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Merge pull request #893 from hvitved/csharp/cfg/splitting-performance-tweaks
C#: CFG performance improvements
2 parents 937049e + e074dae commit 9319d66

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+487
-23
lines changed

4 files changed

+487
-23
lines changed

‎csharp/ql/src/semmle/code/csharp/controlflow/internal/Splitting.qll‎

Lines changed: 70 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -13,6 +13,9 @@ private import semmle.code.csharp.controlflow.Guards as Guards
1313
private import ControlFlow
1414
private import SuccessorTypes
1515

16+
/** The maximum number of splits allowed for a given node. */
17+
private int maxSplits() { result = 7 }
18+
1619
cached
1720
private module Cached {
1821
cached
@@ -41,11 +44,13 @@ private module Cached {
4144
TSplitsNil() or
4245
TSplitsCons(SplitInternal head, Splits tail) {
4346
exists(
44-
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, int rnk
45-
|
46-
case2aFromRank(pred, predSplits, succ, tail, c, rnk + 1)
47+
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, int rnk,
48+
int numberOfSplits
4749
|
50+
case2aFromRank(pred, predSplits, succ, tail, c, rnk + 1, numberOfSplits) and
4851
head = case2aSomeAtRank(pred, predSplits, succ, c, rnk)
52+
|
53+
numberOfSplits < maxSplits() or head.getKind().isMandatory()
4954
)
5055
}
5156

@@ -93,6 +98,13 @@ abstract class SplitKind extends TSplitKind {
9398
*/
9499
abstract int getListOrder();
95100

101+
/**
102+
* Holds if a split of this kind is mandatory. That is, a split of this kind must
103+
* be taken into account, regardless of whether we might exceed the maximum number
104+
* of splits (`maxSplits()`).
105+
*/
106+
abstract predicate isMandatory();
107+
96108
/**
97109
* Gets the rank of this split kind among all the split kinds that apply to
98110
* control flow element `cfe`. The rank is based on the order defined by
@@ -264,6 +276,8 @@ module FinallySplitting {
264276
private class FinallySplitKind extends SplitKind, TFinallySplitKind {
265277
override int getListOrder() { result = 0 }
266278

279+
override predicate isMandatory() { any() }
280+
267281
override string toString() { result = "Finally" }
268282
}
269283

@@ -415,6 +429,8 @@ module ExceptionHandlerSplitting {
415429
private class ExceptionHandlerSplitKind extends SplitKind, TExceptionHandlerSplitKind {
416430
override int getListOrder() { result = 1 }
417431

432+
override predicate isMandatory() { any() }
433+
418434
override string toString() { result = "ExceptionHandler" }
419435
}
420436

@@ -711,6 +727,8 @@ module BooleanSplitting {
711727
)
712728
}
713729

730+
override predicate isMandatory() { none() }
731+
714732
override string toString() { result = kind.toString() }
715733
}
716734

@@ -961,19 +979,28 @@ private module SuccSplits {
961979
)
962980
}
963981

982+
pragma[nomagic]
983+
private predicate entryOfKind(
984+
ControlFlowElement pred, ControlFlowElement succ, Completion c, SplitInternal split,
985+
SplitKind sk
986+
) {
987+
split.hasEntry(pred, succ, c) and
988+
sk = split.getKind()
989+
}
990+
964991
/** Holds if `succSplits` should not have a split of kind `sk`. */
965-
pragma[noinline]
992+
pragma[nomagic]
966993
private predicate case2aNoneOfKind(
967994
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, SplitKind sk
968995
) {
969996
// None inherited from predecessor
970997
case2aNoneInheritedOfKindForall(pred, predSplits, succ, c, sk, TSplitsNil()) and
971998
// None newly entered into
972-
not exists(SplitInternal split | split.hasEntry(pred, succ, c) | split.getKind() = sk)
999+
not entryOfKind(pred, succ, c, _, sk)
9731000
}
9741001

9751002
/** Holds if `succSplits` should not have a split of kind `sk` at rank `rnk`. */
976-
pragma[noinline]
1003+
pragma[nomagic]
9771004
private predicate case2aNoneAtRank(
9781005
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, int rnk
9791006
) {
@@ -982,27 +1009,42 @@ private module SuccSplits {
9821009
)
9831010
}
9841011

