1
; RUN: opt < %s -analyze -block-freq | FileCheck %s
3
; A loop with multiple exits isn't irreducible. It should be handled
6
; CHECK-LABEL: Printing analysis {{.*}} for function 'multiexit':
7
; CHECK-NEXT: block-frequency-info: multiexit
8
define void @multiexit(i1 %x) {
9
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
13
; CHECK-NEXT: loop.1: float = 2.0,
15
br i1 %x, label %exit.1, label %loop.2, !prof !0
17
; CHECK-NEXT: loop.2: float = 1.75,
19
br i1 %x, label %exit.2, label %loop.1, !prof !1
21
; CHECK-NEXT: exit.1: float = 0.25,
25
; CHECK-NEXT: exit.2: float = 0.75,
29
; CHECK-NEXT: return: float = 1.0, int = [[ENTRY]]
34
!0 = !{!"branch_weights", i32 1, i32 7}
35
!1 = !{!"branch_weights", i32 3, i32 4}
37
; Irreducible control flow
38
; ========================
40
; LoopInfo defines a loop as a non-trivial SCC dominated by a single block,
41
; called the header. A given loop, L, can have sub-loops, which are loops
42
; within the subgraph of L that excludes the header.
44
; In addition to loops, -block-freq has limited support for irreducible SCCs,
45
; which are SCCs with multiple entry blocks. Irreducible SCCs are discovered
46
; on they fly, and modelled as loops with multiple headers.
48
; The headers of irreducible sub-SCCs consist of its entry blocks and all nodes
49
; that are targets of a backedge within it (excluding backedges within true
52
; -block-freq is currently designed to act like a block is inserted that
53
; intercepts all the edges to the headers. All backedges and entries point to
54
; this block. Its successors are the headers, which split the frequency
57
; There are a number of testcases below. Only the first two have detailed
63
; In this case c1 and c2 should have frequencies of 15/7 and 13/7,
64
; respectively. To calculate this, consider assigning 1.0 to entry, and
65
; distributing frequency iteratively (to infinity). At the first iteration,
66
; entry gives 3/4 to c1 and 1/4 to c2. At every step after, c1 and c2 give 3/4
67
; of what they have to each other. Somehow, all of it comes out to exit.
69
; c1 = 3/4 + 1/4*3/4 + 3/4*3^2/4^2 + 1/4*3^3/4^3 + 3/4*3^3/4^3 + ...
70
; c2 = 1/4 + 3/4*3/4 + 1/4*3^2/4^2 + 3/4*3^3/4^3 + 1/4*3^3/4^3 + ...
72
; Simplify by splitting up the odd and even terms of the series and taking out
73
; factors so that the infite series matches:
75
; c1 = 3/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
76
; + 3/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
77
; c2 = 1/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
78
; + 9/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
80
; c1 = 15/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
81
; c2 = 13/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
83
; Since this geometric series sums to 16/7:
88
; If we treat c1 and c2 as members of the same loop, the exit frequency of the
89
; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
90
; gives 28/7, or 4.0, which is nice confirmation of the math above.
92
; -block-freq currently treats the two nodes as equals.
93
define void @multientry(i1 %x) {
94
; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
95
; CHECK-NEXT: block-frequency-info: multientry
97
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
98
br i1 %x, label %c1, label %c2, !prof !2
101
; CHECK-NEXT: c1: float = 2.0,
102
; The "correct" answer is: float = 2.142857{{[0-9]*}},
103
br i1 %x, label %c2, label %exit, !prof !2
106
; CHECK-NEXT: c2: float = 2.0,
107
; The "correct" answer is: float = 1.857142{{[0-9]*}},
108
br i1 %x, label %c1, label %exit, !prof !2
111
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
115
!2 = !{!"branch_weights", i32 3, i32 1}
120
; In this case c1 and c2 should be treated as equals in a single loop. The
121
; exit frequency is 1/3, so the scaling factor for the loop should be 3.0. The
122
; loop is entered 2/3 of the time, and c1 and c2 split the total loop frequency
123
; evenly (1/2), so they should each have frequencies of 1.0 (3.0*2/3*1/2).
124
; Another way of computing this result is by assigning 1.0 to entry and showing
125
; that c1 and c2 should accumulate frequencies of:
127
; 1/3 + 2/9 + 4/27 + 8/81 + ...
128
; 2^0/3^1 + 2^1/3^2 + 2^2/3^3 + 2^3/3^4 + ...
