TheRock/compiler/amd-llvm/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir

# RUN: llc %s -start-after=livedebugvalues -o - | FileCheck %s
#
## Original code, compiled clang -O2 -g -c
## 
## void ext();
## int main(int argc, char **argv) {
##   if (argc == 1)
##     ext();
##   else
##     ext();
##    return 0;
## }
## 
## In the code sequence above, the call to ext is given line zero during
## optimisation, because the code is duplicated down all function paths thus
## gets merged. We get something like this as the output:
##
##   0:   50                      push   %rax
##   1:   31 c0                   xor    %eax,%eax
##   3:   e8 00 00 00 00          call   8 <main+0x8>
##   4: R_X86_64_PLT32       ext-0x4
##   8:   31 c0                   xor    %eax,%eax
##   a:   59                      pop    %rcx
##   b:   c3                      ret
##
## And we could choose to set prologue_end on address 8, the clearing of the
## return register, because it's the first "real" instruction that isn't line
## zero. But this then causes debuggers to skip over the call instruction when
## entering the function, which is catastrophic.
##
## Instead: force the call itself to have a source location (the function scope
## line number), and put a prologue_end there. While it's not the original
## source of the call, it's better to have a prologue_end that means we'll stop
## in the prologue than to step over the call. This gives consumers the
## opportunity to recognise "this is a crazy function" and act accordingly.
##
## Check lines: ensure that we set prologue_end. The first entry is the
## start-of-function scope line, the second entry is the prologue_end on the
## call.
#
#
# CHECK:         main:
# CHECK-NEXT:    .Lfunc_begin0:
# CHECK-NEXT:        .file   0 "/tmp/test.c"
# CHECK-NEXT:        .loc    0 2 0
# CHECK-NEXT:        .cfi_startproc
# CHECK-NEXT:    # %bb.0:
# CHECK-NEXT:        pushq   %rax
# CHECK-NEXT:        .cfi_def_cfa_offset 16
# CHECK-NEXT:    .Ltmp0:
# CHECK-NEXT:        .loc    0 0 0 is_stmt 0
# CHECK-NEXT:        xorl    %eax, %eax
# CHECK-NEXT:        .loc    0 2 0 prologue_end is_stmt 1
# CHECK-NEXT:        callq   ext@PLT

--- |
  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"
  target triple = "x86_64-unknown-linux-gnu"
  
  ; Function Attrs: nounwind uwtable
  define dso_local noundef i32 @main(i32 noundef %argc, ptr noundef readnone captures(none) %argv) local_unnamed_addr !dbg !10 {
  entry:
    tail call void (...) @ext(), !dbg !22
    ret i32 0, !dbg !24
  }
  
  declare !dbg !25 void @ext(...) local_unnamed_addr
  
  !llvm.dbg.cu = !{!0}
  !llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
  !llvm.ident = !{!9}
  
  !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
  !1 = !DIFile(filename: "/tmp/test.c", directory: "")
  !2 = !{i32 7, !"Dwarf Version", i32 5}
  !3 = !{i32 2, !"Debug Info Version", i32 3}
  !4 = !{i32 1, !"wchar_size", i32 4}
  !5 = !{i32 8, !"PIC Level", i32 2}
  !6 = !{i32 7, !"PIE Level", i32 2}
  !7 = !{i32 7, !"uwtable", i32 2}
  !8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
  !9 = !{!"clang"}
  !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)
  !11 = !DIFile(filename: "/tmp/test.c", directory: "")
  !12 = !DISubroutineType(types: !13)
  !13 = !{!14, !14, !15}
  !14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
  !15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)
  !16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 64)
  !17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
  !18 = !{!19, !20}
  !19 = !DILocalVariable(name: "argc", arg: 1, scope: !10, file: !11, line: 2, type: !14)
  !20 = !DILocalVariable(name: "argv", arg: 2, scope: !10, file: !11, line: 2, type: !15)
  !21 = !DILocation(line: 0, scope: !10)
  !22 = !DILocation(line: 0, scope: !23)
  !23 = distinct !DILexicalBlock(scope: !10, file: !11, line: 3, column: 7)
  !24 = !DILocation(line: 7, column: 4, scope: !10, atomGroup: 2, atomRank: 1)
  !25 = !DISubprogram(name: "ext", scope: !11, file: !11, line: 1, type: !26, spFlags: DISPFlagOptimized)
  !26 = !DISubroutineType(types: !27)
  !27 = !{null}
...
---
name:            main
alignment:       16
tracksRegLiveness: true
noPhis:          true
isSSA:           false
noVRegs:         true
hasFakeUses:     false
debugInstrRef:   true
tracksDebugUserValues: true
frameInfo:
  stackSize:       8
  offsetAdjustment: -8
  maxAlignment:    1
  adjustsStack:    true
  hasCalls:        true
  maxCallFrameSize: 0
  isCalleeSavedInfoValid: true
machineFunctionInfo:
  amxProgModel:    None
body:             |
  bb.0.entry:
    frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
    frame-setup CFI_INSTRUCTION def_cfa_offset 16
    dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al,  debug-location !22
    CALL64pcrel32 target-flags(x86-plt) @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $al, implicit-def $rsp, implicit-def $ssp,  debug-location !22
    $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags,  debug-location !24
    $rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp,  debug-location !24
    frame-destroy CFI_INSTRUCTION def_cfa_offset 8,  debug-location !24
    RET64 $eax,  debug-location !24
...