[AsmPrinter] fix -disable-debug-info option

[vtjnash]

Summary

This option was in a rather convoluted place, causing global parameters
to be set in awkward and undesirable ways to try to account for it
indirectly. Add tests for the -disable-debug-info option and ensure we
don't print unintended markers from unintended places.

[uabelho]

Thanks! The problem I saw is fixed with this patch.

@dstenb : Any opinions about this?

[dstenb]

Thanks! This looks good to me.

Since the option is now moved into AsmPrinter, can you add a FIXME comment to clarify that the option does (still) not work when emitting CodeView? E.g. at line 320.

[hans]

The test fails on Mac, see e.g. https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8863756117615904432/+/steps/package_clang/0/stdout

The output of the first run line is:

$ bin/llc -disable-debug-info-print=true -exception-model=dwarf -o - ../llvm/test/CodeGen/Generic/disable-debug-info-print.ll
        .section        __TEXT,__text,regular,pure_instructions
        .build_version macos, 10, 15
        .globl  _main                           ## -- Begin function main
        .p2align        4, 0x90
_main:                                  ## @main
## %bb.0:                               ## %entry
        xorl    %eax, %eax
        retq
                                        ## -- End function
        .globl  _helper                         ## -- Begin function helper
        .p2align        4, 0x90
_helper:                                ## @helper
        .cfi_startproc
## %bb.0:                               ## %entry
        xorl    %eax, %eax
        retq
        .cfi_endproc
                                        ## -- End function
.subsections_via_symbols

Note that the .file directive which the test checks for isn't there.

The failure is probably reproducible by passing a -mtriple=darwin something to llc.

I've reverted in 105ed27ed80dd47a9d32e72bbdd2a776a3318f38 in the meantime.

[vtjnash]

Thanks for identifying that. I think I can re-land just without that part of the test. It is not essential, I added it just to try to check all of the dwarf-related output.

[hans]

In D91083#2395780, @vtjnash wrote:

Thanks for identifying that. I think I can re-land just without that part of the test. It is not essential, I added it just to try to check all of the dwarf-related output.

Sounds good to me, as long as it passes :)

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

 #include <string>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "asm-printer"
 
+// FIXME: this option currently only applies to DWARF, and not CodeView, tables
+static cl::opt<bool>
+    DisableDebugInfoPrinting("disable-debug-info-print", cl::Hidden,
+                             cl::desc("Disable debug info printing"));
+
 static const char *const DWARFGroupName = "dwarf";
 static const char *const DWARFGroupDescription = "DWARF Emission";
 static const char *const DbgTimerName = "emit";
 static const char *const DbgTimerDescription = "Debug Info Emission";
 static const char *const EHTimerName = "write_exception";
 static const char *const EHTimerDescription = "DWARF Exception Writer";
 static const char *const CFGuardName = "Control Flow Guard";
 static const char *const CFGuardDescription = "Control Flow Guard";
const MCSubtargetInfo &AsmPrinter::getSubtargetInfo() const {
   return MF->getSubtarget<MCSubtargetInfo>();
 }
 
 void AsmPrinter::EmitToStreamer(MCStreamer &S, const MCInst &Inst) {
   S.emitInstruction(Inst, getSubtargetInfo());
 }
 
 void AsmPrinter::emitInitialRawDwarfLocDirective(const MachineFunction &MF) {
-  assert(DD && "Dwarf debug file is not defined.");
-  assert(OutStreamer->hasRawTextSupport() && "Expected assembly output mode.");
+  if (DD) {
+    assert(OutStreamer->hasRawTextSupport() &&
+           "Expected assembly output mode.");
     (void)DD->emitInitialLocDirective(MF, /*CUID=*/0);
   }
+}
 
 /// getCurrentSection() - Return the current section we are emitting to.
 const MCSection *AsmPrinter::getCurrentSection() const {
   return OutStreamer->getCurrentSectionOnly();
 }
 
 void AsmPrinter::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
bool AsmPrinter::doInitialization(Module &M) {
   const_cast<TargetLoweringObjectFile&>(getObjFileLowering())
     .Initialize(OutContext, TM);
 
   const_cast<TargetLoweringObjectFile &>(getObjFileLowering())
       .getModuleMetadata(M);
 
   OutStreamer->InitSections(false);
 
