1 ; RUN: opt < %s -analyze -block-freq | FileCheck %s
3 ; A loop with multiple exits should be handled correctly.
5 ; CHECK-LABEL: Printing analysis {{.*}} for function 'multiexit':
6 ; CHECK-NEXT: block-frequency-info: multiexit
7 define void @multiexit(i1 %x) {
8 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
12 ; CHECK-NEXT: loop.1: float = 1.333{{3*}},
14 br i1 %x, label %exit.1, label %loop.2, !prof !0
16 ; CHECK-NEXT: loop.2: float = 0.666{{6*7}},
18 br i1 %x, label %exit.2, label %loop.1, !prof !1
20 ; CHECK-NEXT: exit.1: float = 0.666{{6*7}},
24 ; CHECK-NEXT: exit.2: float = 0.333{{3*}},
28 ; CHECK-NEXT: return: float = 1.0, int = [[ENTRY]]
33 !0 = metadata !{metadata !"branch_weights", i32 3, i32 3}
34 !1 = metadata !{metadata !"branch_weights", i32 5, i32 5}
36 ; The current BlockFrequencyInfo algorithm doesn't handle multiple entrances
37 ; into a loop very well. The frequencies assigned to blocks in the loop are
38 ; predictable (and not absurd), but also not correct and therefore not worth
41 ; There are two testcases below.
43 ; For each testcase, I use a CHECK-NEXT/NOT combo like an XFAIL with the
44 ; granularity of a single check. If/when this behaviour is fixed, we'll know
45 ; about it, and the test should be updated.
50 ; In this case c1 and c2 should have frequencies of 15/7 and 13/7,
51 ; respectively. To calculate this, consider assigning 1.0 to entry, and
52 ; distributing frequency iteratively (to infinity). At the first iteration,
53 ; entry gives 3/4 to c1 and 1/4 to c2. At every step after, c1 and c2 give 3/4
54 ; of what they have to each other. Somehow, all of it comes out to exit.
56 ; 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 + ...
57 ; 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 + ...
59 ; Simplify by splitting up the odd and even terms of the series and taking out
60 ; factors so that the infite series matches:
62 ; c1 = 3/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
63 ; + 3/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
64 ; c2 = 1/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
65 ; + 9/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
67 ; c1 = 15/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
68 ; c2 = 13/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
70 ; Since this geometric series sums to 16/7:
75 ; If we treat c1 and c2 as members of the same loop, the exit frequency of the
76 ; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
77 ; gives 28/7, or 4.0, which is nice confirmation of the math above.
79 ; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
80 ; returns 3/4 and 13/16, respectively. LoopInfo ignores edges between loops
81 ; (and doesn't see any loops here at all), and -block-freq ignores the
82 ; irreducible edge from c2 to c1.
84 ; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
85 ; CHECK-NEXT: block-frequency-info: multientry
86 define void @multientry(i1 %x) {
87 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
89 br i1 %x, label %c1, label %c2, !prof !2
91 ; This is like a single-line XFAIL (see above).
93 ; CHECK-NOT: float = 2.142857{{[0-9]*}},
95 br i1 %x, label %c2, label %exit, !prof !2
97 ; This is like a single-line XFAIL (see above).
99 ; CHECK-NOT: float = 1.857142{{[0-9]*}},
101 br i1 %x, label %c1, label %exit, !prof !2
103 ; We still shouldn't lose any frequency.
104 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
112 ; In this case c1 and c2 should be treated as equals in a single loop. The
113 ; exit frequency is 1/3, so the scaling factor for the loop should be 3.0. The
114 ; loop is entered 2/3 of the time, and c1 and c2 split the total loop frequency
115 ; evenly (1/2), so they should each have frequencies of 1.0 (3.0*2/3*1/2).
116 ; Another way of computing this result is by assigning 1.0 to entry and showing
117 ; that c1 and c2 should accumulate frequencies of:
119 ; 1/3 + 2/9 + 4/27 + 8/81 + ...
120 ; 2^0/3^1 + 2^1/3^2 + 2^2/3^3 + 2^3/3^4 + ...
122 ; At the first step, c1 and c2 each get 1/3 of the entry. At each subsequent
123 ; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
124 ; infinite series sums to 1.
126 ; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
127 ; returns 1/2 and 3/4, respectively. LoopInfo ignores edges between loops (and
128 ; treats c1 and c2 as self-loops only), and -block-freq ignores the irreducible
129 ; edge from c2 to c1.
131 ; Below I use a CHECK-NEXT/NOT combo like an XFAIL with the granularity of a
132 ; single check. If/when this behaviour is fixed, we'll know about it, and the
133 ; test should be updated.
135 ; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
136 ; CHECK-NEXT: block-frequency-info: crossloops
137 define void @crossloops(i2 %x) {
138 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
140 switch i2 %x, label %exit [ i2 1, label %c1
141 i2 2, label %c2 ], !prof !3
143 ; This is like a single-line XFAIL (see above).
145 ; CHECK-NOT: float = 1.0,
147 switch i2 %x, label %exit [ i2 1, label %c1
148 i2 2, label %c2 ], !prof !3
150 ; This is like a single-line XFAIL (see above).
152 ; CHECK-NOT: float = 1.0,
154 switch i2 %x, label %exit [ i2 1, label %c1
155 i2 2, label %c2 ], !prof !3
157 ; We still shouldn't lose any frequency.
158 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
163 !2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
164 !3 = metadata !{metadata !"branch_weights", i32 2, i32 2, i32 2}
166 ; A reducible loop with irreducible control flow inside should still have
167 ; correct exit frequency.
169 ; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
170 ; CHECK-NEXT: block-frequency-info: loop_around_irreducible
171 define void @loop_around_irreducible(i1 %x) {
172 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
176 ; CHECK-NEXT: loop: float = [[HEAD:[0-9.]+]], int = [[HEADINT:[0-9]+]]
178 br i1 %x, label %left, label %right
182 br i1 %x, label %right, label %loop.end
186 br i1 %x, label %left, label %loop.end
188 ; CHECK-NEXT: loop.end: float = [[HEAD]], int = [[HEADINT]]
190 br i1 %x, label %loop, label %exit
192 ; CHECK-NEXT: float = 1.0, int = [[ENTRY]]