d0s3t3ch/RandomWOW
1
0
Fork 0
mirror of https://git.wownero.com/wownero/RandomWOW.git synced 2024-08-15 00:23:14 +00:00
Code Issues Projects Releases Wiki Activity

Reworked "FNEG" instruction to make ASIC optimizations more difficult

Browse source
This commit is contained in:
tevador 2019-02-13 00:01:34 +01:00
parent 376c868ca0
commit f76e8c2e20
11 changed files with 29 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

7
doc/isa-ops.md
View file

@ -48,11 +48,16 @@ Memory operands are loaded as 8-byte values from the address indicated by `src`.
|5/256|FADD_M|F|mem|`(dst0, dst1) = (dst0 + [src][0], dst1 + [src][1])`|
|20/256|FSUB_R|F|A|`(dst0, dst1) = (dst0 - src0, dst1 - src1)`|
|5/256|FSUB_M|F|mem|`(dst0, dst1) = (dst0 - [src][0], dst1 - [src][1])`|
|6/256|FNEG_R|F|-|`(dst0, dst1) = (-dst0, -dst1)`|
|6/256|FSCAL_R|F|-|<code>(dst0, dst1) = (-2<sup>x0</sup> * dst0, -2<sup>x1</sup> * dst1)</code>|
|20/256|FMUL_R|E|A|`(dst0, dst1) = (dst0 * src0, dst1 * src1)`|
|4/256|FDIV_M|E|mem|`(dst0, dst1) = (dst0 / [src][0], dst1 / [src][1])`|
|6/256|FSQRT_R|E|-|`(dst0, dst1) = (√dst0, √dst1)`|
#### FSCAL_R
This instruction negates the number and multiplies it by <code>2<sup>x</sup></code>. `x` is calculated by taking the 5 least significant digits of the biased exponent and interpreting them as a binary number using the digit set `{-1, +1}` as opposed to the traditional `{0, 1}`. The possible values of `x` are all odd numbers from -31 to +31.
The mathematical operation described above is equivalent to a bitwise XOR of the binary representation with the value of `0x81F0000000000000`.
#### Denormal and NaN values
Due to restrictions on the values of the floating point registers, no operation results in `NaN`.
`FDIV_M` can produce a denormal result. In that case, the result is set to `DBL_MIN = 2.22507385850720138309e-308`, which is the smallest positive normal number.