Address Feedback Nr.1

Author: Alex B

llvm/include/llvm/MC/MCDwarf.h

@@ -195,8 +195,10 @@ class MCDwarfLineEntry : public MCDwarfLoc {
 public:
   // Constructor to create an MCDwarfLineEntry given a symbol and the dwarf loc.
   MCDwarfLineEntry(MCSymbol *label, const MCDwarfLoc loc,
-                   MCSymbol *lineStreamLabel = nullptr)
-      : MCDwarfLoc(loc), Label(label), LineStreamLabel(lineStreamLabel) {}
+                   MCSymbol *lineStreamLabel = nullptr,
+                   SMLoc streamLabelDefLoc = {})
+      : MCDwarfLoc(loc), Label(label), LineStreamLabel(lineStreamLabel),
+        StreamLabelDefLoc(streamLabelDefLoc) {}
 
   MCSymbol *getLabel() const { return Label; }
 
@@ -205,6 +207,10 @@ class MCDwarfLineEntry : public MCDwarfLoc {
   // line sequence.
   MCSymbol *LineStreamLabel;
 
+  // Location where LineStreamLabel was defined. If there is an error emitting
+  // LineStreamLabel, we can use the SMLoc to report an error.
+  SMLoc StreamLabelDefLoc;
+
   // This indicates the line entry is synthesized for an end entry.
   bool IsEndEntry = false;
 
@@ -371,6 +377,9 @@ class MCDwarfLineTable {
   emitOne(MCStreamer *MCOS, MCSection *Section,
           const MCLineSection::MCDwarfLineEntryCollection &LineEntries);
 
+  void endCurrentSeqAndEmitLineStreamLabel(MCStreamer *MCOS, SMLoc DefLoc,
+                                           StringRef Name);
+
   Expected<unsigned> tryGetFile(StringRef &Directory, StringRef &FileName,
                                 std::optional<MD5::MD5Result> Checksum,
                                 std::optional<StringRef> Source,

llvm/lib/MC/MCDwarf.cpp

@@ -197,7 +197,7 @@ void MCDwarfLineTable::emitOne(
         MCOS->emitDwarfLineEndEntry(Section, LastLabel);
         init();
       }
-      MCOS->emitLabel(LineEntry.LineStreamLabel);
+      MCOS->emitLabel(LineEntry.LineStreamLabel, LineEntry.StreamLabelDefLoc);
 
       IsAtStartSeq = true;
       continue;
@@ -270,6 +270,23 @@ void MCDwarfLineTable::emitOne(
     MCOS->emitDwarfLineEndEntry(Section, LastLabel);
 }
 
+void MCDwarfLineTable::endCurrentSeqAndEmitLineStreamLabel(MCStreamer *MCOS,
+                                                           SMLoc DefLoc,
+                                                           StringRef Name) {
+  auto &ctx = MCOS->getContext();
+  auto *LineStreamLabel = ctx.getOrCreateSymbol(Name);
+  auto *LineSym = ctx.createTempSymbol();
+  const MCDwarfLoc &DwarfLoc = ctx.getCurrentDwarfLoc();
+
+  // Create a 'fake' line entry by having LineStreamLabel be non-null. This
+  // won't actually emit any line information, it will reset the line table
+  // sequence and emit a label at the start of the new line table sequence.
+  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc, LineStreamLabel, DefLoc);
+
+  // Add the line entry to this section's entries.
+  getMCLineSections().addLineEntry(LineEntry, MCOS->getCurrentSectionOnly());
+}
+
 //
 // This emits the Dwarf file and the line tables.
 //

llvm/lib/MC/MCStreamer.cpp

@@ -268,22 +268,9 @@ void MCStreamer::emitDwarfLocDirective(unsigned FileNo, unsigned Line,
 }
 
 void MCStreamer::emitDwarfLocLabelDirective(SMLoc Loc, StringRef Name) {
-  auto &ctx = getContext();
-
-  auto *LineStreamLabel = ctx.getOrCreateSymbol(Name);
-
-  auto *LineSym = ctx.createTempSymbol();
-  const MCDwarfLoc &DwarfLoc = ctx.getCurrentDwarfLoc();
-
-  // Create a 'fake' line entry by having LineStreamLabel be non-null. This
-  // won't actually emit any line information, it will reset the line table
-  // sequence and emit a label at the start of the new line table sequence.
-  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc, LineStreamLabel);
-
-  // Add the line entry to this section's entries.
-  ctx.getMCDwarfLineTable(ctx.getDwarfCompileUnitID())
-      .getMCLineSections()
-      .addLineEntry(LineEntry, getCurrentSectionOnly());
+  getContext()
+      .getMCDwarfLineTable(getContext().getDwarfCompileUnitID())
+      .endCurrentSeqAndEmitLineStreamLabel(this, Loc, Name);
 }
 