130
; At the first step, c1 and c2 each get 1/3 of the entry. At each subsequent
131
; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
132
; infinite series sums to 1.
133
define void @crossloops(i2 %x) {
134
; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
135
; CHECK-NEXT: block-frequency-info: crossloops
137
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
138
switch i2 %x, label %exit [ i2 1, label %c1
139
i2 2, label %c2 ], !prof !3
142
; CHECK-NEXT: c1: float = 1.0,
143
switch i2 %x, label %exit [ i2 1, label %c1
144
i2 2, label %c2 ], !prof !3
147
; CHECK-NEXT: c2: float = 1.0,
148
switch i2 %x, label %exit [ i2 1, label %c1
149
i2 2, label %c2 ], !prof !3
152
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
156
!3 = !{!"branch_weights", i32 2, i32 2, i32 2}
158
; A true loop with irreducible control flow inside.
159
define void @loop_around_irreducible(i1 %x) {
160
; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
161
; CHECK-NEXT: block-frequency-info: loop_around_irreducible
163
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
167
; CHECK-NEXT: loop: float = 4.0, int = [[HEAD:[0-9]+]]
168
br i1 %x, label %left, label %right, !prof !4
171
; CHECK-NEXT: left: float = 8.0,
172
br i1 %x, label %right, label %loop.end, !prof !5
175
; CHECK-NEXT: right: float = 8.0,
176
br i1 %x, label %left, label %loop.end, !prof !5
179
; CHECK-NEXT: loop.end: float = 4.0, int = [[HEAD]]
180
br i1 %x, label %loop, label %exit, !prof !5
183
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
186
!4 = !{!"branch_weights", i32 1, i32 1}
187
!5 = !{!"branch_weights", i32 3, i32 1}
189
; Two unrelated irreducible SCCs.
190
define void @two_sccs(i1 %x) {
191
; CHECK-LABEL: Printing analysis {{.*}} for function 'two_sccs':
192
; CHECK-NEXT: block-frequency-info: two_sccs
194
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
195
br i1 %x, label %a, label %b, !prof !6
198
; CHECK-NEXT: a: float = 0.75,
199
br i1 %x, label %a.left, label %a.right, !prof !7
202
; CHECK-NEXT: a.left: float = 1.5,
203
br i1 %x, label %a.right, label %exit, !prof !6
206
; CHECK-NEXT: a.right: float = 1.5,
207
br i1 %x, label %a.left, label %exit, !prof !6
210
; CHECK-NEXT: b: float = 0.25,
211
br i1 %x, label %b.left, label %b.right, !prof !7
214
; CHECK-NEXT: b.left: float = 0.625,
215
br i1 %x, label %b.right, label %exit, !prof !8
218
; CHECK-NEXT: b.right: float = 0.625,
219
br i1 %x, label %b.left, label %exit, !prof !8
222
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
225
!6 = !{!"branch_weights", i32 3, i32 1}
226
!7 = !{!"branch_weights", i32 1, i32 1}
227
!8 = !{!"branch_weights", i32 4, i32 1}
229
; A true loop inside irreducible control flow.
230
define void @loop_inside_irreducible(i1 %x) {
231
; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_inside_irreducible':
232
; CHECK-NEXT: block-frequency-info: loop_inside_irreducible
234
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
235
br i1 %x, label %left, label %right, !prof !9
238
; CHECK-NEXT: left: float = 2.0,
239
br i1 %x, label %right, label %exit, !prof !10
242
; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
246
; CHECK-NEXT: loop: float = 6.0,
247
br i1 %x, label %loop, label %right.end, !prof !11
250
; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
251
br i1 %x, label %left, label %exit, !prof !10
254
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
257
!9 = !{!"branch_weights", i32 1, i32 1}
258
!10 = !{!"branch_weights", i32 3, i32 1}
259
!11 = !{!"branch_weights", i32 2, i32 1}
261
; Irreducible control flow in a branch that's in a true loop.
