internal/core/adt: alternative algorithm for splitting trees

Introduce a different and simpler algorithm for
splitting conjunct trees.

See insertAndSkipConjuncts in conjunct.go for more details.

Fixes #3601

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I00e5e3697c9b4456bf0cccd2d6b08e748a31b993
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1205364
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Matthew Sackman <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl

cue/testdata/cycle/023_reentrance.txtar

@@ -68,7 +68,7 @@ Allocs: 70
 Retain: 0
 
 Unifications: 62
-Conjuncts:    212
+Conjuncts:    224
 Disjuncts:    0
 -- out/evalalpha --
 Errors:
@@ -138,7 +138,7 @@ diff old new
 -Conjuncts:    464
 -Disjuncts:    268
 +Unifications: 62
-+Conjuncts:    212
++Conjuncts:    224
 +Disjuncts:    0
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/cycle/builtins.txtar

@@ -136,7 +136,7 @@ Allocs: 193
 Retain: 0
 
 Unifications: 167
-Conjuncts:    664
+Conjuncts:    657
 Disjuncts:    28
 -- diff/-out/evalalpha/stats<==>+out/eval/stats --
 diff old new
@@ -158,7 +158,7 @@ diff old new
 -Conjuncts:    389
 -Disjuncts:    290
 +Unifications: 167
-+Conjuncts:    664
++Conjuncts:    657
 +Disjuncts:    28
 -- out/eval/stats --
 Leaks:  12

cue/testdata/cycle/comprehension.txtar

@@ -317,7 +317,7 @@ Allocs: 778
 Retain: 0
 
 Unifications: 498
-Conjuncts:    3595
+Conjuncts:    2977
 Disjuncts:    196
 -- out/evalalpha --
 Errors:
@@ -958,7 +958,7 @@ diff old new
 -Conjuncts:    2525
 -Disjuncts:    1404
 +Unifications: 498
-+Conjuncts:    3595
++Conjuncts:    2977
 +Disjuncts:    196
 -- out/eval/stats --
 Leaks:  50

cue/testdata/cycle/inline.txtar

@@ -153,14 +153,14 @@ inline: acrossFields: ok1: {
   }
 }
 -- out/evalalpha/stats --
-Leaks:  113
+Leaks:  137
 Freed:  0
 Reused: 0
-Allocs: 113
+Allocs: 137
 Retain: 0
 
-Unifications: 109
-Conjuncts:    588
+Unifications: 101
+Conjuncts:    509
 Disjuncts:    0
 -- diff/-out/evalalpha/stats<==>+out/eval/stats --
 diff old new
@@ -172,17 +172,17 @@ diff old new
 -Reused: 136
 -Allocs: 252
 -Retain: 834
-+Leaks:  113
++Leaks:  137
 +Freed:  0
 +Reused: 0
-+Allocs: 113
++Allocs: 137
 +Retain: 0
 
 -Unifications: 388
 -Conjuncts:    1307
 -Disjuncts:    707
-+Unifications: 109
-+Conjuncts:    588
++Unifications: 101
++Conjuncts:    509
 +Disjuncts:    0
 -- out/eval/stats --
 Leaks:  247

cue/testdata/cycle/inline_non_recursive.txtar

@@ -101,7 +101,7 @@ Allocs: 228
 Retain: 0
 
 Unifications: 183
-Conjuncts:    1009
+Conjuncts:    824
 Disjuncts:    0
 -- out/evalalpha --
 Errors:
@@ -249,7 +249,7 @@ diff old new
 -Conjuncts:    2813
 -Disjuncts:    1485
 +Unifications: 183
-+Conjuncts:    1009
++Conjuncts:    824
 +Disjuncts:    0
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new

cue/testdata/cycle/issue990.txtar

@@ -83,15 +83,15 @@ This seems to be the result of incorrect handling of disjunctions.
 -- diff/todo/p3 --
 Reordering
 -- out/evalalpha/stats --
-Leaks:  633
-Freed:  49
-Reused: 49
-Allocs: 633
+Leaks:  605
+Freed:  45
+Reused: 45
+Allocs: 605
 Retain: 0
 
 Unifications: 175
-Conjuncts:    2747
-Disjuncts:    100
+Conjuncts:    2668
+Disjuncts:    92
 -- out/evalalpha --
 Errors:
 out.subs: structural cycle:
@@ -258,18 +258,18 @@ diff old new
 -Reused: 3200
 -Allocs: 25
 -Retain: 26
-+Leaks:  633
-+Freed:  49
-+Reused: 49
-+Allocs: 633
++Leaks:  605
++Freed:  45
++Reused: 45
++Allocs: 605
 +Retain: 0
 
 -Unifications: 2577
 -Conjuncts:    12017
 -Disjuncts:    3244
 +Unifications: 175
-+Conjuncts:    2747
-+Disjuncts:    100
++Conjuncts:    2668
++Disjuncts:    92
 -- diff/-out/evalalpha<==>+out/eval --
 diff old new
 --- old