ast: reduce allocations in empty_comptime_const_expr

[spytheman]

Improve compiler performance a bit, by reducing the amount of small allocations, for creating ComptTimeConstValue(EmptyExpr(0)) for the default field values of the AST nodes.

_{Huly®: V_0.6-21756}

[spytheman]

Here is the comparison with master:

#0 22:50:02 ^ ast_reduce_allocation_in_empty_comptime_const_expr ~/code/v>./v run .github/workflows/compare_pr_to_master.v
==================================================================================================
Current git branch: ast_reduce_allocation_in_empty_comptime_const_expr, commit: 5b8d9e4
    Compiling new V executables from PR branch: ast_reduce_allocation_in_empty_comptime_const_expr, commit: 5b8d9e4 ...
CPU: 2.80s      Real: 2.51s     Elapsed: 0:02.51        RAM: 432596KB   ./v -o vnew1 cmd/v
CPU: 2.71s      Real: 2.48s     Elapsed: 0:02.48        RAM: 432612KB   ./vnew1 -o vnew2 cmd/v
CPU: 2.51s      Real: 2.73s     Elapsed: 0:02.73        RAM: 415988KB   ./vnew2 -no-parallel -o vnew cmd/v
CPU: 0.16s      Real: 0.18s     Elapsed: 0:00.18        RAM: 44944KB    ./vnew -no-parallel -o nhw_current.c examples/hello_world.v
CPU: 2.10s      Real: 2.31s     Elapsed: 0:02.31        RAM: 416024KB   ./vnew -no-parallel -o nv_current.c cmd/v
>Size of        nhw_current.c:      45403
>Size of         nv_current.c:    6184087
>Size of                 vnew:    9540136
Switched to branch 'master'
Your branch is up to date with 'origin/master'.
==================================================================================================
    Compiling old V executables from branch: master, commit: d9e505b ...
CPU: 2.73s      Real: 2.48s     Elapsed: 0:02.48        RAM: 432472KB   ./v -o vold1 cmd/v
CPU: 2.73s      Real: 2.48s     Elapsed: 0:02.48        RAM: 434032KB   ./vold1 -o vold2 cmd/v
CPU: 2.49s      Real: 2.72s     Elapsed: 0:02.72        RAM: 417368KB   ./vold2 -no-parallel -o vold cmd/v
CPU: 0.16s      Real: 0.18s     Elapsed: 0:00.18        RAM: 45168KB    ./vold -no-parallel -o ohw_master.c examples/hello_world.v
CPU: 2.10s      Real: 2.33s     Elapsed: 0:02.33        RAM: 417476KB   ./vold -no-parallel -o ov_master.c cmd/v
>Size of         ohw_master.c:      45403
>Size of          ov_master.c:    6183975
>Size of                 vold:    9539928
==================================================================================================
File sizes so far ...
>>>>>> size("  nhw_current.c") - size("   ohw_master.c") =      45403 -      45403 =          0
>>>>>> size("   nv_current.c") - size("    ov_master.c") =    6184087 -    6183975 =        112
>>>>>> size("           vnew") - size("           vold") =    9540136 -    9539928 =        208
Switched to branch 'ast_reduce_allocation_in_empty_comptime_const_expr'
==================================================================================================
    Measuring at PR branch: ast_reduce_allocation_in_empty_comptime_const_expr, commit: 5b8d9e4 ...
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.9% 1.02x faster 110.4ms ± σ:   0.1ms, 110.2ms…110.6ms `./vnew -check-syntax           examples/hello_world.v`
 >  2         base         112.6ms ± σ:   0.0ms, 112.5ms…112.6ms `./vold -check-syntax           examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -1.3% 1.01x faster 110.9ms ± σ:   0.3ms, 110.5ms…111.2ms `./vnew -check-syntax           examples/hello_world.v`
 >  2         base         112.3ms ± σ:   0.0ms, 112.2ms…112.3ms `./vold -check-syntax           examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.6% 1.02x faster 110.4ms ± σ:   0.1ms, 110.3ms…110.5ms `./vnew -check-syntax           examples/hello_world.v`
