From a954618c6e6c5f94d3cedc0b6bc19dbc49e56ac2 Mon Sep 17 00:00:00 2001
From: David Blaikie <dblaikie@gmail.com>
Date: Fri, 25 Oct 2013 18:38:43 +0000
Subject: DIEHash: Summary hashing of nested types

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193427 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Support/Dwarf.h       | 28 ++++++++++++++++++++++++++++
 lib/CodeGen/AsmPrinter/DIEHash.cpp | 25 ++++++++++++++++++++++++-
 lib/CodeGen/AsmPrinter/DIEHash.h   |  2 ++
 unittests/CodeGen/DIEHashTest.cpp  | 19 +++++++++++++++++++
 4 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/include/llvm/Support/Dwarf.h b/include/llvm/Support/Dwarf.h
index f3f42741ef..23bbd1c384 100644
--- a/include/llvm/Support/Dwarf.h
+++ b/include/llvm/Support/Dwarf.h
@@ -141,6 +141,34 @@ enum Tag LLVM_ENUM_INT_TYPE(uint16_t) {
   DW_TAG_hi_user = 0xffff
 };
 
+inline bool isType(Tag T) {
+  switch (T) {
+  case DW_TAG_array_type:
+  case DW_TAG_class_type:
+  case DW_TAG_interface_type:
+  case DW_TAG_enumeration_type:
+  case DW_TAG_pointer_type:
+  case DW_TAG_reference_type:
+  case DW_TAG_rvalue_reference_type:
+  case DW_TAG_string_type:
+  case DW_TAG_structure_type:
+  case DW_TAG_subroutine_type:
+  case DW_TAG_union_type:
+  case DW_TAG_ptr_to_member_type:
+  case DW_TAG_set_type:
+  case DW_TAG_subrange_type:
+  case DW_TAG_base_type:
+  case DW_TAG_const_type:
+  case DW_TAG_file_type:
+  case DW_TAG_packed_type:
+  case DW_TAG_volatile_type:
+  case DW_TAG_typedef:
+    return true;
+  default:
+    return false;
+  }
+}
+
 enum Attribute LLVM_ENUM_INT_TYPE(uint16_t) {
   // Attributes
   DW_AT_sibling = 0x01,
diff --git a/lib/CodeGen/AsmPrinter/DIEHash.cpp b/lib/CodeGen/AsmPrinter/DIEHash.cpp
index b8b2bd2205..18264672ed 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.cpp
+++ b/lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -384,6 +384,18 @@ void DIEHash::addAttributes(const DIE &Die) {
   hashAttributes(Attrs, Die.getTag());
 }
 
+void DIEHash::hashNestedType(const DIE &Die, StringRef Name) {
+  // 7.27 Step 7
+  // ... append the letter 'S',
+  addULEB128('S');
+
+  // the tag of C,
+  addULEB128(Die.getTag());
+
+  // and the name.
+  addString(Name);
+}
+
 // Compute the hash of a DIE. This is based on the type signature computation
 // given in section 7.27 of the DWARF4 standard. It is the md5 hash of a
 // flattened description of the DIE.
@@ -398,8 +410,19 @@ void DIEHash::computeHash(const DIE &Die) {
   // Then hash each of the children of the DIE.
   for (std::vector<DIE *>::const_iterator I = Die.getChildren().begin(),
                                           E = Die.getChildren().end();
-       I != E; ++I)
+       I != E; ++I) {
+    // 7.27 Step 7
+    // If C is a nested type entry or a member function entry, ...
+    if (isType((*I)->getTag())) {
+      StringRef Name = getDIEStringAttr(**I, dwarf::DW_AT_name);
+      // ... and has a DW_AT_name attribute
+      if (!Name.empty()) {
+        hashNestedType(**I, Name);
+        continue;
+      }
+    }
     computeHash(**I);
+  }
 
   // Following the last (or if there are no children), append a zero byte.
   Hash.update(makeArrayRef((uint8_t)'\0'));
diff --git a/lib/CodeGen/AsmPrinter/DIEHash.h b/lib/CodeGen/AsmPrinter/DIEHash.h
index da373de3f0..b9cf7ce949 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.h
+++ b/lib/CodeGen/AsmPrinter/DIEHash.h
@@ -137,6 +137,8 @@ private:
   /// \brief Hashes a reference to a previously referenced type DIE.
   void hashRepeatedTypeReference(dwarf::Attribute Attribute, unsigned DieNumber);
 
+  void hashNestedType(const DIE &Die, StringRef Name);
+
 private:
   MD5 Hash;
   DenseMap<const DIE *, unsigned> Numbering;
diff --git a/unittests/CodeGen/DIEHashTest.cpp b/unittests/CodeGen/DIEHashTest.cpp
index 6f71462bfd..fb6f4b3640 100644
--- a/unittests/CodeGen/DIEHashTest.cpp
+++ b/unittests/CodeGen/DIEHashTest.cpp
@@ -477,4 +477,23 @@ TEST(DIEHashTest, RefUnnamedType) {
 
   ASSERT_EQ(0x954e026f01c02529ULL, MD5Res);
 }
+
+// struct { struct bar { }; };
+TEST(DIEHashTest, NestedType) {
+  DIE Unnamed(dwarf::DW_TAG_structure_type);
+  DIEInteger One(1);
+  Unnamed.addValue(dwarf::DW_AT_byte_size, dwarf::DW_FORM_data1, &One);
+
+  DIE *Foo = new DIE(dwarf::DW_TAG_structure_type);
+  DIEString FooStr(&One, "foo");
+  Foo->addValue(dwarf::DW_AT_name, dwarf::DW_FORM_strp, &FooStr);
+  Foo->addValue(dwarf::DW_AT_byte_size, dwarf::DW_FORM_data1, &One);
+
+  Unnamed.addChild(Foo);
+
+  uint64_t MD5Res = DIEHash().computeTypeSignature(Unnamed);
+
+  // The exact same hash GCC produces for this DIE.
+  ASSERT_EQ(0xde8a3b7b43807f4aULL, MD5Res);
+}
 }
-- 
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