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1# RUN: llc %s -start-after=livedebugvalues -o - | FileCheck %s2#3## Original code, compiled clang -O2 -g -c4## 5## void ext();6## int main(int argc, char **argv) {7## if (argc == 1)8## ext();9## else10## ext();11## return 0;12## }13## 14## In the code sequence above, the call to ext is given line zero during15## optimisation, because the code is duplicated down all function paths thus16## gets merged. We get something like this as the output:17##18## 0: 50 push %rax19## 1: 31 c0 xor %eax,%eax20## 3: e8 00 00 00 00 call 8 <main+0x8>21## 4: R_X86_64_PLT32 ext-0x422## 8: 31 c0 xor %eax,%eax23## a: 59 pop %rcx24## b: c3 ret25##26## And we could choose to set prologue_end on address 8, the clearing of the27## return register, because it's the first "real" instruction that isn't line28## zero. But this then causes debuggers to skip over the call instruction when29## entering the function, which is catastrophic.30##31## Instead: force the call itself to have a source location (the function scope32## line number), and put a prologue_end there. While it's not the original33## source of the call, it's better to have a prologue_end that means we'll stop34## in the prologue than to step over the call. This gives consumers the35## opportunity to recognise "this is a crazy function" and act accordingly.36##37## Check lines: ensure that we set prologue_end. The first entry is the38## start-of-function scope line, the second entry is the prologue_end on the39## call.40#41#42# CHECK: main:43# CHECK-NEXT: .Lfunc_begin0:44# CHECK-NEXT: .file 0 "/tmp/test.c"45# CHECK-NEXT: .loc 0 2 046# CHECK-NEXT: .cfi_startproc47# CHECK-NEXT: # %bb.0:48# CHECK-NEXT: pushq %rax49# CHECK-NEXT: .cfi_def_cfa_offset 1650# CHECK-NEXT: .Ltmp0:51# CHECK-NEXT: .loc 0 0 0 is_stmt 052# CHECK-NEXT: xorl %eax, %eax53# CHECK-NEXT: .loc 0 2 0 prologue_end is_stmt 154# CHECK-NEXT: callq ext@PLT55 56--- |57 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"58 target triple = "x86_64-unknown-linux-gnu"59 60 ; Function Attrs: nounwind uwtable61 define dso_local noundef i32 @main(i32 noundef %argc, ptr noundef readnone captures(none) %argv) local_unnamed_addr !dbg !10 {62 entry:63 tail call void (...) @ext(), !dbg !2264 ret i32 0, !dbg !2465 }66 67 declare !dbg !25 void @ext(...) local_unnamed_addr68 69 !llvm.dbg.cu = !{!0}70 !llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}71 !llvm.ident = !{!9}72 73 !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)74 !1 = !DIFile(filename: "/tmp/test.c", directory: "")75 !2 = !{i32 7, !"Dwarf Version", i32 5}76 !3 = !{i32 2, !"Debug Info Version", i32 3}77 !4 = !{i32 1, !"wchar_size", i32 4}78 !5 = !{i32 8, !"PIC Level", i32 2}79 !6 = !{i32 7, !"PIE Level", i32 2}80 !7 = !{i32 7, !"uwtable", i32 2}81 !8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}82 !9 = !{!"clang"}83 !10 = distinct !DISubprogram(name: "main", scope: !11, file: !11, line: 2, type: !12, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !18, keyInstructions: true)84 !11 = !DIFile(filename: "/tmp/test.c", directory: "")85 !12 = !DISubroutineType(types: !13)86 !13 = !{!14, !14, !15}87 !14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)88 !15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)89 !16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 64)90 !17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)91 !18 = !{!19, !20}92 !19 = !DILocalVariable(name: "argc", arg: 1, scope: !10, file: !11, line: 2, type: !14)93 !20 = !DILocalVariable(name: "argv", arg: 2, scope: !10, file: !11, line: 2, type: !15)94 !21 = !DILocation(line: 0, scope: !10)95 !22 = !DILocation(line: 0, scope: !23)96 !23 = distinct !DILexicalBlock(scope: !10, file: !11, line: 3, column: 7)97 !24 = !DILocation(line: 7, column: 4, scope: !10, atomGroup: 2, atomRank: 1)98 !25 = !DISubprogram(name: "ext", scope: !11, file: !11, line: 1, type: !26, spFlags: DISPFlagOptimized)99 !26 = !DISubroutineType(types: !27)100 !27 = !{null}101...102---103name: main104alignment: 16105tracksRegLiveness: true106noPhis: true107isSSA: false108noVRegs: true109hasFakeUses: false110debugInstrRef: true111tracksDebugUserValues: true112frameInfo:113 stackSize: 8114 offsetAdjustment: -8115 maxAlignment: 1116 adjustsStack: true117 hasCalls: true118 maxCallFrameSize: 0119 isCalleeSavedInfoValid: true120machineFunctionInfo:121 amxProgModel: None122body: |123 bb.0.entry:124 frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp125 frame-setup CFI_INSTRUCTION def_cfa_offset 16126 dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al, debug-location !22127 CALL64pcrel32 target-flags(x86-plt) @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $al, implicit-def $rsp, implicit-def $ssp, debug-location !22128 $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !24129 $rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !24130 frame-destroy CFI_INSTRUCTION def_cfa_offset 8, debug-location !24131 RET64 $eax, debug-location !24132...133