[DebugInfo] DISubrange support for fortran assumed size array

[alok]

Summary

Summary:

This is needed to support assumed size array of fortran which can have missing upperBound/count,
contrary to current DISubrange support.

  Example:
  subroutine sub (array1, array2)
    integer :: array1 (*)
    integer :: array2 (4:9, 10:*)

    array1(7:8) = 9
    array2(5, 10) = 10
  end subroutine
  Now the validation check is relaxed for the Fortran.

Testing:

• check-llvm
• check-debuginfo

[aprantl]

llvm/lib/IR/Verifier.cpp

906

Can you add an isFortran helper function to Dwarf.h?

[alok]

llvm/lib/IR/Verifier.cpp

906

Thanks. I shall do that in next patch.

[alok]

Updated to incorporate @aprantl 's comment.

[aprantl]

llvm/include/llvm/BinaryFormat/Dwarf.h

288

This would trigger an unreachable for the interval (DW_LANG_lo_user, DW_LANG_hi_user). Why not just say default: false instead of trying to enumerate all non-Fortran languages?

[alok]

llvm/include/llvm/BinaryFormat/Dwarf.h

288

It was taken from function "isCPlusPlus", but I agree with you that it is better to return false for default and dont depend on llvm_unreachable to get assistance in adding new language enums. I shall update the patch.

[alok]

Updated to incorporate comment from @aprantl .

[aprantl]

I see

llvm/include/llvm/BinaryFormat/Dwarf.h

288

Oh, I see what you mean now! Unfortunately I consider isCplusPlus() to be well-intentioned but broken, too. We can't have an llvm_unreachable() on perfectly valid input. A compiler frontend using LLVM as a backend, or a LLDB loading a third-party binary must not crash when encountering a user constant.

To clarify: I think the idea that isCplusPlus uses to enumerate all constants to get the switch coverage warning is good and I'm fine with keeping the long explicit switch. We just cannot allow an llvm_unreachable for valid (or invalid!) inputs. This function is used by LLDB and you don't want the debugger to crash when loading a third-party object file.

[alok]

llvm/include/llvm/BinaryFormat/Dwarf.h

288

Thanks for your suggestion, I shall keep the long explicit switch without llvm_unreachable.

[alok]

Incorporated comment from @aprantl .

[aprantl]

Thank you!

llvm/include/llvm/BinaryFormat/Dwarf.h

235

Would you mind doing the same change here, too? There's no need start to another review for that.

[alok]

Thanks @aprantl for reviewing this. Any idea how to backport it and other fortran related commits to older version of LLVM (11, 10, 9) ?

llvm/include/llvm/BinaryFormat/Dwarf.h

inline bool isCPlusPlus(SourceLanguage S) {
   case DW_LANG_BLISS:
   case DW_LANG_Mips_Assembler:
   case DW_LANG_GOOGLE_RenderScript:
   case DW_LANG_BORLAND_Delphi:
   case DW_LANG_lo_user:
   case DW_LANG_hi_user:
     return false;
   }
   llvm_unreachable("Invalid source language");
 }
 