262
define void @loop_around_branch_with_irreducible(i1 %x) {
263
; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible':
264
; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible
266
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
270
; CHECK-NEXT: loop: float = 2.0, int = [[LOOP:[0-9]+]]
271
br i1 %x, label %normal, label %irreducible.entry, !prof !12
274
; CHECK-NEXT: normal: float = 1.5,
278
; CHECK-NEXT: irreducible.entry: float = 0.5, int = [[IRREDUCIBLE:[0-9]+]]
279
br i1 %x, label %left, label %right, !prof !13
282
; CHECK-NEXT: left: float = 1.0,
283
br i1 %x, label %right, label %irreducible.exit, !prof !12
286
; CHECK-NEXT: right: float = 1.0,
287
br i1 %x, label %left, label %irreducible.exit, !prof !12
290
; CHECK-NEXT: irreducible.exit: float = 0.5, int = [[IRREDUCIBLE]]
294
; CHECK-NEXT: loop.end: float = 2.0, int = [[LOOP]]
295
br i1 %x, label %loop, label %exit, !prof !13
298
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
301
!12 = !{!"branch_weights", i32 3, i32 1}
302
!13 = !{!"branch_weights", i32 1, i32 1}
304
; Irreducible control flow between two true loops.
305
define void @loop_around_branch_with_irreducible_around_loop(i1 %x) {
306
; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_branch_with_irreducible_around_loop':
307
; CHECK-NEXT: block-frequency-info: loop_around_branch_with_irreducible_around_loop
309
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
313
; CHECK-NEXT: loop: float = 3.0, int = [[LOOP:[0-9]+]]
314
br i1 %x, label %normal, label %irreducible, !prof !14
317
; CHECK-NEXT: normal: float = 2.0,
321
; CHECK-NEXT: irreducible: float = 1.0,
322
br i1 %x, label %left, label %right, !prof !15
325
; CHECK-NEXT: left: float = 2.0,
326
br i1 %x, label %right, label %loop.end, !prof !16
329
; CHECK-NEXT: right: float = 2.0, int = [[RIGHT:[0-9]+]]
333
; CHECK-NEXT: right.loop: float = 10.0,
334
br i1 %x, label %right.loop, label %right.end, !prof !17
337
; CHECK-NEXT: right.end: float = 2.0, int = [[RIGHT]]
338
br i1 %x, label %left, label %loop.end, !prof !16
341
; CHECK-NEXT: loop.end: float = 3.0, int = [[LOOP]]
342
br i1 %x, label %loop, label %exit, !prof !14
345
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
348
!14 = !{!"branch_weights", i32 2, i32 1}
349
!15 = !{!"branch_weights", i32 1, i32 1}
350
!16 = !{!"branch_weights", i32 3, i32 1}
351
!17 = !{!"branch_weights", i32 4, i32 1}
353
; An irreducible SCC with a non-header.
354
define void @nonheader(i1 %x) {
355
; CHECK-LABEL: Printing analysis {{.*}} for function 'nonheader':
356
; CHECK-NEXT: block-frequency-info: nonheader
358
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
359
br i1 %x, label %left, label %right, !prof !18
362
; CHECK-NEXT: left: float = 1.0,
363
br i1 %x, label %bottom, label %exit, !prof !19
366
; CHECK-NEXT: right: float = 1.0,
367
br i1 %x, label %bottom, label %exit, !prof !20
370
; CHECK-NEXT: bottom: float = 1.0,
371
br i1 %x, label %left, label %right, !prof !18
374
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
377
!18 = !{!"branch_weights", i32 1, i32 1}
378
!19 = !{!"branch_weights", i32 1, i32 3}
379
!20 = !{!"branch_weights", i32 3, i32 1}
381
; An irreducible SCC with an irreducible sub-SCC. In the current version of
382
; -block-freq, this means an extra header.
384
; This testcases uses non-trivial branch weights. The CHECK statements here
385
; will start to fail if we change -block-freq to be more accurate. Currently,
386
; loop headers are affected by the weight of their corresponding back edges.
387
define void @nonentry_header(i1 %x, i2 %y) {
388
; CHECK-LABEL: Printing analysis {{.*}} for function 'nonentry_header':
389
; CHECK-NEXT: block-frequency-info: nonentry_header
391
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
392
br i1 %x, label %left, label %right, !prof !21
395
; CHECK-NEXT: left: float = 0.14
396
br i1 %x, label %top, label %bottom, !prof !22
399
; CHECK-NEXT: right: float = 0.42
400
br i1 %x, label %top, label %bottom, !prof !22
403
; CHECK-NEXT: top: float = 8.43
404
switch i2 %y, label %exit [ i2 0, label %left
406
i2 2, label %bottom ], !prof !23
409
; CHECK-NEXT: bottom: float = 4.5,
413
; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
416
!21 = !{!"branch_weights", i32 2, i32 1}
417
!22 = !{!"branch_weights", i32 1, i32 1}
418
!23 = !{!"branch_weights", i32 8, i32 1, i32 3, i32 12}