Fix line table lookups in line tables with multiple lines with the sa… (

#70879)

Fix line table lookups in line tables with multiple lines with the same
address.

Compilers emit line tables that have multiple line table entries with
the same address. When doing lookups, we always need to use the last
line entry if a lookup address matches the address of one or more line
entries. This is because the size of an address range for a line uses
the next line entry to figure out how big the current line entry is. If
the next line entry has the same address, that means the current line
entry has a size of zero, so no bytes correspond to the line entry.

This patch ensures that lookups will always pick the last matching line
entry when the lookup address matches more than one line entry.

llvm/lib/DebugInfo/GSYM/LineTable.cpp

@@ -270,11 +270,6 @@ Expected<LineEntry> LineTable::lookup(DataExtractor &Data, uint64_t BaseAddr, ui
     if (Addr < Row.Addr)
       return false; // Stop parsing, result contains the line table row!
     Result = Row;
-    if (Addr == Row.Addr) {
-      // Stop parsing, this is the row we are looking for since the address
-      // matches.
-      return false;
-    }
     return true; // Keep parsing till we find the right row.
   });
   if (Err)

llvm/unittests/DebugInfo/GSYM/GSYMTest.cpp

@@ -4156,3 +4156,172 @@ TEST(GSYMTest, TestEmptyLinkageName) {
   // Make sure we don't see spurious errors in the output:
   EXPECT_TRUE(errors.find("error:") == std::string::npos);
 }
+
+TEST(GSYMTest, TestLineTablesWithEmptyRanges) {
+  // Test that lookups find the right line table entry when there are multiple
+  // line entries with the same address. When we have multiple line table
+  // entries with the same address, we need to pick the last one in the line
+  // table. We do this because a line entry's start address in the defined by
+  // the line table entry's address and the size is determined by the
+  // subtracting the next line table's address. If the current line table
+  // entry's address is the same as the next one, then there is no code
+  // assiciated with the current line table entry and it should be ignored.
+  //
+  // 0x0000000b: DW_TAG_compile_unit
+  //               DW_AT_name        ("/tmp/main.cpp")
+  //               DW_AT_language    (DW_LANG_C)
+  //               DW_AT_stmt_list   (0x00000000)
+  //
+  // 0x00000015:   DW_TAG_subprogram
+  //                 DW_AT_name      ("foo")
+  //                 DW_AT_low_pc    (0x0000000000001000)
+  //                 DW_AT_high_pc   (0x0000000000001050)
+  //
+  // 0x0000002a:   NULL
+  //
+  // The line table has a duplicate entry at 0x1010:
+  //
+  // Address    Line   Column File   ISA Discriminator Flags
+  // ---------- ------ ------ ------ --- ------------- -------------
+  // 0x00001000     10      0      1   0             0  is_stmt
+  // 0x00001010     11      0      1   0             0  is_stmt
+  // 0x00001010     12      0      1   0             0  is_stmt
+  // 0x00001050     13      0      1   0             0  is_stmt end_sequence
+
+  StringRef yamldata = R"(
+  debug_str:
+    - ''
+    - '/tmp/main.cpp'
+    - foo
+  debug_abbrev:
+    - ID:              0
+      Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_yes
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_language
+              Form:            DW_FORM_udata
+            - Attribute:       DW_AT_stmt_list
+              Form:            DW_FORM_sec_offset
+        - Code:            0x2
+          Tag:             DW_TAG_subprogram
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_low_pc
+              Form:            DW_FORM_addr
+            - Attribute:       DW_AT_high_pc
+              Form:            DW_FORM_addr
+  debug_info:
+    - Length:          0x27
+      Version:         4
+      AbbrevTableID:   0
+      AbbrOffset:      0x0