 >  2         base         112.3ms ± σ:   0.2ms, 112.0ms…112.4ms `./vold -check-syntax           examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.4% 1.01x faster 163.8ms ± σ:   0.2ms, 163.6ms…164.0ms `./vnew -check                  examples/hello_world.v`
 >  2         base         166.1ms ± σ:   0.2ms, 165.9ms…166.3ms `./vold -check                  examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -1.2% 1.01x faster 163.8ms ± σ:   0.1ms, 163.7ms…163.9ms `./vnew -check                  examples/hello_world.v`
 >  2         base         165.9ms ± σ:   0.2ms, 165.6ms…166.2ms `./vold -check                  examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.3% 1.01x faster 163.5ms ± σ:   0.2ms, 163.4ms…163.8ms `./vnew -check                  examples/hello_world.v`
 >  2         base         165.7ms ± σ:   0.2ms, 165.6ms…166.0ms `./vold -check                  examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.0% 1.01x faster 183.6ms ± σ:   0.2ms, 183.4ms…183.8ms `./vnew -no-parallel -o nhw.c   examples/hello_world.v`
 >  2         base         185.5ms ± σ:   0.3ms, 185.2ms…185.8ms `./vold -no-parallel -o ohw.c   examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -1.6% 1.02x faster 183.0ms ± σ:   0.1ms, 183.0ms…183.1ms `./vnew -no-parallel -o nhw.c   examples/hello_world.v`
 >  2         base         186.0ms ± σ:   0.2ms, 185.8ms…186.3ms `./vold -no-parallel -o ohw.c   examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.5% 1.01x faster 183.5ms ± σ:   0.0ms, 183.5ms…183.5ms `./vnew -no-parallel -o nhw.c   examples/hello_world.v`
 >  2         base         186.2ms ± σ:   0.2ms, 186.0ms…186.3ms `./vold -no-parallel -o ohw.c   examples/hello_world.v`
>>>>>> size("          nhw.c") - size("          ohw.c") =      45403 -      45403 =          0
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.2% 1.01x faster 194.9ms ± σ:   0.1ms, 194.8ms…195.0ms `./vnew -no-parallel -o nhw.exe examples/hello_world.v`
 >  2         base         197.2ms ± σ:   0.3ms, 196.8ms…197.6ms `./vold -no-parallel -o ohw.exe examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -1.3% 1.01x faster 194.7ms ± σ:   0.1ms, 194.7ms…194.8ms `./vnew -no-parallel -o nhw.exe examples/hello_world.v`
 >  2         base         197.4ms ± σ:   0.2ms, 197.2ms…197.6ms `./vold -no-parallel -o ohw.exe examples/hello_world.v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.3% 1.01x faster 194.6ms ± σ:   0.1ms, 194.5ms…194.8ms `./vnew -no-parallel -o nhw.exe examples/hello_world.v`
 >  2         base         197.2ms ± σ:   0.1ms, 197.1ms…197.2ms `./vold -no-parallel -o ohw.exe examples/hello_world.v`
>>>>>> size("        nhw.exe") - size("        ohw.exe") =     242376 -     242376 =          0
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.4% 1.01x faster 915.5ms ± σ:   0.1ms, 915.5ms…915.7ms `./vnew -check-syntax           cmd/v`
 >  2         base         928.6ms ± σ:   1.0ms, 927.3ms…929.7ms `./vold -check-syntax           cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -1.6% 1.02x faster 915.1ms ± σ:   0.4ms, 914.6ms…915.5ms `./vnew -check-syntax           cmd/v`
 >  2         base         929.9ms ± σ:   0.6ms, 929.1ms…930.5ms `./vold -check-syntax           cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.6% 1.02x faster 914.2ms ± σ:   0.3ms, 913.8ms…914.4ms `./vnew -check-syntax           cmd/v`
 >  2         base         928.7ms ± σ:   0.7ms, 927.8ms…929.2ms `./vold -check-syntax           cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -1.0% 1.01x faster 1547.6ms ± σ:   0.4ms, 1547.1ms…1548.0ms `./vnew -check                  cmd/v`
