[DEBUGINFO, NVPTX] Removed Label Arithmetic from DWARF Pub Sections for NVPTX

[jdtatz]

Summary

The NVPTX target disallows both labels in debug sections and label arithmetic,
so instead the content sizes are computed before writing. The new test
in "debug-pub.ll" was added for this specfic change. Also included
are the renabling of Data16bitsDirective and NVPTXTargetStreamer::emitRawBytes,
which have been fixed since CUDA 9.0, with the debuginfo tests updated for this.

[jdtatz]

Removed the renabling of Data16bitsDirective and NVPTXTargetStreamer::emitRawBytes as it's
extraneous to the point of this patch and should be submitted in a new patch afterwards.

[ABataev]

If I do recall it correctly, NVPTX debug info does not support pub sections. You just need to tweak the frontend to disable emission of pub sections (need to add , nameTableKind: None to the DICompileUnit)

[jdtatz]

In D88196#2292440, @ABataev wrote:

If I do recall it correctly, NVPTX debug info does not support pub sections. You just need to tweak the frontend to disable emission of pub sections (need to add , nameTableKind: None to the DICompileUnit)

Sorry that I took so long to respond.
But I was able to find information on which dwarf sections ptx supports in the official documentation.
https://docs.nvidia.com/cuda/ptx-writers-guide-to-interoperability/index.html#debug-information
They also mention that they support the "debug_aranges" section which is currently disabled for only the NVPTX backend, but I could re-enable it if that's ok.

[jdtatz]

Updated LLVM.DebugInfo/X86::dwarf-pubnames-split.ll test to remove the label arithmetic
Fixed my new test where I forgot to include the new lengths in the last update
Although I don't understand yet, why LLVM.DebugInfo/X86::debug-pubtables-dwarf64.ll is failing.

[ABataev]

In D88196#2310275, @jdtatz wrote:

In D88196#2292440, @ABataev wrote:

If I do recall it correctly, NVPTX debug info does not support pub sections. You just need to tweak the frontend to disable emission of pub sections (need to add , nameTableKind: None to the DICompileUnit)

Sorry that I took so long to respond.
But I was able to find information on which dwarf sections ptx supports in the official documentation.
https://docs.nvidia.com/cuda/ptx-writers-guide-to-interoperability/index.html#debug-information
They also mention that they support the "debug_aranges" section which is currently disabled for only the NVPTX backend, but I could re-enable it if that's ok.

Yeah, they are just optional.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

2338–2356

I would guard this with the check for DwarfSectionsAsReferences flag.

[jdtatz]

Used @ABataev suggestion of adding a "guard this with the check for DwarfSectionsAsReferences",
so that these changes are only used for targets that don't support labels in Dwarf sections.

[ABataev]

Did you check if ptxas can process it correctly? Are there any problems with it? I did not see that nvcc generates these sections at all.

[jdtatz]

In D88196#2314796, @ABataev wrote:

Did you check if ptxas can process it correctly? Are there any problems with it? I did not see that nvcc generates these sections at all.

It can and you can check with ptxas $PTX_FILE -o $OUT && llvm-dwarfdump $OUT -debug-pubnames
To get nvcc to generate it you can use the example in their ptx interop guide, but you must pass the --device-debug / -G flag to nvcc for it to generate the "debug_pubnames" section.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

 }
 
 void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
                                      DwarfCompileUnit *TheU,
                                      const StringMap<const DIE *> &Globals) {
   if (auto *Skeleton = TheU->getSkeleton())
     TheU = Skeleton;
 
+  unsigned OffsetByteSize = Asm->getDwarfOffsetByteSize();
+  unsigned UnitLengthFieldByteSize = Asm->getUnitLengthFieldByteSize();
+  // Emit size of content not including length itself.
+  unsigned ContentSize = sizeof(int16_t) + // DWARF version number
+                         OffsetByteSize +  // Offset of CU in the .debug_info
+                                           // section
+                         UnitLengthFieldByteSize + // Compilation Unit Length
+                         Globals.size() * OffsetByteSize + // DIE Offsets
+                         OffsetByteSize;                   // End Mark
+  for (const auto &GI : Globals) {
+    // External Name string + null terminator
+    ContentSize += GI.getKeyLength() + 1;
+  }
+  if (GnuStyle) {
+    // GNU Attributes
+    ContentSize += Globals.size() * sizeof(int8_t);
+  }
   // Emit the header.
-  MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + Name + "_begin");
-  MCSymbol *EndLabel = Asm->createTempSymbol("pub" + Name + "_end");
-  Asm->emitDwarfUnitLength(EndLabel, BeginLabel,
-                           "Length of Public " + Name + " Info");
-
-  Asm->OutStreamer->emitLabel(BeginLabel);
+  Asm->emitDwarfUnitLength(ContentSize, "Length of Public " + Name + " Info");
 
