Commit e2b838dd authored by Jeremy Morse's avatar Jeremy Morse
Browse files

[DebugInfo][InstrRef] Accept landingpad block arguments 

This patch makes instruction-referencing accepts an additional scenario
where values can be read from physical registers at the start of blocks. As
far as I was aware, this only happened:
 * With arguments in the entry block,
 * With constant physical registers,

To which this patch adds a third case:
 * With exception-handling landing-pad blocks

In the attached test: the operand of the dbg.value traces back to the
"landingpad" instruction, which becomes some copies from physregs. Right
now, that's deemed unacceptable, and the assertion fires. The fix is to
just accept this scenario; this is a case where the value in question is
defined by a register and a position, not by an instruction that defines
it. Reading it with a DBG_PHI is the correct behaviour, there isn't a
non-copy instruction that we can refer to.

Differential Revision: https://reviews.llvm.org/D109005
parent 25682868

llvm/lib/CodeGen/MachineFunction.cpp

+4 −4
Original line number Diff line number Diff line
@@ -1148,11 +1148,11 @@ auto MachineFunction::salvageCopySSA(MachineInstr &MI) 
    // locations.

    ;

  } else {

    // Assert that this is the entry block. If it isn't, then there is some

    // code construct we don't recognise that deals with physregs across

    // blocks.

    // Assert that this is the entry block, or an EH pad. If it isn't, then

    // there is some code construct we don't recognise that deals with physregs

    // across blocks.

    assert(!State.first.isVirtual());

    assert(&*InsertBB.getParent()->begin() == &InsertBB);

    assert(&*InsertBB.getParent()->begin() == &InsertBB || InsertBB.isEHPad());

  }



  // Create DBG_PHI for specified physreg.

llvm/test/DebugInfo/X86/instr-ref-eh-landing-pad.ll

0 → 100644
+92 −0
Original line number Diff line number Diff line 
; RUN: llc %s -stop-before=finalize-isel -o -\

; RUN:     -experimental-debug-variable-locations \

; RUN:   | FileCheck %s

;

; Test that instruction referencing variable locations can cope with exception

; landing pads. Variable locations can be derived from the ABI-defined arguments

; to landing-pad blocks, which should be treated much like argument locations.

; This gloriously simple piece of C++:

;

;    void a() try { a(); } catch (int *&) { }

;

; Produces the code below. A nameless variable is attached to the landing-pad

; record %0 (via %3), which salvages back to the entry to the landing pad. We

; should place a DBG_PHI at that point. Instead of crashing.

;

; CHECK-LABEL: bb.1.lpad (landing-pad):

; CHECK:       DBG_PHI $rax, 1

; CHECK-NEXT:  EH_LABEL



target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"

target triple = "x86_64-unknown-linux-gnu"



@_ZTIPi = external dso_local constant i8*



define dso_local void @_Z1av() local_unnamed_addr #0 personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) !dbg !8 {

entry:

  invoke void @_Z1av()

          to label %try.cont unwind label %lpad, !dbg !17



lpad:                                             ; preds = %entry

  %0 = landingpad { i8*, i32 }

          catch i8* bitcast (i8** @_ZTIPi to i8*), !dbg !19

  %1 = extractvalue { i8*, i32 } %0, 1, !dbg !19

  %2 = tail call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIPi to i8*)) #3, !dbg !20

  %matches = icmp eq i32 %1, %2, !dbg !20

  br i1 %matches, label %catch, label %eh.resume, !dbg !20



catch:                                            ; preds = %lpad

  %3 = extractvalue { i8*, i32 } %0, 0, !dbg !19

  %4 = tail call i8* @__cxa_begin_catch(i8* %3) #3, !dbg !20

  call void @llvm.dbg.value(metadata i8* %3, metadata !13, metadata !DIExpression(DW_OP_plus_uconst, 32, DW_OP_stack_value)), !dbg !21

  tail call void @__cxa_end_catch() #3, !dbg !22

  br label %try.cont, !dbg !22



try.cont:                                         ; preds = %entry, %catch

  ret void, !dbg !24



eh.resume:                                        ; preds = %lpad

  resume { i8*, i32 } %0, !dbg !20

}



declare dso_local i32 @__gxx_personality_v0(...)



; Function Attrs: nofree nosync nounwind readnone

declare i32 @llvm.eh.typeid.for(i8*) #1



declare dso_local i8* @__cxa_begin_catch(i8*) local_unnamed_addr



declare dso_local void @__cxa_end_catch() local_unnamed_addr



; Function Attrs: mustprogress nofree nosync nounwind readnone speculatable willreturn

declare void @llvm.dbg.value(metadata, metadata, metadata) #2



!llvm.dbg.cu = !{!0}

!llvm.module.flags = !{!3, !4, !5, !6}

!llvm.ident = !{!7}



!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)

!1 = !DIFile(filename: "test.cpp", directory: ".")

!2 = !{}

!3 = !{i32 7, !"Dwarf Version", i32 4}

!4 = !{i32 2, !"Debug Info Version", i32 3}

!5 = !{i32 1, !"wchar_size", i32 4}

!6 = !{i32 7, !"uwtable", i32 1}

!7 = !{!"clang"}

!8 = distinct !DISubprogram(name: "a", linkageName: "_Z1av", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)

!9 = !DIFile(filename: "test.cpp", directory: "")

!10 = !DISubroutineType(types: !11)

!11 = !{null}

!12 = !{!13}

!13 = !DILocalVariable(scope: !8, file: !9, line: 1, type: !14)

!14 = !DIDerivedType(tag: DW_TAG_reference_type, baseType: !15, size: 64)

!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)

!16 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)

!17 = !DILocation(line: 1, column: 16, scope: !18)

!18 = distinct !DILexicalBlock(scope: !8, file: !9, line: 1, column: 14)

!19 = !DILocation(line: 2, column: 1, scope: !18)

!20 = !DILocation(line: 1, column: 21, scope: !18)

!21 = !DILocation(line: 0, scope: !8)

!22 = !DILocation(line: 2, column: 1, scope: !23)

!23 = distinct !DILexicalBlock(scope: !8, file: !9, line: 1, column: 38)

!24 = !DILocation(line: 2, column: 1, scope: !8)