[WIP] Optimize the gcSections pass

[gkaracha]

No description provided.

[gkaracha]

Preliminary results

@TerrorJack, preliminary comparison between HEAD and master:

diff master/ahc.prof HEAD/ahc.prof shows:

<       total time  =        0.24 secs   (245 ticks @ 1000 us, 1 processor)
<       total alloc = 130,608,824 bytes  (excludes profiling overheads)
---
>       total time  =        0.24 secs   (244 ticks @ 1000 us, 1 processor)
>       total alloc = 132,291,880 bytes  (excludes profiling overheads)

diff master/ahc-link.prof HEAD/ahc-link.prof shows

<       total time  =       48.00 secs   (47998 ticks @ 1000 us, 1 processor)
<       total alloc = 3,320,867,416 bytes  (excludes profiling overheads)
---
>       total time  =       45.61 secs   (45606 ticks @ 1000 us, 1 processor)
>       total alloc = 3,320,989,152 bytes  (excludes profiling overheads)

diff master/ahc-ld.prof HEAD/ahc-ld.prof shows:

<       total time  =       32.17 secs   (32166 ticks @ 1000 us, 1 processor)
<       total alloc = 125,277,473,792 bytes  (excludes profiling overheads)
---
>       total time  =        9.68 secs   (9675 ticks @ 1000 us, 1 processor)
>       total alloc = 111,164,588,648 bytes  (excludes profiling overheads)

[gkaracha]

@TerrorJack I think it's ready for review now 🙂

[gkaracha]

master vs HEAD gives:
diff master/ahc.prof HEAD/ahc.prof:

<       total time  =        0.25 secs   (246 ticks @ 1000 us, 1 processor)
<       total alloc = 130,610,000 bytes  (excludes profiling overheads)
---
>       total time  =        0.28 secs   (283 ticks @ 1000 us, 1 processor)
>       total alloc = 132,159,648 bytes  (excludes profiling overheads)

diff master/ahc-link.prof HEAD/ahc-link.prof:

<       total time  =       45.99 secs   (45991 ticks @ 1000 us, 1 processor)
<       total alloc = 3,320,876,440 bytes  (excludes profiling overheads)
---
>       total time  =       47.77 secs   (47772 ticks @ 1000 us, 1 processor)
>       total alloc = 3,321,019,664 bytes  (excludes profiling overheads)

diff master/ahc-ld.prof HEAD/ahc-ld.prof :

<       total time  =       32.59 secs   (32585 ticks @ 1000 us, 1 processor)
<       total alloc = 125,276,180,272 bytes  (excludes profiling overheads)
---
>       total time  =       11.17 secs   (11166 ticks @ 1000 us, 1 processor)
>       total alloc = 111,162,737,872 bytes  (excludes profiling overheads)

I think this is good to go @TerrorJack! 🙂