Add FTEQCC pointer instructions

[divVerent]

This adds the following instructions:

• GLOBALADDRESS
• ADD_PIW
• LOADA_{F,V,S,ENT,FLD,FNC,I}
• LOAD_P
• LOADP_{F,V,S,ENT,FLD,FNC,I}
• Offset feature, and support for global pointers, for STOREP_{F,V,S,ENT,FLD,FNC,I}

It changes QC "address space" as follows:

• Before:
  • [0x0, num_ents * num_fields[: entities
• After:
  • [0x0, 0x80000000[: reserved (FTE puts strings and "malloc area" there)
  • [0x80000000, 0x80000000 + num_globals[: globals
  • [0x80000000 + num_globals, 0x80000000 + num_globals + num_ents * num_fields[: entities

This changes nothing visible, as these pointer values are generally invisible to well written QC code, however, writing to a NULL pointer notably now errors in the QC VM (previously, it would overwrite world.modelindex, which, I guess, may make the map go away, doesn't do that for me though).

Tested: this speeds up Xonotic serverbench by 6.8% while keeping correctness:

• Before/GMQCC: real 44.68 user 43.77 progs.dat size 6892660
• Before/FTEQCC: real 43.35 user 42.53 progs.dat size 6774526
• This/FTEQCC: real 41.87 user 40.96 progs.dat size 6436758

[divVerent]

To try with Xonotic, apply the attached patch, and compile like:

QCCFLAGS_WERROR='-O3' make -C data/xonotic-data.pk3dir/qcsrc ../progs.dat QCC=$HOME/Downloads/fteqw/build/fteqcc

use-new-opcodes-diff.txt

Note that there is one difference between fteqcc and gmqcc in constant folding; use this patch to remove this difference and get identical serverbench hashes so you can benchmark:

gmqcc-do-not-fold-into-reciprocal-diff.txt

Filed that as graphitemaster/gmqcc#210.

[divVerent]

@graphitemaster Any chance gmqcc could gain support for these opcodes as well (behind a flag), and then no longer emit array accessor functions?

[divVerent]

After having talked to @ladyhavoc, renamed FIELD_F etc. instruction in the disassembly to LOAD_F etc., matching the pr_comp.h names.

[divVerent]

From private chat, Spoike seems to be OK with this instruction set being added, and has plans of how to add it to FTEQCC.

So I am gonna merge now.

[Cloudwalk9]

Retroactive approval/LGTM from my end.