+  if (DisableDebugInfoPrinting)
+    MMI->setDebugInfoAvailability(false);
+
   // Emit the version-min deployment target directive if needed.
   //
   // FIXME: If we end up with a collection of these sorts of Darwin-specific
   // or ELF-specific things, it may make sense to have a platform helper class
   // that will work with the target helper class. For now keep it here, as the
   // alternative is duplicated code in each of the target asm printers that
   // use the directive, where it would need the same conditionalization
   // anyway.
if (MAI->doesSupportDebugInformation()) {
     bool EmitCodeView = M.getCodeViewFlag();
     if (EmitCodeView && TM.getTargetTriple().isOSWindows()) {
       Handlers.emplace_back(std::make_unique<CodeViewDebug>(this),
                             DbgTimerName, DbgTimerDescription,
                             CodeViewLineTablesGroupName,
                             CodeViewLineTablesGroupDescription);
     }
     if (!EmitCodeView || M.getDwarfVersion()) {
+      if (!DisableDebugInfoPrinting) {
         DD = new DwarfDebug(this);
         Handlers.emplace_back(std::unique_ptr<DwarfDebug>(DD), DbgTimerName,
                               DbgTimerDescription, DWARFGroupName,
                               DWARFGroupDescription);
       }
     }
+  }
 
   switch (MAI->getExceptionHandlingType()) {
   case ExceptionHandling::SjLj:
   case ExceptionHandling::DwarfCFI:
   case ExceptionHandling::ARM:
     isCFIMoveForDebugging = true;
     if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
       break;

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

 #include <string>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "dwarfdebug"
 
 STATISTIC(NumCSParams, "Number of dbg call site params created");
 
-static cl::opt<bool>
-DisableDebugInfoPrinting("disable-debug-info-print", cl::Hidden,
-                         cl::desc("Disable debug info printing"));
-
 static cl::opt<bool> UseDwarfRangesBaseAddressSpecifier(
     "use-dwarf-ranges-base-address-specifier", cl::Hidden,
     cl::desc("Use base address specifiers in debug_ranges"), cl::init(false));
 
 static cl::opt<bool> GenerateARangeSection("generate-arange-section",
                                            cl::Hidden,
                                            cl::desc("Generate dwarf aranges"),
                                            cl::init(false));

 }
 
 // Emit all Dwarf sections that should come prior to the content. Create
 // global DIEs and emit initial debug info sections. This is invoked by
 // the target AsmPrinter.
 void DwarfDebug::beginModule(Module *M) {
   DebugHandlerBase::beginModule(M);
 
-  if (!Asm || !MMI->hasDebugInfo() || DisableDebugInfoPrinting)
+  if (!Asm || !MMI->hasDebugInfo())
     return;
 
   unsigned NumDebugCUs = std::distance(M->debug_compile_units_begin(),
                                        M->debug_compile_units_end());
   assert(NumDebugCUs > 0 && "Asm unexpectedly initialized");
   assert(MMI->hasDebugInfo() &&
          "DebugInfoAvailabilty unexpectedly not initialized");
   SingleCU = NumDebugCUs == 1;
void DwarfDebug::endModule() {
   assert(CurMI == nullptr);
 
   for (const auto &P : CUMap) {
     auto &CU = *P.second;
     CU.createBaseTypeDIEs();
   }
 
   // If we aren't actually generating debug info (check beginModule -
-  // conditionalized on !DisableDebugInfoPrinting and the presence of the
-  // llvm.dbg.cu metadata node)
-  if (!Asm || !MMI->hasDebugInfo() || DisableDebugInfoPrinting)
+  // conditionalized on the presence of the llvm.dbg.cu metadata node)
+  if (!Asm || !MMI->hasDebugInfo())
     return;
 
   // Finalize the debug info for the module.
   finalizeModuleInfo();
 
   if (useSplitDwarf())
     // Emit debug_loc.dwo/debug_loclists.dwo section.
     emitDebugLocDWO();

llvm/test/CodeGen/Generic/disable-debug-info-print.ll

+; RUN: llc -disable-debug-info-print=true -exception-model=dwarf -o - %s | FileCheck %s
+; RUN: llc -disable-debug-info-print=true -exception-model=sjlj -o - %s | FileCheck %s --check-prefix=SJLJ-CHECK
+
+define i16 @main() nounwind !dbg !7 {
+entry:
+  ret i16 0, !dbg !9
+}
+
+define i16 @helper() !dbg !10 {
+entry:
+  ret i16 0, !dbg !11
+}
+
+
+; CHECK: .file   "disable-debug-info-print.ll"
+; CHECK: main
+; CHECK-NOT: cfi_startproc
+; CHECK-NOT: .file
+; CHECK-NOT: .loc
+; CHECK: helper
+; CHECK: cfi_startproc
+; CHECK-NOT: .file
+; CHECK-NOT: .loc
+; CHECK: cfi_endproc
+
+; SJLJ-CHECK: .file   "disable-debug-info-print.ll"
+; SJLJ-CHECK: main
+; SJLJ-CHECK-NOT: cfi_startproc
+; SJLJ-CHECK-NOT: .file
+; SJLJ-CHECK-NOT: .loc
+; SJLJ-CHECK: helper
+; SJLJ-CHECK-NOT: cfi_startproc
+; SJLJ-CHECK-NOT: .file
+; SJLJ-CHECK-NOT: .loc
+
+
+!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 12.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "unwind-tables.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 7, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 12.0.0"}
+!7 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !2)
+!9 = !DILocation(line: 2, column: 3, scope: !7)
+!10 = distinct !DISubprogram(name: "helper", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!11 = !DILocation(line: 2, column: 3, scope: !10)