From 861178d373072c953bf5901bdef982be042be26f Mon Sep 17 00:00:00 2001
From: Eric Christopher <echristo@gmail.com>
Date: Fri, 31 Jan 2014 20:02:58 +0000
Subject: [PATCH] Add support for DW_FORM_flag and DW_FORM_flag_present to the
 DIE hashing algorithm. Sink the 'A' + Attribute hash into each form so we
 don't have to check valid forms before deciding whether or not we're going to
 hash which will let the default be to return without doing anything.

llvm-svn: 200571
---
 lib/CodeGen/AsmPrinter/DIEHash.cpp | 29 ++++++++++++++++++----------
 unittests/CodeGen/DIEHashTest.cpp  | 31 ++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/lib/CodeGen/AsmPrinter/DIEHash.cpp b/lib/CodeGen/AsmPrinter/DIEHash.cpp
index ca10939d653..72be1b59501 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.cpp
+++ b/lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -284,22 +284,20 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
     return;
   }
 
-  // Other attribute values use the letter 'A' as the marker, ...
-  addULEB128('A');
-
-  addULEB128(Attribute);
-
-  // ... and the value consists of the form code (encoded as an unsigned LEB128
-  // value) followed by the encoding of the value according to the form code. To
-  // ensure reproducibility of the signature, the set of forms used in the
-  // signature computation is limited to the following: DW_FORM_sdata,
-  // DW_FORM_flag, DW_FORM_string, and DW_FORM_block.
+  // Other attribute values use the letter 'A' as the marker, and the value
+  // consists of the form code (encoded as an unsigned LEB128 value) followed by
+  // the encoding of the value according to the form code. To ensure
+  // reproducibility of the signature, the set of forms used in the signature
+  // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag,
+  // DW_FORM_string, and DW_FORM_block.
   switch (Desc->getForm()) {
   case dwarf::DW_FORM_string:
     llvm_unreachable(
         "Add support for DW_FORM_string if we ever start emitting them again");
   case dwarf::DW_FORM_GNU_str_index:
   case dwarf::DW_FORM_strp:
+    addULEB128('A');
+    addULEB128(Attribute);
     addULEB128(dwarf::DW_FORM_string);
     addString(cast<DIEString>(Value)->getString());
     break;
@@ -308,9 +306,20 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
   case dwarf::DW_FORM_data4:
   case dwarf::DW_FORM_data8:
   case dwarf::DW_FORM_udata:
+    addULEB128('A');
+    addULEB128(Attribute);
     addULEB128(dwarf::DW_FORM_sdata);
     addSLEB128((int64_t)cast<DIEInteger>(Value)->getValue());
     break;
+  // DW_FORM_flag_present is just flag with a value of one. We still give it a
+  // value so just use the value.
+  case dwarf::DW_FORM_flag_present:
+  case dwarf::DW_FORM_flag:
+    addULEB128('A');
+    addULEB128(Attribute);
+    addULEB128(dwarf::DW_FORM_flag);
+    addULEB128((int64_t)cast<DIEInteger>(Value)->getValue());
+    break;
   default:
     llvm_unreachable("Add support for additional forms");
   }
diff --git a/unittests/CodeGen/DIEHashTest.cpp b/unittests/CodeGen/DIEHashTest.cpp
index 9faeaafc245..a70870cbbae 100644
--- a/unittests/CodeGen/DIEHashTest.cpp
+++ b/unittests/CodeGen/DIEHashTest.cpp
@@ -514,4 +514,35 @@ TEST(DIEHashTest, MemberFunc) {
   // The exact same hash GCC produces for this DIE.
   ASSERT_EQ(0xd36a1b6dfb604ba0ULL, MD5Res);
 }
+
+// struct A {
+//   static void func();
+// };
+TEST(DIEHashTest, MemberFuncFlag) {
+  DIE A(dwarf::DW_TAG_structure_type);
+  DIEInteger One(1);
+  DIEString AStr(&One, "A");
+  A.addValue(dwarf::DW_AT_name, dwarf::DW_FORM_strp, &AStr);
+  A.addValue(dwarf::DW_AT_byte_size, dwarf::DW_FORM_data1, &One);
+  A.addValue(dwarf::DW_AT_decl_file, dwarf::DW_FORM_data1, &One);
+  A.addValue(dwarf::DW_AT_decl_line, dwarf::DW_FORM_data1, &One);
+
+  DIE *Func = new DIE(dwarf::DW_TAG_subprogram);
+  DIEString FuncStr(&One, "func");
+  DIEString FuncLinkage(&One, "_ZN1A4funcEv");
+  DIEInteger Two(2);
+  Func->addValue(dwarf::DW_AT_external, dwarf::DW_FORM_flag_present, &One);
+  Func->addValue(dwarf::DW_AT_name, dwarf::DW_FORM_strp, &FuncStr);
+  Func->addValue(dwarf::DW_AT_decl_file, dwarf::DW_FORM_data1, &One);
+  Func->addValue(dwarf::DW_AT_decl_line, dwarf::DW_FORM_data1, &Two);
+  Func->addValue(dwarf::DW_AT_linkage_name, dwarf::DW_FORM_strp, &FuncLinkage);
+  Func->addValue(dwarf::DW_AT_declaration, dwarf::DW_FORM_flag_present, &One);
+
+  A.addChild(Func);
+
+  uint64_t MD5Res = DIEHash().computeTypeSignature(A);
+
+  // The exact same hash GCC produces for this DIE.
+  ASSERT_EQ(0x8f78211ddce3df10ULL, MD5Res);
+}
 }