+      AddrSize:        8
+      Entries:
+        - AbbrCode:        0x1
+          Values:
+            - Value:           0x1
+            - Value:           0x2
+            - Value:           0x0
+        - AbbrCode:        0x2
+          Values:
+            - Value:           0xF
+            - Value:           0x1000
+            - Value:           0x1050
+        - AbbrCode:        0x0
+  debug_line:
+    - Length:          71
+      Version:         2
+      PrologueLength:  36
+      MinInstLength:   1
+      DefaultIsStmt:   1
+      LineBase:        251
+      LineRange:       14
+      OpcodeBase:      13
+      StandardOpcodeLengths: [ 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 ]
+      IncludeDirs:
+        - '/tmp'
+      Files:
+        - Name:            main.cpp
+          DirIdx:          1
+          ModTime:         0
+          Length:          0
+      Opcodes:
+        - Opcode:          DW_LNS_extended_op
+          ExtLen:          9
+          SubOpcode:       DW_LNE_set_address
+          Data:            4096
+        - Opcode:          DW_LNS_advance_line
+          SData:           9
+          Data:            0
+        - Opcode:          DW_LNS_copy
+          Data:            0
+        - Opcode:          DW_LNS_advance_pc
+          Data:            16
+        - Opcode:          DW_LNS_advance_line
+          SData:           1
+          Data:            0
+        - Opcode:          DW_LNS_copy
+          Data:            0
+        - Opcode:          DW_LNS_advance_line
+          SData:           1
+          Data:            0
+        - Opcode:          DW_LNS_copy
+          Data:            0
+        - Opcode:          DW_LNS_advance_pc
+          Data:            64
+        - Opcode:          DW_LNS_advance_line
+          SData:           1
+          Data:            0
+        - Opcode:          DW_LNS_extended_op
+          ExtLen:          1
+          SubOpcode:       DW_LNE_end_sequence
+          Data:            0
+  )";
+  auto ErrOrSections = DWARFYAML::emitDebugSections(yamldata);
+  ASSERT_THAT_EXPECTED(ErrOrSections, Succeeded());
+  std::unique_ptr<DWARFContext> DwarfContext =
+      DWARFContext::create(*ErrOrSections, 8);
+  ASSERT_TRUE(DwarfContext.get() != nullptr);
+  std::string errors;
+  raw_string_ostream OS(errors);
+  GsymCreator GC;
+  DwarfTransformer DT(*DwarfContext, GC);
+  const uint32_t ThreadCount = 1;
+  ASSERT_THAT_ERROR(DT.convert(ThreadCount, &OS), Succeeded());
+  ASSERT_THAT_ERROR(GC.finalize(OS), Succeeded());
+  OS.flush();
+  SmallString<512> Str;
+  raw_svector_ostream OutStrm(Str);
+  const auto ByteOrder = llvm::endianness::native;
+  FileWriter FW(OutStrm, ByteOrder);
+  ASSERT_THAT_ERROR(GC.encode(FW), Succeeded());
+  Expected<GsymReader> GR = GsymReader::copyBuffer(OutStrm.str());
+  ASSERT_THAT_EXPECTED(GR, Succeeded());
+  // There should be one function in our GSYM.
+  EXPECT_EQ(GR->getNumAddresses(), 1u);
+  // Verify "foo" is present and has a line table and no inline info.
+  auto ExpFI = GR->getFunctionInfo(0x1000);
+  ASSERT_THAT_EXPECTED(ExpFI, Succeeded());
+  ASSERT_EQ(ExpFI->Range, AddressRange(0x1000, 0x1050));
+  EXPECT_TRUE(ExpFI->OptLineTable.has_value());
+  EXPECT_FALSE(ExpFI->Inline.has_value());
+  StringRef FuncName = GR->getString(ExpFI->Name);
+  EXPECT_EQ(FuncName, "foo");
+
+  // Make sure we don't see spurious errors in the output:
+  EXPECT_TRUE(errors.find("error:") == std::string::npos);
+
+  // Make sure that when we lookup address 0x1010, that we get the entry that
+  // matches line 12, the second line entry that also has the address of
+  // 0x1010.
+  auto LR = GR->lookup(0x1010);
+  ASSERT_THAT_EXPECTED(LR, Succeeded());
+  SourceLocation src_loc = {"foo", "/tmp", "main.cpp", 12, 16};
+  EXPECT_THAT(LR->Locations, testing::ElementsAre(src_loc));
+git}