+inline bool isFortran(SourceLanguage S) {
+  // Deliberately enumerate all the language options so we get a warning when
+  // new language options are added (-Wswitch) that'll hopefully help keep this
+  // switch up-to-date when new Fortran versions are added.
+  switch (S) {
+  case DW_LANG_Fortran77:
+  case DW_LANG_Fortran90:
+  case DW_LANG_Fortran95:
+  case DW_LANG_Fortran03:
+  case DW_LANG_Fortran08:
+    return true;
+  case DW_LANG_C89:
+  case DW_LANG_C:
+  case DW_LANG_Ada83:
+  case DW_LANG_C_plus_plus:
+  case DW_LANG_Cobol74:
+  case DW_LANG_Cobol85:
+  case DW_LANG_Pascal83:
+  case DW_LANG_Modula2:
+  case DW_LANG_Java:
+  case DW_LANG_C99:
+  case DW_LANG_Ada95:
+  case DW_LANG_PLI:
+  case DW_LANG_ObjC:
+  case DW_LANG_ObjC_plus_plus:
+  case DW_LANG_UPC:
+  case DW_LANG_D:
+  case DW_LANG_Python:
+  case DW_LANG_OpenCL:
+  case DW_LANG_Go:
+  case DW_LANG_Modula3:
+  case DW_LANG_Haskell:
+  case DW_LANG_C_plus_plus_03:
+  case DW_LANG_C_plus_plus_11:
+  case DW_LANG_OCaml:
+  case DW_LANG_Rust:
+  case DW_LANG_C11:
+  case DW_LANG_Swift:
+  case DW_LANG_Julia:
+  case DW_LANG_Dylan:
+  case DW_LANG_C_plus_plus_14:
+  case DW_LANG_RenderScript:
+  case DW_LANG_BLISS:
+  case DW_LANG_Mips_Assembler:
+  case DW_LANG_GOOGLE_RenderScript:
+  case DW_LANG_BORLAND_Delphi:
+  case DW_LANG_lo_user:
+  case DW_LANG_hi_user:
+    return false;
+  }
+  llvm_unreachable("Invalid source language");
+}
+
 enum CaseSensitivity {
   // Identifier case codes
   DW_ID_case_sensitive = 0x00,
   DW_ID_up_case = 0x01,
   DW_ID_down_case = 0x02,
   DW_ID_case_insensitive = 0x03
 };
 

llvm/lib/IR/Verifier.cpp

class Verifier : public InstVisitor<Verifier>, VerifierSupport {
 
   /// Whether we've seen a call to @llvm.localescape in this function
   /// already.
   bool SawFrameEscape;
 
   /// Whether the current function has a DISubprogram attached to it.
   bool HasDebugInfo = false;
 
+  /// The current source language.
+  dwarf::SourceLanguage CurrentSourceLang = dwarf::DW_LANG_lo_user;
+
   /// Whether source was present on the first DIFile encountered in each CU.
   DenseMap<const DICompileUnit *, bool> HasSourceDebugInfo;
 
   /// Stores the count of how many objects were passed to llvm.localescape for a
   /// given function and the largest index passed to llvm.localrecover.
   DenseMap<Function *, std::pair<unsigned, unsigned>> FrameEscapeInfo;
 
   // Maps catchswitches and cleanuppads that unwind to siblings to the

 
 void Verifier::visitDIScope(const DIScope &N) {
   if (auto *F = N.getRawFile())
     AssertDI(isa<DIFile>(F), "invalid file", &N, F);
 }
 
 void Verifier::visitDISubrange(const DISubrange &N) {
   AssertDI(N.getTag() == dwarf::DW_TAG_subrange_type, "invalid tag", &N);
-  AssertDI(N.getRawCountNode() || N.getRawUpperBound(),
+  bool HasAssumedSizedArraySupport = dwarf::isFortran(CurrentSourceLang);
+  AssertDI(HasAssumedSizedArraySupport || N.getRawCountNode() ||
+               N.getRawUpperBound(),
            "Subrange must contain count or upperBound", &N);
   AssertDI(!N.getRawCountNode() || !N.getRawUpperBound(),
            "Subrange can have any one of count or upperBound", &N);
   AssertDI(!N.getRawCountNode() || N.getCount(),
            "Count must either be a signed constant or a DIVariable", &N);
   auto Count = N.getCount();
   AssertDI(!Count || !Count.is<ConstantInt *>() ||
                Count.get<ConstantInt *>()->getSExtValue() >= -1,
            "invalid subrange count", &N);
   auto *LBound = N.getRawLowerBound();
   AssertDI(!LBound || isa<ConstantAsMetadata>(LBound) ||
void Verifier::visitDICompileUnit(const DICompileUnit &N) {
 
