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[MC] Fix DWARF file table for files with empty DWARF (#119020) #119229

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Merged
merged 1 commit into from
Dec 10, 2024
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[MC] Fix DWARF file table for files with empty DWARF (#119020) #119229

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25 changes: 15 additions & 10 deletions llvm/lib/MC/MCParser/AsmParser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -162,8 +162,8 @@ class AsmParser : public MCAsmParser {
};
CppHashInfoTy CppHashInfo;

/// The filename from the first cpp hash file line comment, if any.
StringRef FirstCppHashFilename;
/// Have we seen any file line comment.
bool HadCppHashFilename = false;

/// List of forward directional labels for diagnosis at the end.
SmallVector<std::tuple<SMLoc, CppHashInfoTy, MCSymbol *>, 4> DirLabels;
Expand Down Expand Up @@ -952,12 +952,6 @@ bool AsmParser::enabledGenDwarfForAssembly() {
// the assembler source was produced with debug info already) then emit one
// describing the assembler source file itself.
if (getContext().getGenDwarfFileNumber() == 0) {
// Use the first #line directive for this, if any. It's preprocessed, so
// there is no checksum, and of course no source directive.
if (!FirstCppHashFilename.empty())
getContext().setMCLineTableRootFile(
/*CUID=*/0, getContext().getCompilationDir(), FirstCppHashFilename,
/*Cksum=*/std::nullopt, /*Source=*/std::nullopt);
const MCDwarfFile &RootFile =
getContext().getMCDwarfLineTable(/*CUID=*/0).getRootFile();
getContext().setGenDwarfFileNumber(getStreamer().emitDwarfFileDirective(
Expand Down Expand Up @@ -2440,8 +2434,19 @@ bool AsmParser::parseCppHashLineFilenameComment(SMLoc L, bool SaveLocInfo) {
CppHashInfo.Filename = Filename;
CppHashInfo.LineNumber = LineNumber;
CppHashInfo.Buf = CurBuffer;
if (FirstCppHashFilename.empty())
FirstCppHashFilename = Filename;
if (!HadCppHashFilename) {
HadCppHashFilename = true;
// If we haven't encountered any .file directives, then the first #line
// directive describes the "root" file and directory of the compilation
// unit.
if (getContext().getGenDwarfFileNumber() == 0) {
// It's preprocessed, so there is no checksum, and of course no source
// directive.
getContext().setMCLineTableRootFile(
/*CUID=*/0, getContext().getCompilationDir(), Filename,
/*Cksum=*/std::nullopt, /*Source=*/std::nullopt);
}
}
return false;
}

Expand Down
26 changes: 26 additions & 0 deletions llvm/test/MC/ELF/debug-hash-file-empty-dwarf.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
// RUN: llvm-mc -triple x86_64-unknown-linux-gnu -filetype obj -g -dwarf-version 5 -o %t %s
// RUN: llvm-dwarfdump -debug-info -debug-line %t | FileCheck %s

// CHECK-NOT: DW_TAG_

// CHECK: include_directories[ 0] =
// CHECK-NOT: include_directories[ 1] =
// CHECK: file_names[ 0]:
// CHECK-NEXT: name: "/MyTest/Inputs/other.S"
// CHECK-NEXT: dir_index: 0
// CHECK-NOT: file_names[ 1]:

// RUN: llvm-mc -triple=x86_64 -filetype=obj -g -dwarf-version=5 -fdebug-prefix-map=/MyTest=/src_root %s -o %t.5.o
// RUN: llvm-dwarfdump -debug-info -debug-line %t.5.o | FileCheck %s --check-prefixes=MAP

// MAP-NOT: DW_TAG_

// MAP: include_directories[ 0] = "{{.*}}"
// MAP-NEXT: file_names[ 0]:
// MAP-NEXT: name: "/src_root/Inputs/other.S"
// MAP-NEXT: dir_index: 0

# 1 "/MyTest/Inputs/other.S"

.section .data
.asciz "data"
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