   Asm->OutStreamer->AddComment("DWARF Version");
   Asm->emitInt16(dwarf::DW_PUBNAMES_VERSION);
 
   Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
   emitSectionReference(*TheU);
 
   Asm->OutStreamer->AddComment("Compilation Unit Length");
for (const auto &GI : Globals) {
     }
 
     Asm->OutStreamer->AddComment("External Name");
     Asm->OutStreamer->emitBytes(StringRef(Name, GI.getKeyLength() + 1));
   }
 
   Asm->OutStreamer->AddComment("End Mark");
   Asm->emitDwarfLengthOrOffset(0);
-  Asm->OutStreamer->emitLabel(EndLabel);
 }
 
 /// Emit null-terminated strings into a debug str section.
 void DwarfDebug::emitDebugStr() {
   MCSection *StringOffsetsSection = nullptr;
   if (useSegmentedStringOffsetsTable()) {
     emitStringOffsetsTableHeader();
     StringOffsetsSection = Asm->getObjFileLowering().getDwarfStrOffSection();

llvm/test/DebugInfo/NVPTX/debug-pub.ll

+; RUN: llc -mtriple=nvptx64-nvidia-cuda < %s | FileCheck %s
+
+define ptx_kernel void @kernel() !dbg !5 {
+start:
+  br label %bb1
+
+bb1:
+  br label %bb1
+}
+
+!llvm.module.flags = !{!0, !1}
+!llvm.dbg.cu = !{!2}
+
+!0 = !{i32 7, !"PIC Level", i32 2}
+!1 = !{i32 2, !"Debug Info Version", i32 3}
+!2 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !3, producer: "clang LLVM (rustc version 1.48.0-nightly (99111606f 2020-09-11))", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4)
+!3 = !DIFile(filename: "lib.rs", directory: "")
+!4 = !{}
+!5 = distinct !DISubprogram(name: "kernel", scope: !7, file: !6, line: 10, type: !8, scopeLine: 10, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, templateParams: !4, retainedNodes: !4)
+!6 = !DIFile(filename: "lib.rs", directory: "", checksumkind: CSK_MD5, checksum: "5c76434cae4ba8670c6cce70da6b7d0e")
+!7 = !DINamespace(name: "", scope: null)
+!8 = !DISubroutineType(types: !4)
+!9 = !DILocation(line: 11, column: 5, scope: !5)
+
+; CHECK:  .file 1 "lib.rs"
+
+; CHECK:  .section  .debug_abbrev
+; CHECK-NEXT:   {
+; CHECK-NEXT:.b8 1                                   // Abbreviation Code
+; CHECK-NEXT:.b8 17                                  // DW_TAG_compile_unit
+; CHECK-NEXT:.b8 1                                   // DW_CHILDREN_yes
+; CHECK-NEXT:.b8 37                                  // DW_AT_producer
+; CHECK-NEXT:.b8 8                                   // DW_FORM_string
+; CHECK-NEXT:.b8 19                                  // DW_AT_language
+; CHECK-NEXT:.b8 5                                   // DW_FORM_data2
+; CHECK-NEXT:.b8 3                                   // DW_AT_name
+; CHECK-NEXT:.b8 8                                   // DW_FORM_string
+; CHECK-NEXT:.b8 16                                  // DW_AT_stmt_list
+; CHECK-NEXT:.b8 6                                   // DW_FORM_data4
+; CHECK-NEXT:.b8 180                                 // DW_AT_GNU_pubnames
+; CHECK-NEXT:.b8 66
+; CHECK-NEXT:.b8 12                                  // DW_FORM_flag
+; CHECK-NEXT:.b8 17                                  // DW_AT_low_pc
+; CHECK-NEXT:.b8 1                                   // DW_FORM_addr
+; CHECK-NEXT:.b8 18                                  // DW_AT_high_pc
+; CHECK-NEXT:.b8 1                                   // DW_FORM_addr
+; CHECK-NEXT:.b8 0                                   // EOM(1)
+; CHECK-NEXT:.b8 0                                   // EOM(2)
+; CHECK-NEXT:.b8 2                                   // Abbreviation Code
+; CHECK-NEXT:.b8 57                                  // DW_TAG_namespace
+; CHECK-NEXT:.b8 1                                   // DW_CHILDREN_yes