 MCSymbol *MCStreamer::getDwarfLineTableSymbol(unsigned CUID) {

llvm/test/MC/ELF/debug-loc-label.s

@@ -2,15 +2,10 @@
 // the requested label at the correct position in the line stream
 
 // RUN: llvm-mc -filetype obj -triple x86_64-linux-elf %s -o %t.o
-// RUN: llvm-objdump -d %t.o | FileCheck %s --check-prefix=CHECK-ASM
 // RUN: llvm-dwarfdump -v --debug-line %t.o | FileCheck %s --check-prefix=CHECK-LINE-TABLE
+// RUN: llvm-objdump -s -j .offset_02 -j .offset_03 -j .offset_05 %t.o | FileCheck %s --check-prefix=CHECK-SECTIONS
+
 
-# CHECK-ASM:        <foo>:
-# CHECK-ASM-NEXT:     movq    %rdx, 0x33
-# CHECK-ASM-NEXT:     movq    %rax, 0x3b
-# CHECK-ASM-NEXT:     movq    %rbx, 0x4e
-# CHECK-ASM-NEXT:     movq    %rcx, 0x60
-# CHECK-ASM-NEXT:     retq
 
 # CHECK-LINE-TABLE:                  Address            Line   Column File   ISA Discriminator OpIndex Flags
 # CHECK-LINE-TABLE-NEXT:             ------------------ ------ ------ ------ --- ------------- ------- -------------
@@ -45,6 +40,15 @@
 # CHECK-LINE-TABLE-NEXT: 0x00000071: 02 DW_LNS_advance_pc (addr += 9, op-index += 0)
 # CHECK-LINE-TABLE-NEXT: 0x00000073: 00 DW_LNE_end_sequence
 # CHECK-LINE-TABLE-NEXT:             0x0000000000000021      1      5      1   0             0       0  is_stmt end_sequence
+
+# CHECK-SECTIONS: Contents of section .offset_02:
+# CHECK-SECTIONS-NEXT: 0000 3b000000
+
+# CHECK-SECTIONS: Contents of section .offset_03:
+# CHECK-SECTIONS-NEXT: 0000 4e000000
+
+# CHECK-SECTIONS: Contents of section .offset_05:
+# CHECK-SECTIONS-NEXT: 0000 60000000
 	.text
 	.file	"test.c"
 	.globl	foo
@@ -55,20 +59,29 @@ foo:
 	.file	1 "test.c"
 	.cfi_startproc
 	.loc	1 1 1
-	mov     %rdx, 0x33
+	mov     %rax, 0x01
 	.loc_label my_label_02
 	.loc	1 1 2
-  movq    %rax, my_label_02-.Lline_table_start0
+	mov     %rax, 0x02
 	.loc	1 1 3
 	.loc_label my_label_03
 	.loc_label my_label_03.1
-  movq    %rbx, my_label_03-.Lline_table_start0
+	mov     %rax, 0x03
 	.loc	1 1 4
-	.loc_label my_label_05
+	.loc_label my_label_04
 	.loc	1 1 5
-  movq    %rcx, my_label_05-.Lline_table_start0
+	mov     %rax, 0x04
 	ret
 	.cfi_endproc
 
 	.section	.debug_line,"",@progbits
 .Lline_table_start0:
+
+	.section	.offset_02,"",@progbits
+	.quad	my_label_02-.Lline_table_start0
+
+	.section	.offset_03,"",@progbits
+	.quad	my_label_03-.Lline_table_start0
+
+	.section	.offset_05,"",@progbits
+	.quad	my_label_04-.Lline_table_start0