b468ed494a
In 39b2979a4 Pavel has kindly refined the implementation of a test in such a way that it doesn't trip up over this patch -- the test wishes to stimulate LLDBs presentation of line0 locations, rather than wanting to always step on line-zero on entry to artificial_location.c. As that's what was tripping up this change, reapply. Original commit message follows. [DWARF] Emit a worst-case prologue_end flag for pathological inputs (#107849) prologue_end usually indicates where the end of the function-initialization lies, and is where debuggers usually choose to put the initial breakpoint for a function. Our current algorithm piggy-backs it on the first available source-location: which doesn't necessarily have anything to do with the start of the function. To avoid this in heavily-optimised code that lacks many useful source locations, pick a worst-case "if all else fails" prologue_end location, of the first instruction that appears to do meaningful computation. It'll be given the function-scope line number, which should run-on from the start of the function anyway. This means if your code is completely inverted by the optimiser, you can at least put a breakpoint at the _start_ like you expect, even if it's difficult to then step through. This patch also attempts to preserve some good behaviour we have without optimisations -- at O0, if the prologue immediately falls into a loop body without any computation happening, then prologue_end lands at the start of that loop. This is desirable; but does mean we need to do more work to detect and support those situations.
116 lines
4.9 KiB
LLVM
116 lines
4.9 KiB
LLVM
; RUN: llc -O0 < %s | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
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target triple = "x86_64-apple-macosx10.6.7"
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;CHECK-LABEL: foo:
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;CHECK: .loc 1 2 11 prologue_end
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define i32 @foo(i32 %i) nounwind ssp !dbg !1 {
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entry:
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%i.addr = alloca i32, align 4
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%j = alloca i32, align 4
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store i32 %i, ptr %i.addr, align 4
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call void @llvm.dbg.declare(metadata ptr %i.addr, metadata !7, metadata !DIExpression()), !dbg !8
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call void @llvm.dbg.declare(metadata ptr %j, metadata !9, metadata !DIExpression()), !dbg !11
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store i32 2, ptr %j, align 4, !dbg !12
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%tmp = load i32, ptr %j, align 4, !dbg !13
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%inc = add nsw i32 %tmp, 1, !dbg !13
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store i32 %inc, ptr %j, align 4, !dbg !13
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%tmp1 = load i32, ptr %j, align 4, !dbg !14
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%tmp2 = load i32, ptr %i.addr, align 4, !dbg !14
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%add = add nsw i32 %tmp1, %tmp2, !dbg !14
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store i32 %add, ptr %j, align 4, !dbg !14
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%tmp3 = load i32, ptr %j, align 4, !dbg !15
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ret i32 %tmp3, !dbg !15
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}
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declare void @llvm.dbg.declare(metadata, metadata, metadata) nounwind readnone
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;CHECK-LABEL: main:
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;CHECK: .loc 1 8 2 prologue_end
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define i32 @main() nounwind ssp !dbg !6 {
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entry:
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%retval = alloca i32, align 4
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store i32 0, ptr %retval, !dbg !22
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%call = call i32 @foo(i32 21), !dbg !16
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ret i32 %call, !dbg !16
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}
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;; int foo(int arg) {
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;; while (arg)
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;; arg--;
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;; return 0;
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;; }
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;;
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;; In this function, the entry block will fall through to while.cond, with no
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;; instructions having source-locations. The expectations at -O0 is that we'll
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;; put prologue_end on the first instruction of the loop, after %arg.addr is
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;; initialized.
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; CHECK: _bar:
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; CHECK-NEXT: Lfunc_begin2:
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; CHECK-NEXT: .loc 1 11 0 is_stmt 1
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; CHECK-NEXT: .cfi_startproc
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; CHECK-NEXT: ## %bb.0:
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; CHECK-NEXT: movl %edi, -4(%rsp)
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; CHECK-NEXT: LBB2_1:
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; CHECK-NEXT: ## =>This Inner Loop Header: Depth=1
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; CHECK-NEXT: Ltmp4:
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; CHECK-NEXT: .loc 1 12 3 prologue_end
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; CHECK-NEXT: cmpl $0, -4(%rsp)
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define dso_local i32 @bar(i32 noundef %arg) !dbg !30 {
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entry:
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%arg.addr = alloca i32, align 4
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store i32 %arg, ptr %arg.addr, align 4
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br label %while.cond, !dbg !37
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while.cond: ; preds = %while.body, %entry
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%0 = load i32, ptr %arg.addr, align 4, !dbg !38
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%tobool = icmp ne i32 %0, 0, !dbg !37
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br i1 %tobool, label %while.body, label %while.end, !dbg !37
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while.body: ; preds = %while.cond
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%1 = load i32, ptr %arg.addr, align 4, !dbg !39
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%dec = add nsw i32 %1, -1, !dbg !39
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store i32 %dec, ptr %arg.addr, align 4, !dbg !39
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br label %while.cond, !dbg !37
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while.end: ; preds = %while.cond
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ret i32 0, !dbg !42
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}
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!21}
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!18 = !{!1, !6}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.0 (trunk 131100)", isOptimized: false, emissionKind: FullDebug, file: !19, enums: !20, retainedTypes: !20, imports: null)
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!1 = distinct !DISubprogram(name: "foo", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 1, file: !19, scope: !2, type: !3)
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!2 = !DIFile(filename: "/tmp/a.c", directory: "/private/tmp")
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!3 = !DISubroutineType(types: !4)
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!4 = !{!5}
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!5 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
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!6 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, unit: !0, scopeLine: 7, file: !19, scope: !2, type: !3)
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!7 = !DILocalVariable(name: "i", line: 1, arg: 1, scope: !1, file: !2, type: !5)
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!8 = !DILocation(line: 1, column: 13, scope: !1)
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!9 = !DILocalVariable(name: "j", line: 2, scope: !10, file: !2, type: !5)
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!10 = distinct !DILexicalBlock(line: 1, column: 16, file: !19, scope: !1)
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!11 = !DILocation(line: 2, column: 6, scope: !10)
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!12 = !DILocation(line: 2, column: 11, scope: !10)
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!13 = !DILocation(line: 3, column: 2, scope: !10)
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!14 = !DILocation(line: 4, column: 2, scope: !10)
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!15 = !DILocation(line: 5, column: 2, scope: !10)
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!16 = !DILocation(line: 8, column: 2, scope: !17)
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!17 = distinct !DILexicalBlock(line: 7, column: 12, file: !19, scope: !6)
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!19 = !DIFile(filename: "/tmp/a.c", directory: "/private/tmp")
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!20 = !{}
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!21 = !{i32 1, !"Debug Info Version", i32 3}
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!22 = !DILocation(line: 0, column: 0, scope: !17)
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!30 = distinct !DISubprogram(name: "bar", scope: !2, file: !2, line: 10, type: !3, scopeLine: 11, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !34)
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!34 = !{}
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!36 = !DILocation(line: 11, column: 13, scope: !30)
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!37 = !DILocation(line: 12, column: 3, scope: !30)
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!38 = !DILocation(line: 12, column: 10, scope: !30)
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!39 = !DILocation(line: 13, column: 8, scope: !30)
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!42 = !DILocation(line: 14, column: 3, scope: !30)
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