Does the altfp_inv_sqrt megafunction correctly calculate the inverse square root for all input values?

Description

Due to a problem in the Quartus® II software version 10.0 and later, the single-precision version of the ALTFP_INV_SQRT megafunction incorrectly calculates the inverse square root of 0x3F800001 (1.0000001). For this value, the megafunction incorrectly calculates the result as 0x3F000000 (0.5). This bug only occurs for this input value.

 

Resolution

This problem is fixed beginning with the Quartus II softwaren version 12.1.