1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
|
; RUN: llc -O2 -o - %s | FileCheck %s
target datalayout = "e-m:e-i64:64-n32:64"
target triple = "powerpc64le-grtev4-linux-gnu"
; Intended layout:
; The code for tail-duplication during layout will produce the layout:
; test1
; test2
; body1 (with copy of test2)
; body2
; exit
;CHECK-LABEL: tail_dup_break_cfg:
;CHECK: mr [[TAGREG:[0-9]+]], 3
;CHECK: andi. {{[0-9]+}}, [[TAGREG]], 1
;CHECK-NEXT: bc 12, 1, [[BODY1LABEL:[._0-9A-Za-z]+]]
;CHECK-NEXT: # %test2
;CHECK-NEXT: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 30, 30
;CHECK-NEXT: bne 0, [[BODY2LABEL:[._0-9A-Za-z]+]]
;CHECK: [[EXITLABEL:[._0-9A-Za-z]+]]: # %exit
;CHECK: blr
;CHECK-NEXT: [[BODY1LABEL]]
;CHECK: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 30, 30
;CHECK-NEXT: beq 0, [[EXITLABEL]]
;CHECK-NEXT: [[BODY2LABEL:[._0-9A-Za-z]+]]:
;CHECK: b [[EXITLABEL]]
define void @tail_dup_break_cfg(i32 %tag) {
entry:
br label %test1
test1:
%tagbit1 = and i32 %tag, 1
%tagbit1eq0 = icmp eq i32 %tagbit1, 0
br i1 %tagbit1eq0, label %test2, label %body1, !prof !1 ; %test2 more likely
body1:
call void @a()
call void @a()
call void @a()
call void @a()
br label %test2
test2:
%tagbit2 = and i32 %tag, 2
%tagbit2eq0 = icmp eq i32 %tagbit2, 0
br i1 %tagbit2eq0, label %exit, label %body2, !prof !1 ; %exit more likely
body2:
call void @b()
call void @b()
call void @b()
call void @b()
br label %exit
exit:
ret void
}
; The branch weights here hint that we shouldn't tail duplicate in this case.
;CHECK-LABEL: tail_dup_dont_break_cfg:
;CHECK: mr [[TAGREG:[0-9]+]], 3
;CHECK: andi. {{[0-9]+}}, [[TAGREG]], 1
;CHECK-NEXT: bc 4, 1, [[TEST2LABEL:[._0-9A-Za-z]+]]
;CHECK-NEXT: # %body1
;CHECK: [[TEST2LABEL]]: # %test2
;CHECK-NEXT: rlwinm. {{[0-9]+}}, [[TAGREG]], 0, 30, 30
;CHECK-NEXT: beq 0, [[EXITLABEL:[._0-9A-Za-z]+]]
;CHECK-NEXT: # %body2
;CHECK: [[EXITLABEL:[._0-9A-Za-z]+]]: # %exit
;CHECK: blr
define void @tail_dup_dont_break_cfg(i32 %tag) {
entry:
br label %test1
test1:
%tagbit1 = and i32 %tag, 1
%tagbit1eq0 = icmp eq i32 %tagbit1, 0
br i1 %tagbit1eq0, label %test2, label %body1, !prof !1 ; %test2 more likely
body1:
call void @a()
call void @a()
call void @a()
call void @a()
br label %test2
test2:
%tagbit2 = and i32 %tag, 2
%tagbit2eq0 = icmp ne i32 %tagbit2, 0
br i1 %tagbit2eq0, label %body2, label %exit, !prof !3 ; %body2 more likely
body2:
call void @b()
call void @b()
call void @b()
call void @b()
br label %exit
exit:
ret void
}
declare void @a()
declare void @b()
declare void @c()
declare void @d()
; This function arranges for the successors of %succ to have already been laid
; out. When we consider whether to lay out succ after bb and to tail-duplicate
; it, v and ret have already been placed, so we tail-duplicate as it removes a
; branch and strictly increases fallthrough
; CHECK-LABEL: tail_dup_no_succ
; CHECK: # %entry
; CHECK: # %v
; CHECK: # %ret
; CHECK: # %bb
; CHECK: # %succ
; CHECK: # %c
; CHECK: bl c
; CHECK: rlwinm. {{[0-9]+}}, {{[0-9]+}}, 0, 29, 29
; CHECK: beq
; CHECK: b
define void @tail_dup_no_succ(i32 %tag) {
entry:
%tagbit1 = and i32 %tag, 1
%tagbit1eq0 = icmp eq i32 %tagbit1, 0
br i1 %tagbit1eq0, label %v, label %bb, !prof !2 ; %v very much more likely
bb:
%tagbit2 = and i32 %tag, 2
%tagbit2eq0 = icmp eq i32 %tagbit2, 0
br i1 %tagbit2eq0, label %succ, label %c, !prof !3 ; %succ more likely
c:
call void @c()
call void @c()
br label %succ
succ:
%tagbit3 = and i32 %tag, 4
%tagbit3eq0 = icmp eq i32 %tagbit3, 0
br i1 %tagbit3eq0, label %ret, label %v, !prof !1 ; %u more likely
v:
call void @d()
call void @d()
br label %ret
ret:
ret void
}
!1 = !{!"branch_weights", i32 5, i32 3}
!2 = !{!"branch_weights", i32 95, i32 5}
!3 = !{!"branch_weights", i32 8, i32 3}
|
