File: dse.ll

package info (click to toggle)
llvm-toolchain-14 1%3A14.0.6-12
  • links: PTS, VCS
  • area: main
  • in suites: bookworm
  • size: 1,496,180 kB
  • sloc: cpp: 5,593,972; ansic: 986,872; asm: 585,869; python: 184,223; objc: 72,530; lisp: 31,119; f90: 27,793; javascript: 9,780; pascal: 9,762; sh: 9,482; perl: 7,468; ml: 5,432; awk: 3,523; makefile: 2,538; xml: 953; cs: 573; fortran: 567
file content (62 lines) | stat: -rw-r--r-- 1,633 bytes parent folder | download | duplicates (4)
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
; RUN: opt -S -passes=dse < %s | FileCheck %s

declare void @f()
declare noalias i8* @malloc(i32) nounwind

define void @test_0() {
; CHECK-LABEL: @test_0(
  %m = call i8* @malloc(i32 24)
  tail call void @f() [ "unknown"(i8* %m) ]
; CHECK: store i8 -19, i8* %m
  store i8 -19, i8* %m
  ret void
}

define i8* @test_1() {
; CHECK-LABEL: @test_1(
  %m = call i8* @malloc(i32 24)
  tail call void @f() [ "unknown"(i8* %m) ]
  store i8 -19, i8* %m
  tail call void @f()
  store i8 101, i8* %m

; CHECK: tail call void @f() [ "unknown"(i8* %m) ]
; CHECK: store i8 -19, i8* %m
; CHECK: tail call void @f()
; CHECK: store i8 101, i8* %m

  ret i8* %m
}

define void @test_2() {
; Since the deopt operand bundle does not escape %m (see caveat below), it is
; legal to elide the final store that location.

; CHECK-LABEL: @test_2(
  %m = call i8* @malloc(i32 24)
  tail call void @f() [ "deopt"(i8* %m) ]
  store i8 -19, i8* %m
  ret void

; CHECK:  tail call void @f() [ "deopt"(i8* %m) ]
; CHECK-NEXT:  ret void
}

define i8* @test_3() {
; Since the deopt operand bundle does not escape %m (see caveat below), @f
; cannot observe the stores to %m

; CHECK-LABEL: @test_3(
  %m = call i8* @malloc(i32 24)
  tail call void @f() [ "deopt"(i8* %m) ]
  store i8 -19, i8* %m
  tail call void @f()
  store i8 101, i8* %m
  ret i8* %m
}


; Caveat: technically, %m can only escape if the calling function is deoptimized
; at the call site (i.e. the call returns to the "deopt" continuation).  Since
; the calling function body will be invalidated in that case, the calling
; function can be optimized under the assumption that %m does not escape.