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
|
; RUN: opt -S -passes=jump-threading %s | FileCheck %s
; When simplify a branch based on LVI predicates, we should replace the
; comparison itself with a constant (when possible) in case it's otherwise used.
define i32 @test(ptr %p) {
; CHECK-LABEL: @test
; CHECK: icmp eq
; CHECK-NEXT: br i1 %cmp, label %exit2, label %exit1
; CHECK-NOT: icmp ne
entry:
%cmp = icmp eq ptr %p, null
br i1 %cmp, label %is_null, label %not_null
is_null:
%cmp2 = icmp ne ptr %p, null
br i1 %cmp2, label %exit1, label %exit2
not_null:
%cmp3 = icmp ne ptr %p, null
br i1 %cmp3, label %exit1, label %exit2
exit1:
ret i32 0
exit2:
ret i32 1
}
declare void @use(i1)
; It would not be legal to replace %cmp2 (well, in this case it actually is,
; but that's a CSE problem, not a LVI/jump threading problem)
define i32 @test_negative(ptr %p) {
; CHECK-LABEL: @test
; CHECK: icmp ne
; CHECK: icmp eq
; CHECK-NEXT: br i1 %cmp, label %exit2, label %exit1
; CHECK-NOT: icmp ne
entry:
%cmp2 = icmp ne ptr %p, null
call void @use(i1 %cmp2)
%cmp = icmp eq ptr %p, null
br i1 %cmp, label %is_null, label %not_null
is_null:
br i1 %cmp2, label %exit1, label %exit2
not_null:
br i1 %cmp2, label %exit1, label %exit2
exit1:
ret i32 0
exit2:
ret i32 1
}
; In this case, we can remove cmp2 because it's otherwise unused
define i32 @test2(ptr %p) {
; CHECK-LABEL: @test
; CHECK-LABEL: entry:
; CHECK-NEXT: icmp eq
; CHECK-NEXT: br i1 %cmp, label %exit2, label %exit1
; CHECK-NOT: icmp ne
entry:
%cmp2 = icmp ne ptr %p, null
%cmp = icmp eq ptr %p, null
br i1 %cmp, label %is_null, label %not_null
is_null:
br i1 %cmp2, label %exit1, label %exit2
not_null:
br i1 %cmp2, label %exit1, label %exit2
exit1:
ret i32 0
exit2:
ret i32 1
}
|