985-
/** Gets a split that should be in `succSplits`. */
9861012
pragma[nomagic]
987-
private SplitInternal case2aSome(
1013+
private SplitInternal case2auxGetAPredecessorSplit(
9881014
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c
9891015
) {
9901016
case2aux(pred, predSplits, succ, c) and
1017+
result = predSplits.getASplit()
1018+
}
1019+
1020+
/** Gets a split that should be in `succSplits`. */
1021+
pragma[nomagic]
1022+
private SplitInternal case2aSome(
1023+
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, SplitKind sk
1024+
) {
9911025
(
992-
result = predSplits.getASplit() and
1026+
// Inherited from predecessor
1027+
result = case2auxGetAPredecessorSplit(pred, predSplits, succ, c) and
9931028
result.hasSuccessor(pred, succ, c)
9941029
or
995-
result.hasEntry(pred, succ, c) and
996-
case2aNoneInheritedOfKindForall(pred, predSplits, succ, c, result.getKind(), TSplitsNil())
997-
)
1030+
// Newly entered into
1031+
exists(SplitKind sk0 |
1032+
case2aNoneInheritedOfKindForall(pred, predSplits, succ, c, sk0, TSplitsNil())
1033+
|
1034+
entryOfKind(pred, succ, c, result, sk0)
1035+
)
1036+
) and
1037+
sk = result.getKind()
9981038
}
9991039

10001040
/** Gets a split that should be in `succSplits` at rank `rnk`. */
1041+
pragma[nomagic]
10011042
SplitInternal case2aSomeAtRank(
10021043
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Completion c, int rnk
10031044
) {
1004-
result = case2aSome(pred, predSplits, succ, c) and
1005-
rnk = result.getKind().getListRank(succ)
1045+
exists(SplitKind sk | result = case2aSome(pred, predSplits, succ, c, sk) |
1046+
rnk = sk.getListRank(succ)
1047+
)
10061048
}
10071049

10081050
/**
@@ -1022,28 +1064,33 @@ private module SuccSplits {
10221064
*/
10231065
predicate case2aFromRank(
10241066
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Splits succSplits,
1025-
Completion c, int rnk
1067+
Completion c, int rnk, int numberOfSplits
10261068
) {
10271069
case2aux(pred, predSplits, succ, c) and
10281070
succSplits = TSplitsNil() and
1029-
rnk = max(any(SplitKind sk).getListRank(succ)) + 1
1071+
rnk = max(any(SplitKind sk).getListRank(succ)) + 1 and
1072+
numberOfSplits = 0
10301073
or
1031-
case2aFromRank(pred, predSplits, succ, succSplits, c, rnk + 1) and
1074+
case2aFromRank(pred, predSplits, succ, succSplits, c, rnk + 1, numberOfSplits) and
10321075
case2aNoneAtRank(pred, predSplits, succ, c, rnk)
10331076
or
1034-
exists(Splits mid, SplitInternal split |
1035-
split = case2aCons(pred, predSplits, succ, mid, c, rnk)
1077+
exists(Splits mid, SplitInternal split, int numberOfSplitsMid |
1078+
split = case2aCons(pred, predSplits, succ, mid, c, rnk, numberOfSplitsMid)
10361079
|
1037-
succSplits = TSplitsCons(split, mid)
1080+
if numberOfSplitsMid < maxSplits() or split.getKind().isMandatory()
1081+
then succSplits = TSplitsCons(split, mid) and numberOfSplits = numberOfSplitsMid + 1
1082+
else (
1083+
succSplits = mid and numberOfSplits = numberOfSplitsMid
1084+
)
10381085
)
10391086
}
10401087

10411088
pragma[noinline]
10421089
private SplitInternal case2aCons(
10431090
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Splits succSplits,
1044-
Completion c, int rnk
1091+
Completion c, int rnk, int numberOfSplits
10451092
) {
1046-
case2aFromRank(pred, predSplits, succ, succSplits, c, rnk + 1) and
1093+
case2aFromRank(pred, predSplits, succ, succSplits, c, rnk + 1, numberOfSplits) and
10471094
result = case2aSomeAtRank(pred, predSplits, succ, c, rnk)
10481095
}
10491096