 >  2         base         1564.0ms ± σ:   0.7ms, 1563.1ms…1564.8ms `./vold -check                  cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -0.9% 1.01x faster 1548.0ms ± σ:   1.0ms, 1546.5ms…1548.9ms `./vnew -check                  cmd/v`
 >  2         base         1562.4ms ± σ:   0.7ms, 1561.5ms…1563.1ms `./vold -check                  cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -1.1% 1.01x faster 1548.8ms ± σ:   0.0ms, 1548.8ms…1548.9ms `./vnew -check                  cmd/v`
 >  2         base         1565.9ms ± σ:   0.7ms, 1564.9ms…1566.5ms `./vold -check                  cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -0.7% 1.01x faster 2315.3ms ± σ:   0.5ms, 2314.9ms…2316.0ms `./vnew -no-parallel -o nv.c    cmd/v`
 >  2         base         2331.2ms ± σ:   0.4ms, 2331.0ms…2331.8ms `./vold -no-parallel -o ov.c    cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -0.6% 1.01x faster 2315.4ms ± σ:   0.2ms, 2315.2ms…2315.7ms `./vnew -no-parallel -o nv.c    cmd/v`
 >  2         base         2329.6ms ± σ:   1.5ms, 2327.6ms…2331.0ms `./vold -no-parallel -o ov.c    cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -0.7% 1.01x faster 2314.9ms ± σ:   1.1ms, 2313.9ms…2316.5ms `./vnew -no-parallel -o nv.c    cmd/v`
 >  2         base         2330.8ms ± σ:   0.3ms, 2330.4ms…2331.0ms `./vold -no-parallel -o ov.c    cmd/v`
>>>>>> size("           nv.c") - size("           ov.c") =    6184087 -    6184087 =          0
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  1
    1   -0.7% 1.01x faster 2709.5ms ± σ:   0.8ms, 2708.4ms…2710.4ms `./vnew -no-parallel -o nv.exe  cmd/v`
 >  2         base         2727.2ms ± σ:   0.4ms, 2726.9ms…2727.7ms `./vold -no-parallel -o ov.exe  cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  2
    1   -0.7% 1.01x faster 2710.8ms ± σ:   1.3ms, 2709.4ms…2712.4ms `./vnew -no-parallel -o nv.exe  cmd/v`
 >  2         base         2729.4ms ± σ:   0.2ms, 2729.2ms…2729.6ms `./vold -no-parallel -o ov.exe  cmd/v`
Summary after 1 series x 10 runs (%s are relative to first command, or `base`), discard maxs:  7, repeat:  3
    1   -0.6% 1.01x faster 2710.6ms ± σ:   1.2ms, 2709.4ms…2712.2ms `./vnew -no-parallel -o nv.exe  cmd/v`
 >  2         base         2727.4ms ± σ:   0.1ms, 2727.3ms…2727.6ms `./vold -no-parallel -o ov.exe  cmd/v`
>>>>>> size("         nv.exe") - size("         ov.exe") =    9540136 -    9540136 =          0
Done. Total time: 610.594590796 s.
==================================================================================================
Final summary for file diff sizes on their own branches:
>>>>>> size("  nhw_current.c") - size("   ohw_master.c") =      45403 -      45403 =          0
>>>>>> size("   nv_current.c") - size("    ov_master.c") =    6184087 -    6183975 =        112
>>>>>> size("           vnew") - size("           vold") =    9540136 -    9539928 =        208
==================================================================================================
Final summary for file diff sizes for generated files on the *current* branch:
>>>>>> size("          nhw.c") - size("          ohw.c") =      45403 -      45403 =          0
>>>>>> size("           nv.c") - size("           ov.c") =    6184087 -    6184087 =          0
>>>>>> size("        nhw.exe") - size("        ohw.exe") =     242376 -     242376 =          0
>>>>>> size("         nv.exe") - size("         ov.exe") =    9540136 -    9540136 =          0
#0 23:00:15 ^ ast_reduce_allocation_in_empty_comptime_const_expr ~/code/v>