+; CHECK-NEXT:.b8 0                                   // EOM(1)
+; CHECK-NEXT:.b8 0                                   // EOM(2)
+; CHECK-NEXT:.b8 3                                   // Abbreviation Code
+; CHECK-NEXT:.b8 46                                  // DW_TAG_subprogram
+; CHECK-NEXT:.b8 0                                   // DW_CHILDREN_no
+; CHECK-NEXT:.b8 17                                  // DW_AT_low_pc
+; CHECK-NEXT:.b8 1                                   // DW_FORM_addr
+; CHECK-NEXT:.b8 18                                  // DW_AT_high_pc
+; CHECK-NEXT:.b8 1                                   // DW_FORM_addr
+; CHECK-NEXT:.b8 64                                  // DW_AT_frame_base
+; CHECK-NEXT:.b8 10                                  // DW_FORM_block1
+; CHECK-NEXT:.b8 3                                   // DW_AT_name
+; CHECK-NEXT:.b8 8                                   // DW_FORM_string
+; CHECK-NEXT:.b8 58                                  // DW_AT_decl_file
+; CHECK-NEXT:.b8 11                                  // DW_FORM_data1
+; CHECK-NEXT:.b8 59                                  // DW_AT_decl_line
+; CHECK-NEXT:.b8 11                                  // DW_FORM_data1
+; CHECK-NEXT:.b8 63                                  // DW_AT_external
+; CHECK-NEXT:.b8 12                                  // DW_FORM_flag
+; CHECK-NEXT:.b8 0                                   // EOM(1)
+; CHECK-NEXT:.b8 0                                   // EOM(2)
+; CHECK-NEXT:.b8 0                                   // EOM(3)
+; CHECK-NEXT: }
+; CHECK-NEXT: .section  .debug_info
+; CHECK-NEXT: {
+; CHECK-NEXT:.b32 135                                // Length of Unit
+; CHECK-NEXT:.b8 2                                   // DWARF version number
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 .debug_abbrev                      // Offset Into Abbrev. Section
+; CHECK-NEXT:.b8 8                                   // Address Size (in bytes)
+; CHECK-NEXT:.b8 1                                   // Abbrev [1] 0xb:0x80 DW_TAG_compile_unit
+; CHECK-NEXT:.b8 99                                  // DW_AT_producer
+; CHECK-NEXT:.b8 108
+; CHECK-NEXT:.b8 97
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 103
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 76
+; CHECK-NEXT:.b8 76
+; CHECK-NEXT:.b8 86
+; CHECK-NEXT:.b8 77
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 40
+; CHECK-NEXT:.b8 114
+; CHECK-NEXT:.b8 117
+; CHECK-NEXT:.b8 115
+; CHECK-NEXT:.b8 116
+; CHECK-NEXT:.b8 99
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 118
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 114
+; CHECK-NEXT:.b8 115
+; CHECK-NEXT:.b8 105
+; CHECK-NEXT:.b8 111
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 46
+; CHECK-NEXT:.b8 52
+; CHECK-NEXT:.b8 56
+; CHECK-NEXT:.b8 46
+; CHECK-NEXT:.b8 48
+; CHECK-NEXT:.b8 45
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 105
+; CHECK-NEXT:.b8 103
+; CHECK-NEXT:.b8 104
+; CHECK-NEXT:.b8 116
+; CHECK-NEXT:.b8 108
+; CHECK-NEXT:.b8 121
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 40
+; CHECK-NEXT:.b8 57
+; CHECK-NEXT:.b8 57
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 54
+; CHECK-NEXT:.b8 48
+; CHECK-NEXT:.b8 54
+; CHECK-NEXT:.b8 102
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 50
+; CHECK-NEXT:.b8 48
+; CHECK-NEXT:.b8 50
+; CHECK-NEXT:.b8 48
+; CHECK-NEXT:.b8 45
+; CHECK-NEXT:.b8 48
+; CHECK-NEXT:.b8 57
+; CHECK-NEXT:.b8 45
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 49
+; CHECK-NEXT:.b8 41
+; CHECK-NEXT:.b8 41
