Fix compatibility with current MCStreamer Line Label implementation

Author: Alex B

llvm/include/llvm/MC/MCDwarf.h

@@ -123,9 +123,6 @@ class MCDwarfLoc {
   friend class MCContext;
   friend class MCDwarfLineEntry;
 
-  // DwarfDebug::endFunctionImpl needs to construct MCDwarfLoc(IsEndOfFunction)
-  friend class DwarfDebug;
-
   MCDwarfLoc(unsigned fileNum, unsigned line, unsigned column, unsigned flags,
              unsigned isa, unsigned discriminator)
       : FileNum(fileNum), Line(line), Column(column), Flags(flags), Isa(isa),
@@ -242,7 +239,7 @@ class MCLineSection {
 
   // Add an end entry by cloning the last entry, if exists, for the section
   // the given EndLabel belongs to. The label is replaced by the given EndLabel.
-  void addEndEntry(MCSymbol *EndLabel, bool generatingFuncLineTableOffsets);
+  void addEndEntry(MCSymbol *EndLabel);
 
   using MCDwarfLineEntryCollection = std::vector<MCDwarfLineEntry>;
   using iterator = MCDwarfLineEntryCollection::iterator;

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -2262,8 +2262,7 @@ void DwarfDebug::terminateLineTable(const DwarfCompileUnit *CU) {
       getDwarfCompileUnitIDForLineTable(*CU));
   // Add the last range label for the given CU.
   LineTable.getMCLineSections().addEndEntry(
-      const_cast<MCSymbol *>(CURanges.back().End),
-      EmitFuncLineTableOffsetsOption);
+      const_cast<MCSymbol *>(CURanges.back().End));
 }
 
 void DwarfDebug::skippedNonDebugFunction() {
@@ -2356,21 +2355,6 @@ void DwarfDebug::endFunctionImpl(const MachineFunction *MF) {
   // Construct call site entries.
   constructCallSiteEntryDIEs(*SP, TheCU, ScopeDIE, *MF);
 
-  // If we're emitting line table offsets, we also need to emit an end label
-  // after all function's line entries
-  if (EmitFuncLineTableOffsetsOption) {
-    MCSymbol *LineSym = Asm->OutStreamer->getContext().createTempSymbol();
-    Asm->OutStreamer->emitLabel(LineSym);
-    MCDwarfLoc DwarfLoc(
-        1, 1, 0, DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0, 0, 0);
-    MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
-    Asm->OutStreamer->getContext()
-        .getMCDwarfLineTable(
-            Asm->OutStreamer->getContext().getDwarfCompileUnitID())
-        .getMCLineSections()
-        .addLineEntry(LineEntry, Asm->OutStreamer->getCurrentSectionOnly());
-  }
-
   // Clear debug info
   // Ownership of DbgVariables is a bit subtle - ScopeVariables owns all the
   // DbgVariables except those that are also in AbstractVariables (since they

llvm/lib/MC/MCDwarf.cpp

@@ -104,17 +104,22 @@ void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
   // Get the current .loc info saved in the context.
   const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
 
-  MCSymbol *LineStreamLabel = nullptr;
   // If functions need offsets into the generated line table, then we need to
   // create a label referencing where the line was generated in the output
   // stream
-  if (MCOS->getGenerateFuncLineTableOffsets()) {
-    LineStreamLabel = MCOS->getContext().createTempSymbol();
+  if (MCOS->getGenerateFuncLineTableOffsets() &&
+      !MCOS->getCurrentFuncFirstLineStreamSym()) {
+    MCSymbol *LineStreamLabel = MCOS->getContext().createTempSymbol();
     MCOS->emittedLineStreamSym(LineStreamLabel);
+    MCDwarfLineEntry LabelLineEntry(LineSym, DwarfLoc, LineStreamLabel);
+    MCOS->getContext()
+        .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
+        .getMCLineSections()
+        .addLineEntry(LabelLineEntry, Section);
   }
 
   // Create a (local) line entry with the symbol and the current .loc info.
-  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc, LineStreamLabel);
+  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
 
   // clear DwarfLocSeen saying the current .loc info is now used.
   MCOS->getContext().clearDwarfLocSeen();
@@ -154,8 +159,7 @@ makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
   return Res;
 }
 
-void MCLineSection::addEndEntry(MCSymbol *EndLabel,
-                                bool generatingFuncLineTableOffsets) {
+void MCLineSection::addEndEntry(MCSymbol *EndLabel) {
   auto *Sec = &EndLabel->getSection();
   // The line table may be empty, which we should skip adding an end entry.
   // There are two cases:
@@ -168,12 +172,8 @@ void MCLineSection::addEndEntry(MCSymbol *EndLabel,
   if (I != MCLineDivisions.end()) {
     auto &Entries = I->second;
     auto EndEntry = Entries.back();
-    // If generatingFuncLineTableOffsets is set, then we already generated an
-    // end label at the end of the last function, so skip generating another one
-    if (!generatingFuncLineTableOffsets) {
-      EndEntry.setEndLabel(EndLabel);
-      Entries.push_back(EndEntry);
-    }
+    EndEntry.setEndLabel(EndLabel);
+    Entries.push_back(EndEntry);
   }
 }
 

llvm/test/DebugInfo/X86/DW_AT_LLVM_stmt_seq_sec_offset.ll

@@ -12,20 +12,20 @@
 ; STMT_SEQ:       DW_AT_LLVM_stmt_sequence [DW_FORM_sec_offset]	(0x00000028)
 ; STMT_SEQ:   DW_AT_name {{.*}}func01
 ; STMT_SEQ:   DW_TAG_subprogram [[[ABBREV_CODE]]]
-; STMT_SEQ:       DW_AT_LLVM_stmt_sequence [DW_FORM_sec_offset]	(0x00000033)
+; STMT_SEQ:       DW_AT_LLVM_stmt_sequence [DW_FORM_sec_offset]	(0x00000036)
 ; STMT_SEQ:   DW_AT_name {{.*}}main
 
 ;; Check that the line table starts at 0x00000028 (first function)
 ; STMT_SEQ:            Address            Line   Column File   ISA Discriminator OpIndex Flags
 ; STMT_SEQ-NEXT:       ------------------ ------ ------ ------ --- ------------- ------- -------------
-; STMT_SEQ-NEXT:  0x00000028: 00 DW_LNE_set_address (0x00000006)
+; STMT_SEQ-NEXT:  0x00000028: 05 DW_LNS_set_column (3)
 
-;; Check that we have an 'end_sequence' just before the next function (0x00000033)
-; STMT_SEQ:            0x0000000000000006      1      0      1   0             0       0  is_stmt end_sequence
-; STMT_SEQ-NEXT: 0x00000033: 00 DW_LNE_set_address (0x00000027)
+;; Check that we have an 'end_sequence' just before the next function (0x00000036)
+; STMT_SEQ:            0x0000000000000000      2      3      1   0             0       0  is_stmt end_sequence
+; STMT_SEQ-NEXT: 0x00000036: 00 DW_LNE_set_address (0x00000010)
 
 ;; Check that the end of the line table still has an 'end_sequence'
-; STMT_SEQ       0x00000049: 00 DW_LNE_end_sequence
+; STMT_SEQ       0x00000047: 00 DW_LNE_end_sequence
 ; STMT_SEQ-NEXT        0x0000000000000027      6      3      1   0             0       0  end_sequence