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[DebugInfo] Emit DWARF reference for DIVariable 'count' in DISubrange

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Summary:
This patch implements the codegen of DWARF debug info for non-constant
'count' fields for DISubrange.

This is patch [2/3] in a series to extend LLVM's DISubrange Metadata
node to support debugging of C99 variable length arrays and vectors with
runtime length like the Scalable Vector Extension for AArch64. It is
also a first step towards representing more complex cases like arrays
in Fortran.

Reviewers: echristo, pcc, aprantl, dexonsmith, clayborg, kristof.beyls, dblaikie

Reviewed By: aprantl

Subscribers: fhahn, aemerson, rengolin, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D41696

llvm-svn: 323323
This commit is contained in:
Sander de Smalen 2018-01-24 13:35:54 +00:00
parent 5a41bfbb07
commit 993da0b6ad
3 changed files with 58 additions and 1 deletions
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1
lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
View File

@ -483,6 +483,7 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
bool Abstract) {
// Define variable debug information entry.
auto VariableDie = DIE::get(DIEValueAllocator, DV.getTag());
insertDIE(DV.getVariable(), VariableDie);
if (Abstract) {
applyVariableAttributes(DV, *VariableDie);

8
lib/CodeGen/AsmPrinter/DwarfUnit.cpp
View File

@ -1335,7 +1335,13 @@ void DwarfUnit::constructSubrangeDIE(DIE &Buffer, const DISubrange *SR,
if (DefaultLowerBound == -1 || LowerBound != DefaultLowerBound)
addUInt(DW_Subrange, dwarf::DW_AT_lower_bound, None, LowerBound);
if (Count != -1)
if (auto *CV = SR->getCount().dyn_cast<DIVariable*>()) {
// 'finishVariableDefinition' that creates the types for a variable is
// always called _after_ the DIEs for variables are created.
auto *CountVarDIE = getDIE(CV);
assert(CountVarDIE && "DIE for count is not yet instantiated");
addDIEEntry(DW_Subrange, dwarf::DW_AT_count, *CountVarDIE);
} else if (Count != -1)
// FIXME: An unbounded array should reference the expression that defines
// the array.
addUInt(DW_Subrange, dwarf::DW_AT_count, None, Count);

50
test/DebugInfo/Generic/disubrange.ll Normal file
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@ -0,0 +1,50 @@
; RUN: rm -rf %t %t2
; RUN: %llc_dwarf -O0 -filetype=obj < %s > %t
; RUN: llvm-dwarfdump -name=vla_expr %t > %t2
; RUN: llvm-dwarfdump -verbose %t >> %t2
; RUN: cat %t2 | FileCheck %s
; This test runs llvm-dwarfdump twice:
; - First to get the debug entry for 'vla_expr'.
; - Second to check that this is the entry referenced in DW_AT_count.
; This way the test does not depend on the order in which DW_TAG_variables
; are emitted.
; CHECK: [[NODE:[0-9a-zA-Zx]+]]: DW_TAG_variable [4]
; CHECK-NEXT: DW_AT_name {{.*}} "vla_expr"
; CHECK: DW_AT_count [DW_FORM_ref4] (cu + {{.*}} => {[[NODE]]})
define void @foo(i32 %n) !dbg !7 {
entry:
call void @llvm.dbg.value(metadata i32 %n, i64 0, metadata !12, metadata !19), !dbg !20
ret void, !dbg !21
}
declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 5.0.1", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "vla.c", directory: "/path/to")
!2 = !{}
!3 = !{i32 2, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{!"clang version 5.0.1"}
!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 20, type: !8, isLocal: false, isDefinition: true, scopeLine: 20, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !11)
!8 = !DISubroutineType(types: !9)
!9 = !{null, !10}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !{!12, !13, !15}
!12 = !DILocalVariable(name: "n", arg: 1, scope: !7, file: !1, line: 20, type: !10)
!13 = !DILocalVariable(name: "vla_expr", scope: !7, file: !1, line: 21, type: !14)
!14 = !DIBasicType(name: "long unsigned int", size: 64, encoding: DW_ATE_unsigned)
!15 = !DILocalVariable(name: "vla", scope: !7, file: !1, line: 21, type: !16)
!16 = !DICompositeType(tag: DW_TAG_array_type, baseType: !10, align: 32, elements: !17)
!17 = !{!18, !18}
!18 = !DISubrange(count: !13)
!19 = !DIExpression()
!20 = !DILocation(line: 20, column: 14, scope: !7)
!21 = !DILocation(line: 22, column: 1, scope: !7)