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b8 28                                  // DW_AT_language
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b8 108                                 // DW_AT_name
+; CHECK-NEXT:.b8 105
+; CHECK-NEXT:.b8 98
+; CHECK-NEXT:.b8 46
+; CHECK-NEXT:.b8 114
+; CHECK-NEXT:.b8 115
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 .debug_line                        // DW_AT_stmt_list
+; CHECK-NEXT:.b8 1                                   // DW_AT_GNU_pubnames
+; CHECK-NEXT:.b64 Lfunc_begin0                       // DW_AT_low_pc
+; CHECK-NEXT:.b64 Lfunc_end0                         // DW_AT_high_pc
+; CHECK-NEXT:.b8 2                                   // Abbrev [2] 0x6b:0x1f DW_TAG_namespace
+; CHECK-NEXT:.b8 3                                   // Abbrev [3] 0x6c:0x1d DW_TAG_subprogram
+; CHECK-NEXT:.b64 Lfunc_begin0                       // DW_AT_low_pc
+; CHECK-NEXT:.b64 Lfunc_end0                         // DW_AT_high_pc
+; CHECK-NEXT:.b8 1                                   // DW_AT_frame_base
+; CHECK-NEXT:.b8 156
+; CHECK-NEXT:.b8 107                                 // DW_AT_name
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 114
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 108
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT:.b8 10                                  // DW_AT_decl_line
+; CHECK-NEXT:.b8 1                                   // DW_AT_external
+; CHECK-NEXT:.b8 0                                   // End Of Children Mark
+; CHECK-NEXT:.b8 0                                   // End Of Children Mark
+; CHECK-NEXT: }
+; CHECK-NEXT: .section  .debug_pubnames
+; CHECK-NEXT: {
+; CHECK-NEXT:.b32 47                                 // Length of Public Names Info
+; CHECK-NEXT:.b8 2                                   // DWARF Version
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 .debug_info                        // Offset of Compilation Unit Info
+; CHECK-NEXT:.b32 139                                // Compilation Unit Length
+; CHECK-NEXT:.b32 108                                // DIE offset
+; CHECK-NEXT:.b8 107                                 // External Name
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 114
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 108
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 107                                // DIE offset
+; CHECK-NEXT:.b8 40                                  // External Name
+; CHECK-NEXT:.b8 97
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 111
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 121
+; CHECK-NEXT:.b8 109
+; CHECK-NEXT:.b8 111
+; CHECK-NEXT:.b8 117
+; CHECK-NEXT:.b8 115
+; CHECK-NEXT:.b8 32
+; CHECK-NEXT:.b8 110
+; CHECK-NEXT:.b8 97
+; CHECK-NEXT:.b8 109
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 115
+; CHECK-NEXT:.b8 112
+; CHECK-NEXT:.b8 97
+; CHECK-NEXT:.b8 99
+; CHECK-NEXT:.b8 101
+; CHECK-NEXT:.b8 41
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 0                                  // End Mark
+; CHECK-NEXT: }
+; CHECK-NEXT: .section  .debug_pubtypes
+; CHECK-NEXT: {
+; CHECK-NEXT:.b32 10                                 // Length of Public Types Info
+; CHECK-NEXT:.b8 2                                   // DWARF Version
+; CHECK-NEXT:.b8 0
+; CHECK-NEXT:.b32 .debug_info                        // Offset of Compilation Unit Info
+; CHECK-NEXT:.b32 139                                // Compilation Unit Length
+; CHECK-NEXT:.b32 0                                  // End Mark
+; CHECK-NEXT: }
+; CHECK-NEXT: .section  .debug_loc  { }