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 = metadata !{metadata !"branch_weights", i32 1, i32 7}
35 !1 = metadata !{metadata !"branch_weights", i32 3, i32 4}
37 ; The current BlockFrequencyInfo algorithm doesn't handle multiple entrances
38 ; into a loop very well. The frequencies assigned to blocks in the loop are
39 ; predictable (and not absurd), but also not correct and therefore not worth
42 ; There are two testcases below.
44 ; For each testcase, I use a CHECK-NEXT/NOT combo like an XFAIL with the
45 ; granularity of a single check. If/when this behaviour is fixed, we'll know
46 ; about it, and the test should be updated.
51 ; In this case c1 and c2 should have frequencies of 15/7 and 13/7,
52 ; respectively. To calculate this, consider assigning 1.0 to entry, and
53 ; distributing frequency iteratively (to infinity). At the first iteration,
54 ; entry gives 3/4 to c1 and 1/4 to c2. At every step after, c1 and c2 give 3/4
55 ; of what they have to each other. Somehow, all of it comes out to exit.
57 ; 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 + ...
58 ; 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 + ...
60 ; Simplify by splitting up the odd and even terms of the series and taking out
61 ; factors so that the infite series matches:
63 ; c1 = 3/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
64 ; + 3/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
65 ; c2 = 1/4 *(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
66 ; + 9/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
68 ; c1 = 15/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
69 ; c2 = 13/16*(9^0/16^0 + 9^1/16^1 + 9^2/16^2 + ...)
71 ; Since this geometric series sums to 16/7:
76 ; If we treat c1 and c2 as members of the same loop, the exit frequency of the
77 ; loop as a whole is 1/4, so the loop scale should be 4. Summing c1 and c2
78 ; gives 28/7, or 4.0, which is nice confirmation of the math above.
80 ; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
81 ; returns 3/4 and 13/16, respectively. LoopInfo ignores edges between loops
82 ; (and doesn't see any loops here at all), and -block-freq ignores the
83 ; irreducible edge from c2 to c1.
85 ; CHECK-LABEL: Printing analysis {{.*}} for function 'multientry':
86 ; CHECK-NEXT: block-frequency-info: multientry
87 define void @multientry(i1 %x) {
88 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
90 br i1 %x, label %c1, label %c2, !prof !2
92 ; This is like a single-line XFAIL (see above).
94 ; CHECK-NOT: float = 2.142857{{[0-9]*}},
96 br i1 %x, label %c2, label %exit, !prof !2
98 ; This is like a single-line XFAIL (see above).
100 ; CHECK-NOT: float = 1.857142{{[0-9]*}},
102 br i1 %x, label %c1, label %exit, !prof !2
104 ; We still shouldn't lose any frequency.
105 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
113 ; In this case c1 and c2 should be treated as equals in a single loop. The
114 ; exit frequency is 1/3, so the scaling factor for the loop should be 3.0. The
115 ; loop is entered 2/3 of the time, and c1 and c2 split the total loop frequency
116 ; evenly (1/2), so they should each have frequencies of 1.0 (3.0*2/3*1/2).
117 ; Another way of computing this result is by assigning 1.0 to entry and showing
118 ; that c1 and c2 should accumulate frequencies of:
120 ; 1/3 + 2/9 + 4/27 + 8/81 + ...
121 ; 2^0/3^1 + 2^1/3^2 + 2^2/3^3 + 2^3/3^4 + ...
123 ; At the first step, c1 and c2 each get 1/3 of the entry. At each subsequent
124 ; step, c1 and c2 each get 1/3 of what's left in c1 and c2 combined. This
125 ; infinite series sums to 1.
127 ; However, assuming c1 precedes c2 in reverse post-order, the current algorithm
128 ; returns 1/2 and 3/4, respectively. LoopInfo ignores edges between loops (and
129 ; treats c1 and c2 as self-loops only), and -block-freq ignores the irreducible
130 ; edge from c2 to c1.
132 ; Below I use a CHECK-NEXT/NOT combo like an XFAIL with the granularity of a
133 ; single check. If/when this behaviour is fixed, we'll know about it, and the
134 ; test should be updated.
136 ; CHECK-LABEL: Printing analysis {{.*}} for function 'crossloops':
137 ; CHECK-NEXT: block-frequency-info: crossloops
138 define void @crossloops(i2 %x) {
139 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
141 switch i2 %x, label %exit [ i2 1, label %c1
142 i2 2, label %c2 ], !prof !3
144 ; This is like a single-line XFAIL (see above).
146 ; CHECK-NOT: float = 1.0,
148 switch i2 %x, label %exit [ i2 1, label %c1
149 i2 2, label %c2 ], !prof !3
151 ; This is like a single-line XFAIL (see above).
153 ; CHECK-NOT: float = 1.0,
155 switch i2 %x, label %exit [ i2 1, label %c1
156 i2 2, label %c2 ], !prof !3
158 ; We still shouldn't lose any frequency.
159 ; CHECK-NEXT: exit: float = 1.0, int = [[ENTRY]]
164 !2 = metadata !{metadata !"branch_weights", i32 3, i32 1}
165 !3 = metadata !{metadata !"branch_weights", i32 2, i32 2, i32 2}
167 ; A reducible loop with irreducible control flow inside should still have
168 ; correct exit frequency.
170 ; CHECK-LABEL: Printing analysis {{.*}} for function 'loop_around_irreducible':
171 ; CHECK-NEXT: block-frequency-info: loop_around_irreducible
172 define void @loop_around_irreducible(i1 %x) {
173 ; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
177 ; CHECK-NEXT: loop: float = [[HEAD:[0-9.]+]], int = [[HEADINT:[0-9]+]]
179 br i1 %x, label %left, label %right
183 br i1 %x, label %right, label %loop.end
187 br i1 %x, label %left, label %loop.end
189 ; CHECK-NEXT: loop.end: float = [[HEAD]], int = [[HEADINT]]
191 br i1 %x, label %loop, label %exit
193 ; CHECK-NEXT: float = 1.0, int = [[ENTRY]]