[llvm-dev] What does "preds" mean in a .ll file?
Craig Topper via llvm-dev
llvm-dev at lists.llvm.org
Sat Jan 19 13:32:51 PST 2019
Block %2 is the block that starts with the instruction %3 in your example.
If a basic block doesn’t have an explicit name provided it is given the
next available number. The unnamed arguments took %0 and %1 so the first
basic block which is unnamed took %2
If you use a debug build of the complete or pass -fno-discard-value-names
to clang there will be a lot more things named instead of just numbers.
On Sat, Jan 19, 2019 at 12:00 PM Peng Yu via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> 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
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
--
~Craig
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