounce
0x7FD-DP normal-Bounce
0x7FC-DP normal-Normal
>0x47F>0xFFSP overflowBounceNormal
0x47F0xFFSP NaN or infinityBounceNormal
0x47E0xFESP maximum normalBounceNormal
0x47D0xFDSP normalBounceNormal
0x47C0xFCSP normalNormalNormal
0x3FF0x7Fe = 0 bias value NormalNormal
0x3820x02SP normalNormalNormal
0x3810x01SP normalBounceNormal
0x3800x00SP subnormalBounceNormal
<0x380<0x00SP underflowBounceNormal
0x002-DP normal-Normal
0x001-DP normal-Bounce
0x000-DP subnormal-Bounce
<0x000-DP underflow-Bounce

[1] DP = double-precision.

[2] SP = single-precision.

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