@@ -1077,7 +1124,7 @@ private module SuccSplits {
10771124
ControlFlowElement pred, Splits predSplits, ControlFlowElement succ, Splits succSplits,
10781125
Completion c
10791126
) {
1080-
case2aFromRank(pred, predSplits, succ, succSplits, c, 1)
1127+
case2aFromRank(pred, predSplits, succ, succSplits, c, 1, _)
10811128
or
10821129
case2bForall(pred, predSplits, succ, c, TSplitsNil()) and
10831130
succSplits = TSplitsNil()

‎csharp/ql/test/library-tests/controlflow/splits/SplittingStressTest.cs‎

Lines changed: 169 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,169 @@
1+
class SplittingStressTest
2+
{
3+
void M(bool b1, bool b2, bool b3, bool b4, bool b5, bool b6, bool b7, bool b8, bool b9, bool b10, bool b11, bool b12, bool b13, bool b14, bool b15, bool b16, bool b17, bool b18, bool b19, bool b20, bool b21, bool b22, bool b23, bool b24, bool b25, bool b26, bool b27, bool b28, bool b29, bool b30, bool b31, bool b32, bool b33, bool b34, bool b35, bool b36, bool b37, bool b38, bool b39, bool b40)
4+
{
5+
if (b1)
6+
;
7+
if (b2)
8+
;
9+
if (b3)
10+
;
11+
if (b4)
12+
;
13+
if (b5)
14+
;
15+
if (b6)
16+
;
17+
if (b7)
18+
;
19+
if (b8)
20+
;
21+
if (b9)
22+
;
23+
if (b10)
24+
;
25+
if (b11)
26+
;
27+
if (b12)
28+
;
29+
if (b13)
30+
;
31+
if (b14)
32+
;
33+
if (b15)
34+
;
35+
if (b16)
36+
;
37+
if (b17)
38+
;
39+
if (b18)
40+
;
41+
if (b19)
42+
;
43+
if (b20)
44+
;
45+
if (b21)
46+
;
47+
if (b22)
48+
;
49+
if (b23)
50+
;
51+
if (b24)
52+
;
53+
if (b25)
54+
;
55+
if (b26)
56+
;
57+
if (b27)
58+
;
59+
if (b28)
60+
;
61+
if (b29)
62+
;
63+
if (b30)
64+
;
65+
if (b31)
66+
;
67+
if (b32)
68+
;
69+
if (b33)
70+
;
71+
if (b34)
72+
;
73+
if (b35)
74+
;
75+
if (b36)
76+
;
77+
if (b37)
78+
;
79+
if (b38)
80+
;
81+
if (b39)
82+
;
83+
if (b40)
84+
;
85+
; // 2^40 splits
86+
87+
if (b1)
88+
;
89+
if (b2)
90+
;
91+
if (b3)
92+
;
93+
if (b4)
94+
;
95+
if (b5)
96+
;
97+
if (b6)
98+
;
99+
if (b7)
100+
;
101+
if (b8)
102+
;
103+
if (b9)
104+
;
105+
if (b10)
106+
;
107+
if (b11)
108+
;
109+
if (b12)
110+
;
111+
if (b13)
112+
;
113+
if (b14)
114+
;
115+
if (b15)
116+
;
117+
if (b16)
118+
;
119+
if (b17)
120+
;
121+
if (b18)
122+
;
123+
if (b19)
124+
;
125+
if (b20)
126+
;
127+
if (b21)
128+
;
129+
if (b22)
130+
;
131+
if (b23)
132+
;
133+
if (b24)
134+
;
135+
if (b25)
136+
;
137+
if (b26)
138+
;
139+
if (b27)
140+
;
141+
if (b28)
142+
;
143+
if (b29)
144+
;
145+
if (b30)
146+
;
147+
if (b31)
148+
;
149+
if (b32)
150+
;
151+
if (b33)
152+
;
153+
if (b34)
154+
;
155+
if (b35)
156+
;
157+
if (b36)
158+
;
159+
if (b37)
160+
;
161+
if (b38)
162+
;
163+
if (b39)
164+
;
165+
if (b40)
166+
;
167+
;
168+
}
169+
}

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