[PATCH] D30456: [DebugInfo] Unique abbrevs for DIEs with different implicit_const values

[Victor Leschuk via Phabricator via llvm-commits]

vleschuk created this revision.
Herald added a subscriber: mehdi_amini.

Take DW_FORM_implicit_const attribute value into account when profiling DIEAbbrevData.

Currently if we have two similar types with implicit_const attributes and different values we end up with only one abbrev in .debug_abbrev section. For example consider two structures: S1 with implicit_const attribute ATTR and value VAL1 and S2 with implicit_const ATTR and value VAL2. The .debug_abbrev section will contain only 1 related record:

  [N] DW_TAG_structure_type       DW_CHILDREN_yes
          DW_AT_ATTR        DW_FORM_implicit_const  VAL1
          // ....

This is incorrect as struct S2 (with VAL2) will use abbrev record with VAL1.

With this patch we will have two different abbreviations here:

  [N] DW_TAG_structure_type       DW_CHILDREN_yes
          DW_AT_ATTR        DW_FORM_implicit_const  VAL1
          // ....
  
  [M] DW_TAG_structure_type       DW_CHILDREN_yes
          DW_AT_ATTR        DW_FORM_implicit_const  VAL2
          // ....


https://reviews.llvm.org/D30456

Files:
  lib/CodeGen/AsmPrinter/DIE.cpp
  unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
  unittests/DebugInfo/DWARF/DwarfGenerator.h


Index: unittests/DebugInfo/DWARF/DwarfGenerator.h
===================================================================
--- unittests/DebugInfo/DWARF/DwarfGenerator.h
+++ unittests/DebugInfo/DWARF/DwarfGenerator.h
@@ -132,6 +132,9 @@
   
   /// Force a DIE to say it has children even when it doesn't.
   void setForceChildren();
+
+  /// Get actual DIE object
+  llvm::DIE &getDIE() { return *Die; }
 };
 
 /// A DWARF compile unit used to generate DWARF compile/type units.
Index: unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
===================================================================
--- unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
+++ unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp
@@ -1543,4 +1543,38 @@
   EXPECT_EQ(DieMangled, toString(NameOpt, ""));
 }
 
+TEST(DWARFDebugInfo, TestImplicitConstAbbrevs) {
+  uint16_t Version = 5;
+
+  const uint8_t AddrSize = sizeof(void *);
+  initLLVMIfNeeded();
+  Triple Triple = getHostTripleForAddrSize(AddrSize);
+  auto ExpectedDG = dwarfgen::Generator::create(Triple, Version);
+  if (HandleExpectedError(ExpectedDG))
+    return;
+  dwarfgen::Generator *DG = ExpectedDG.get().get();
+  dwarfgen::CompileUnit &CU = DG->addCompileUnit();
+  dwarfgen::DIE CUDie = CU.getUnitDIE();
+  uint16_t Attr = DW_AT_lo_user;
+  int64_t Val1 = 42;
+  int64_t Val2 = 43;
+
+  auto &AbbrevSet = DG->getAbbrevSet();
+  auto FirstVal1DIE = CUDie.addChild(DW_TAG_class_type);
+  FirstVal1DIE.addAttribute(Attr, DW_FORM_implicit_const, Val1);
+  auto &FirstVal1Abbrev = AbbrevSet.uniqueAbbreviation(FirstVal1DIE.getDIE());
+
+  auto SecondVal1DIE = CUDie.addChild(DW_TAG_class_type);
+  SecondVal1DIE.addAttribute(Attr, DW_FORM_implicit_const, Val1);
+  auto &SecondVal1Abbrev = AbbrevSet.uniqueAbbreviation(SecondVal1DIE.getDIE());
+
+  EXPECT_EQ(FirstVal1Abbrev.getNumber(), SecondVal1Abbrev.getNumber());
+
+  auto Val2DIE = CUDie.addChild(DW_TAG_class_type);
+  Val2DIE.addAttribute(Attr, DW_FORM_implicit_const, Val2);
+  auto &Val2Abbrev = AbbrevSet.uniqueAbbreviation(Val2DIE.getDIE());
+
+  EXPECT_NE(FirstVal1Abbrev.getNumber(), Val2Abbrev.getNumber());
+}
+
 } // end anonymous namespace
Index: lib/CodeGen/AsmPrinter/DIE.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DIE.cpp
+++ lib/CodeGen/AsmPrinter/DIE.cpp
@@ -42,6 +42,8 @@
   // overloads.  Otherwise MSVC 2010 thinks this call is ambiguous.
   ID.AddInteger(unsigned(Attribute));
   ID.AddInteger(unsigned(Form));
+  if (dwarf::DW_FORM_implicit_const == Form)
+    ID.AddInteger(Value);
 }
 
 //===----------------------------------------------------------------------===//
@@ -107,8 +109,12 @@
     O << "  "
       << dwarf::AttributeString(Data[i].getAttribute())
       << "  "
-      << dwarf::FormEncodingString(Data[i].getForm())
-      << '\n';
+      << dwarf::FormEncodingString(Data[i].getForm());
+
+    if (dwarf::DW_FORM_implicit_const == Data[i].getForm())
+      O << " " << Data[i].getValue();
+
+    O << '\n';
   }
 }
 


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