   // Don't bother verifying the compilation directory or producer string
   // as those could be empty.
   AssertDI(N.getRawFile() && isa<DIFile>(N.getRawFile()), "invalid file", &N,
            N.getRawFile());
   AssertDI(!N.getFile()->getFilename().empty(), "invalid filename", &N,
            N.getFile());
 
+  CurrentSourceLang = (dwarf::SourceLanguage)N.getSourceLanguage();
+
   verifySourceDebugInfo(N, *N.getFile());
 
   AssertDI((N.getEmissionKind() <= DICompileUnit::LastEmissionKind),
            "invalid emission kind", &N);
 
   if (auto *Array = N.getRawEnumTypes()) {
     AssertDI(isa<MDTuple>(Array), "invalid enum list", &N, Array);
     for (Metadata *Op : N.getEnumTypes()->operands()) {

llvm/test/DebugInfo/X86/assumed_size_array.ll

+;; Check whether fortran assumed size array is accepted
+;; which has upperBound absent in DISubrange
+
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu %s -filetype=obj -o %t.o
+; RUN: llvm-dwarfdump  %t.o | FileCheck %s
+
+; CHECK-LABEL: DW_TAG_formal_parameter
+; CHECK: DW_AT_name    ("array1")
+; CHECK: DW_AT_type    ([[type1:0x[0-9a-f]+]]
+; CHECK-LABEL: DW_TAG_formal_parameter
+; CHECK: DW_AT_name    ("array2")
+; CHECK: DW_AT_type    ([[type2:0x[0-9a-f]+]]
+; CHECK: [[type1]]:   DW_TAG_array_type
+; CHECK: DW_TAG_subrange_type
+; CHECK: [[type2]]:   DW_TAG_array_type
+; CHECK: DW_TAG_subrange_type
+; CHECK: DW_AT_lower_bound     (4)
+; CHECK: DW_AT_upper_bound     (9)
+; CHECK: DW_TAG_subrange_type
+; CHECK: DW_AT_lower_bound     (10)
+;
+;
+;; original fortran program
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;subroutine sub (array1, array2)
+;;  integer :: array1 (*)
+;;  integer :: array2 (4:9, 10:*)
+;;
+;;  array1(7:8) = 9
+;;  array2(5, 10) = 10
+;;end subroutine
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+; ModuleID = 'assumed_size_array.ll'
+source_filename = "assumed_size_array.ll"
+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"
+
+@.C344_sub_ = internal constant i32 10
+@.C345_sub_ = internal constant i64 10
+@.C351_sub_ = internal constant i64 5
+@.C341_sub_ = internal constant i32 9
+@.C322_sub_ = internal constant i64 1
+@.C350_sub_ = internal constant i64 8
+@.C349_sub_ = internal constant i64 7
+
+define void @sub_(i64* noalias %array1, i64* noalias %array2) #0 !dbg !5 {
+L.entry:
+  %.dY0001_361 = alloca i64, align 8
+  %"i$a_357" = alloca i64, align 8
+  call void @llvm.dbg.declare(metadata i64* %array1, metadata !16, metadata !DIExpression()), !dbg !17
+  call void @llvm.dbg.declare(metadata i64* %array2, metadata !18, metadata !DIExpression()), !dbg !17
+  br label %L.LB1_364
+
+L.LB1_364:                                        ; preds = %L.entry
+  store i64 2, i64* %.dY0001_361, align 8, !dbg !19
+  call void @llvm.dbg.declare(metadata i64* %"i$a_357", metadata !20, metadata !DIExpression()), !dbg !17
+  store i64 7, i64* %"i$a_357", align 8, !dbg !19
+  br label %L.LB1_359
+
+L.LB1_359:                                        ; preds = %L.LB1_359, %L.LB1_364
