Take for instance these examples:

0xDF MOD[0b11] MOD=3 REG[0b001] RM[nnn]
0xDD MOD[mm] MOD!=3 REG[0b110] RM[nnn] mode16 66_prefix MODRM()
EVV 0x52 VF2 V0F38 MOD[mm] MOD!=3 REG[rrr] RM[nnn] MODRM() BCRC=0  
0x0F 0xAE MOD[mm] MOD!=3 REG[0b110] RM[nnn]  f3_refining_prefix     MODRM()  
VV1 0x44  V66 V0F3A  MOD[mm]  MOD!=3 REG[rrr] RM[nnn] MODRM() VL128 UIMM8()
0x0F 0x1C MOD[mm] MOD!=3 REG[0b000] RM[nnn]  MODRM()  no_refining_prefix     CLDEMOTE=1
EVV 0x8A V66 V0F38 MOD[mm] MOD!=3 REG[rrr] RM[nnn] BCRC=0 MODRM()  VL512  W1  NOEVSR  ZEROING=0  ESIZE_64_BITS() NELEM_GSCAT()
EVV 0x2D VF2 V0F MOD[0b11] MOD=3 BCRC=0 REG[rrr] RM[nnn]  not64  NOEVSR  ZEROING=0 MASK=0  FIX_ROUND_LEN128()
0x0F 0x38 0xC9 MOD[mm] MOD!=3 REG[rrr] RM[nnn]  MODRM()  no_refining_prefix     

Where can I find in the code (or other docs) the meaning of all these things?

I understand what REG[0b110] means, and it seems that just calling MODRM() means "this has a ModR/M byte". But not sure.

• What MOD!=3 and MOD=3 mean.
• What the mm in MOD[mm] means. Same with REG[rrr] and RM[nnn].
• What the various flags mean, like not64 NOEVSR ZEROING=0 MASK=0.
• What the EVV and VV1 (and others) mean (not here in the code or in the Intel docs either).

The xed-state-bits.txt seems to encode the meaning of no_refining_prefix and others.

I've been looking through the generator.py for some hints, but not so much luck. The functions like NELEM_GSCAT() I am not sure what to make of (found in *-disp8.txt):

NELEM_GSCAT()::
otherwise -> nothing

Finally, is this PATTERN literally the order of bits to-be-found (or generated)? Or what should I be reading this as?

Thank you very much.