llvm dev - Jan 2019 - What does "preds" mean in a .ll file?

Hi,

I see things like this. What does it mean? Is it documented somewhere? Thanks.

; preds = %for.body

https://llvm.org/docs/LangRef.html

; <label>:91:                                     ; preds = %88
  %92 = load i8**, i8*** @glob_complete_word.matches, align 8, !dbg !99798
  %93 = load i32, i32* @glob_complete_word.ind, align 4, !dbg !99799
  %94 = sext i32 %93 to i64, !dbg !99798
  %95 = getelementptr inbounds i8*, i8** %92, i64 %94, !dbg !99798
  %96 = load i8*, i8** %95, align 8, !dbg !99798
  br label %98, !dbg !99797

; <label>:97:                                     ; preds = %88
  br label %98, !dbg !99797


-- 
Regards,
Peng

It's a list of all the predecessor basic blocks for this particular basic
block.

On Sat, Jan 19, 2019 at 12:27 PM Peng Yu via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> I see things like this. What does it mean? Is it documented somewhere?
> Thanks.
>
> ; preds = %for.body
>
> https://llvm.org/docs/LangRef.html
>
> ; <label>:91:                                     ; preds = %88
>   %92 = load i8**, i8*** @glob_complete_word.matches, align 8, !dbg !99798
>   %93 = load i32, i32* @glob_complete_word.ind, align 4, !dbg !99799
>   %94 = sext i32 %93 to i64, !dbg !99798
>   %95 = getelementptr inbounds i8*, i8** %92, i64 %94, !dbg !99798
>   %96 = load i8*, i8** %95, align 8, !dbg !99798
>   br label %98, !dbg !99797
>
> ; <label>:97:                                     ; preds = %88
>   br label %98, !dbg !99797
>
>
> --
> Regards,
> Peng
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

-- 
Regards
Bhatu
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Hi,

I see "; preds = %2" in the following example. But I don't see
where
the %2 block is mentioned. Do you know where the %2 block is
mentioned? Thanks.

==> main.c <=/* vim: set noexpandtab tabstop=2: */
#include <stdio.h>

int i;

struct {
  int x;
  int y;
} a[10];

void print() {
  puts("Hello World!");
}

int main(int argc, char *argv[]) {
  ++i;
  if(i) {
    ++a[0].x;
    print();
    printf("%d\n", i);
    printf("%d\n", a[0].x);
  }
  return 0;
}

==> main.exe.0.0.preopt.ll <=; ModuleID =
'/Users/pengy/mrrdir/test/mac/llvm/langref/main.exe.0.0.preopt.bc'
source_filename = "ld-temp.o"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

%struct.anon = type { i32, i32 }

@.str = private unnamed_addr constant [13 x i8] c"Hello World!\00",
align 1
@i = common dso_local global i32 0, align 4, !dbg !0
@a = common dso_local global [10 x %struct.anon] zeroinitializer,
align 16, !dbg !6
@.str.1 = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1

; Function Attrs: noinline nounwind optnone uwtable
define dso_local void @print() #0 !dbg !20 {
  %1 = call i32 @puts(i8* getelementptr inbounds ([13 x i8], [13 x
i8]* @.str, i32 0, i32 0)), !dbg !23
  ret void, !dbg !24
}

declare i32 @puts(i8*) #1

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i32 @main(i32, i8**) #0 !dbg !25 {
  %3 = alloca i32, align 4
  %4 = alloca i32, align 4
  %5 = alloca i8**, align 8
  store i32 0, i32* %3, align 4
  store i32 %0, i32* %4, align 4
  call void @llvm.dbg.declare(metadata i32* %4, metadata !31, metadata
!DIExpression()), !dbg !32
  store i8** %1, i8*** %5, align 8
  call void @llvm.dbg.declare(metadata i8*** %5, metadata !33,
metadata !DIExpression()), !dbg !34
  %6 = load i32, i32* @i, align 4, !dbg !35
  %7 = add nsw i32 %6, 1, !dbg !35
  store i32 %7, i32* @i, align 4, !dbg !35
  %8 = load i32, i32* @i, align 4, !dbg !36
  %9 = icmp ne i32 %8, 0, !dbg !36
  br i1 %9, label %10, label %17, !dbg !38

; <label>:10:                                     ; preds = %2
  %11 = load i32, i32* getelementptr inbounds ([10 x %struct.anon],
[10 x %struct.anon]* @a, i64 0, i64 0, i32 0), align 16, !dbg !39
  %12 = add nsw i32 %11, 1, !dbg !39
  store i32 %12, i32* getelementptr inbounds ([10 x %struct.anon], [10
x %struct.anon]* @a, i64 0, i64 0, i32 0), align 16, !dbg !39
  call void @print(), !dbg !41
  %13 = load i32, i32* @i, align 4, !dbg !42
  %14 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x
i8], [4 x i8]* @.str.1, i32 0, i32 0), i32 %13), !dbg !43
  %15 = load i32, i32* getelementptr inbounds ([10 x %struct.anon],
[10 x %struct.anon]* @a, i64 0, i64 0, i32 0), align 16, !dbg !44
  %16 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x
i8], [4 x i8]* @.str.1, i32 0, i32 0), i32 %15), !dbg !45
  br label %17, !dbg !46

; <label>:17:                                     ; preds = %10, %2
  ret i32 0, !dbg !47
}

; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.declare(metadata, metadata, metadata) #2

declare i32 @printf(i8*, ...) #1

attributes #0 = { noinline nounwind optnone uwtable
"correctly-rounded-divide-sqrt-fp-math"="false"
"disable-tail-calls"="false"
"less-precise-fpmad"="false"
"no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false"
"no-jump-tables"="false"
"no-nans-fp-math"="false"
"no-signed-zeros-fp-math"="false"
"no-trapping-math"="false"
"stack-protector-buffer-size"="8"
"target-cpu"="x86-64"
"target-features"="+fxsr,+mmx,+sse,+sse2,+x87"
"unsafe-fp-math"="false"
"use-soft-float"="false" }
attributes #1 = {
"correctly-rounded-divide-sqrt-fp-math"="false"
"disable-tail-calls"="false"
"less-precise-fpmad"="false"
"no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false"
"no-nans-fp-math"="false"
"no-signed-zeros-fp-math"="false"
"no-trapping-math"="false"
"stack-protector-buffer-size"="8"
"target-cpu"="x86-64"
"target-features"="+fxsr,+mmx,+sse,+sse2,+x87"
"unsafe-fp-math"="false"
"use-soft-float"="false" }
attributes #2 = { nounwind readnone speculatable }

!llvm.dbg.cu = !{!2}
!llvm.ident = !{!16}
!llvm.module.flags = !{!17, !18, !19}

!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "i", scope: !2, file: !3, line:
4, type: !12, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3,
producer: "clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)",
isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums:
!4, globals: !5)
!3 = !DIFile(filename: "main.c", directory:
"/root/mrrdir/test/mac/llvm/langref")
!4 = !{}
!5 = !{!0, !6}
!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
!7 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line:
9, type: !8, isLocal: false, isDefinition: true)
!8 = !DICompositeType(tag: DW_TAG_array_type, baseType: !9, size: 640,
elements: !14)
!9 = distinct !DICompositeType(tag: DW_TAG_structure_type, file: !3,
line: 6, size: 64, elements: !10)
!10 = !{!11, !13}
!11 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !9, file:
!3, line: 7, baseType: !12, size: 32)
!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!13 = !DIDerivedType(tag: DW_TAG_member, name: "y", scope: !9, file:
!3, line: 8, baseType: !12, size: 32, offset: 32)
!14 = !{!15}
!15 = !DISubrange(count: 10)
!16 = !{!"clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)"}
!17 = !{i32 2, !"Dwarf Version", i32 4}
!18 = !{i32 2, !"Debug Info Version", i32 3}
!19 = !{i32 1, !"wchar_size", i32 4}
!20 = distinct !DISubprogram(name: "print", scope: !3, file: !3, line:
11, type: !21, isLocal: false, isDefinition: true, scopeLine: 11,
isOptimized: false, unit: !2, retainedNodes: !4)
!21 = !DISubroutineType(types: !22)
!22 = !{null}
!23 = !DILocation(line: 12, column: 3, scope: !20)
!24 = !DILocation(line: 13, column: 1, scope: !20)
!25 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line:
15, type: !26, isLocal: false, isDefinition: true, scopeLine: 15,
flags: DIFlagPrototyped, isOptimized: false, unit: !2, retainedNodes:
!4)
!26 = !DISubroutineType(types: !27)
!27 = !{!12, !12, !28}
!28 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !29, size: 64)
!29 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !30, size: 64)
!30 = !DIBasicType(name: "char", size: 8, encoding:
DW_ATE_signed_char)
!31 = !DILocalVariable(name: "argc", arg: 1, scope: !25, file: !3,
line: 15, type: !12)
!32 = !DILocation(line: 15, column: 14, scope: !25)
!33 = !DILocalVariable(name: "argv", arg: 2, scope: !25, file: !3,
line: 15, type: !28)
!34 = !DILocation(line: 15, column: 26, scope: !25)
!35 = !DILocation(line: 16, column: 3, scope: !25)
!36 = !DILocation(line: 17, column: 6, scope: !37)
!37 = distinct !DILexicalBlock(scope: !25, file: !3, line: 17, column: 6)
!38 = !DILocation(line: 17, column: 6, scope: !25)
!39 = !DILocation(line: 18, column: 5, scope: !40)
!40 = distinct !DILexicalBlock(scope: !37, file: !3, line: 17, column: 9)
!41 = !DILocation(line: 19, column: 5, scope: !40)
!42 = !DILocation(line: 20, column: 20, scope: !40)
!43 = !DILocation(line: 20, column: 5, scope: !40)
!44 = !DILocation(line: 21, column: 25, scope: !40)
!45 = !DILocation(line: 21, column: 5, scope: !40)
!46 = !DILocation(line: 22, column: 3, scope: !40)
!47 = !DILocation(line: 23, column: 3, scope: !25)

On Sat, Jan 19, 2019 at 1:02 AM Bhatu <CS12B1010 at iith.ac.in>
wrote:
>
> It's a list of all the predecessor basic blocks for this particular
basic block.
>
> On Sat, Jan 19, 2019 at 12:27 PM Peng Yu via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hi,
>>
>> I see things like this. What does it mean? Is it documented somewhere?
Thanks.
>>
>> ; preds = %for.body
>>
>> https://llvm.org/docs/LangRef.html
>>
>> ; <label>:91:                                     ; preds = %88
>>   %92 = load i8**, i8*** @glob_complete_word.matches, align 8, !dbg
!99798
>>   %93 = load i32, i32* @glob_complete_word.ind, align 4, !dbg !99799
>>   %94 = sext i32 %93 to i64, !dbg !99798
>>   %95 = getelementptr inbounds i8*, i8** %92, i64 %94, !dbg !99798
>>   %96 = load i8*, i8** %95, align 8, !dbg !99798
>>   br label %98, !dbg !99797
>>
>> ; <label>:97:                                     ; preds = %88
>>   br label %98, !dbg !99797
>>
>>
>> --
>> Regards,
>> Peng
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
> --
> Regards
> Bhatu


-- 
Regards,
Peng