+  %0 = load i64, i64* %"i$a_357", align 8, !dbg !19
+  call void @llvm.dbg.value(metadata i64 %0, metadata !22, metadata !DIExpression()), !dbg !17
+  %1 = bitcast i64* %array1 to i8*, !dbg !19
+  %2 = getelementptr i8, i8* %1, i64 -4, !dbg !19
+  %3 = bitcast i8* %2 to i32*, !dbg !19
+  %4 = getelementptr i32, i32* %3, i64 %0, !dbg !19
+  store i32 9, i32* %4, align 4, !dbg !19
+  %5 = load i64, i64* %"i$a_357", align 8, !dbg !19
+  call void @llvm.dbg.value(metadata i64 %5, metadata !23, metadata !DIExpression()), !dbg !17
+  %6 = add nsw i64 %5, 1, !dbg !19
+  store i64 %6, i64* %"i$a_357", align 8, !dbg !19
+  %7 = load i64, i64* %.dY0001_361, align 8, !dbg !19
+  %8 = sub nsw i64 %7, 1, !dbg !19
+  store i64 %8, i64* %.dY0001_361, align 8, !dbg !19
+  %9 = load i64, i64* %.dY0001_361, align 8, !dbg !19
+  %10 = icmp sgt i64 %9, 0, !dbg !19
+  br i1 %10, label %L.LB1_359, label %L.LB1_383, !dbg !19
+
+L.LB1_383:                                        ; preds = %L.LB1_359
+  %11 = bitcast i64* %array2 to i8*, !dbg !24
+  %12 = getelementptr i8, i8* %11, i64 4, !dbg !24
+  %13 = bitcast i8* %12 to i32*, !dbg !24
+  store i32 10, i32* %13, align 4, !dbg !24
+  ret void, !dbg !25
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.module.flags = !{!0, !1}
+!llvm.dbg.cu = !{!2}
+
+!0 = !{i32 2, !"Dwarf Version", i32 4}
+!1 = !{i32 2, !"Debug Info Version", i32 3}
+!2 = distinct !DICompileUnit(language: DW_LANG_Fortran90, file: !3, producer: " F90 Flang - 1.5 2017-05-01", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, retainedTypes: !4, globals: !4, imports: !4)
+!3 = !DIFile(filename: "assumed_size_array.f90", directory: "/tmp")
+!4 = !{}
+!5 = distinct !DISubprogram(name: "sub", scope: !2, file: !3, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !2)
+!6 = !DISubroutineType(types: !7)
+!7 = !{null, !8, !12}
+!8 = !DICompositeType(tag: DW_TAG_array_type, baseType: !9, align: 32, elements: !10)
+!9 = !DIBasicType(name: "integer", size: 32, align: 32, encoding: DW_ATE_signed)
+!10 = !{!11}
+!11 = !DISubrange(lowerBound: 1)
+!12 = !DICompositeType(tag: DW_TAG_array_type, baseType: !9, align: 32, elements: !13)
+!13 = !{!14, !15}
+!14 = !DISubrange(lowerBound: 4, upperBound: 9)
+!15 = !DISubrange(lowerBound: 10)
+!16 = !DILocalVariable(name: "array1", arg: 1, scope: !5, file: !3, line: 1, type: !8)
+!17 = !DILocation(line: 0, scope: !5)
+!18 = !DILocalVariable(name: "array2", arg: 2, scope: !5, file: !3, line: 1, type: !12)
+!19 = !DILocation(line: 5, column: 1, scope: !5)
+!20 = distinct !DILocalVariable(scope: !5, file: !3, type: !21, flags: DIFlagArtificial)
+!21 = !DIBasicType(name: "integer*8", size: 64, align: 64, encoding: DW_ATE_signed)
+!22 = distinct !DILocalVariable(scope: !5, file: !3, type: !21, flags: DIFlagArtificial)
+!23 = distinct !DILocalVariable(scope: !5, file: !3, type: !21, flags: DIFlagArtificial)
+!24 = !DILocation(line: 6, column: 1, scope: !5)
+!25 = !DILocation(line: 7, column: 1, scope: !5)