dwarfgen: Add support for generating the debug_str_offsets section, take 2

This recommits r337910 after fixing an "ambiguous call to addAttribute"
error with some compilers (gcc circa 4.9 and MSVC). It seems that these
compilers will consider a "false -> pointer" conversion during overload
resolution. This creates ambiguity because one I added an overload which
takes a MCExpr * as an argument.

I fix this by making the new overload take MCExpr&, which avoids the
conversion. It also documents the fact that we expect a valid MCExpr
object.

Original commit message follows:

The motivation for this is D49493, where we'd like to test details of
debug_str_offsets behavior which is difficult to trigger from a
traditional test.

This adds the plubming necessary for dwarfgen to generate this section.
The more interesting changes are:
- I've moved emitStringOffsetsTableHeader function from DwarfFile to
  DwarfStringPool, so I can generate the section header more easily from
  the unit test.
- added a new addAttribute overload taking an MCExpr*. This is used to
  generate the DW_AT_str_offsets_base, which links a compile unit to the
  offset table.

I've also added a basic test for reading and writing DW_form_strx forms.

Reviewers: dblaikie, JDevlieghere, probinson

Subscribers: llvm-commits, aprantl

Differential Revision: https://reviews.llvm.org/D49670

llvm-svn: 337933

1 files changed, 48 insertions, 2 deletions

diff --git a/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
index 6b26318802a..60058be2e81 100644
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
@@ -67,12 +67,23 @@ void TestAllForms() {
   const uint32_t Dwarf32Values[] = {1, 2, 3, 4, 5, 6, 7, 8};
   const char *StringValue = "Hello";
   const char *StrpValue = "World";
+  const char *StrxValue = "Indexed";
+  const char *Strx1Value = "Indexed1";
+  const char *Strx2Value = "Indexed2";
+  const char *Strx3Value = "Indexed3";
+  const char *Strx4Value = "Indexed4";
 
   auto ExpectedDG = dwarfgen::Generator::create(Triple, Version);
   ASSERT_THAT_EXPECTED(ExpectedDG, Succeeded());
   dwarfgen::Generator *DG = ExpectedDG.get().get();
   dwarfgen::CompileUnit &CU = DG->addCompileUnit();
   dwarfgen::DIE CUDie = CU.getUnitDIE();
+
+  if (Version >= 5)
+    CUDie.addAttribute(dwarf::DW_AT_str_offsets_base, dwarf::DW_FORM_sec_offset,
+                       *MCSymbolRefExpr::create(DG->getStringOffsetsStartSym(),
+                                                *DG->getMCContext()));
+
   uint16_t Attr = DW_AT_lo_user;
 
   //----------------------------------------------------------------------
@@ -122,6 +133,19 @@ void TestAllForms() {
   const auto Attr_DW_FORM_string = static_cast<dwarf::Attribute>(Attr++);
   CUDie.addAttribute(Attr_DW_FORM_string, DW_FORM_string, StringValue);
 
+  const auto Attr_DW_FORM_strx = static_cast<dwarf::Attribute>(Attr++);
+  const auto Attr_DW_FORM_strx1 = static_cast<dwarf::Attribute>(Attr++);
+  const auto Attr_DW_FORM_strx2 = static_cast<dwarf::Attribute>(Attr++);
+  const auto Attr_DW_FORM_strx3 = static_cast<dwarf::Attribute>(Attr++);
+  const auto Attr_DW_FORM_strx4 = static_cast<dwarf::Attribute>(Attr++);
+  if (Version >= 5) {
+    CUDie.addAttribute(Attr_DW_FORM_strx, DW_FORM_strx, StrxValue);
+    CUDie.addAttribute(Attr_DW_FORM_strx1, DW_FORM_strx1, Strx1Value);
+    CUDie.addAttribute(Attr_DW_FORM_strx2, DW_FORM_strx2, Strx2Value);
+    CUDie.addAttribute(Attr_DW_FORM_strx3, DW_FORM_strx3, Strx3Value);
+    CUDie.addAttribute(Attr_DW_FORM_strx4, DW_FORM_strx4, Strx4Value);
+  }
+
   const auto Attr_DW_FORM_strp = static_cast<dwarf::Attribute>(Attr++);
   CUDie.addAttribute(Attr_DW_FORM_strp, DW_FORM_strp, StrpValue);
 
@@ -281,11 +305,33 @@ void TestAllForms() {
   //----------------------------------------------------------------------
   auto ExtractedStringValue = toString(DieDG.find(Attr_DW_FORM_string));
   EXPECT_TRUE((bool)ExtractedStringValue);
-  EXPECT_TRUE(strcmp(StringValue, *ExtractedStringValue) == 0);
+  EXPECT_STREQ(StringValue, *ExtractedStringValue);
+
+  if (Version >= 5) {
+    auto ExtractedStrxValue = toString(DieDG.find(Attr_DW_FORM_strx));
+    EXPECT_TRUE((bool)ExtractedStrxValue);
+    EXPECT_STREQ(StrxValue, *ExtractedStrxValue);
+
+    auto ExtractedStrx1Value = toString(DieDG.find(Attr_DW_FORM_strx1));
+    EXPECT_TRUE((bool)ExtractedStrx1Value);
+    EXPECT_STREQ(Strx1Value, *ExtractedStrx1Value);
+
+    auto ExtractedStrx2Value = toString(DieDG.find(Attr_DW_FORM_strx2));
+    EXPECT_TRUE((bool)ExtractedStrx2Value);
+    EXPECT_STREQ(Strx2Value, *ExtractedStrx2Value);
+
+    auto ExtractedStrx3Value = toString(DieDG.find(Attr_DW_FORM_strx3));
+    EXPECT_TRUE((bool)ExtractedStrx3Value);
+    EXPECT_STREQ(Strx3Value, *ExtractedStrx3Value);
+
+    auto ExtractedStrx4Value = toString(DieDG.find(Attr_DW_FORM_strx4));
+    EXPECT_TRUE((bool)ExtractedStrx4Value);
+    EXPECT_STREQ(Strx4Value, *ExtractedStrx4Value);
+  }
 
   auto ExtractedStrpValue = toString(DieDG.find(Attr_DW_FORM_strp));
   EXPECT_TRUE((bool)ExtractedStrpValue);
-  EXPECT_TRUE(strcmp(StrpValue, *ExtractedStrpValue) == 0);
+  EXPECT_STREQ(StrpValue, *ExtractedStrpValue);
 
   //----------------------------------------------------------------------
   // Test reference forms