From 13b58ec74ade26579f1dfba872564396670e56c0 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Tue, 30 Jun 2015 00:03:56 +0000
Subject: [PATCH] Object/COFF: Define coff_symbol_generic.

If you only need Name and Value fields in the COFF symbol,
you don't need to distinguish 32 bit and 64 bit COFF symbols.
These fields start at the same offsets and have the same size.

This data strucutre is one pointer smaller than COFFSymbolRef
thus slightly efficient. I'll use this class in LLD as we create
millions of LLD symbol objects that currently contain COFFSymbolRef.
Shaving off 8 byte (or 4 byte on 32 bit) from that class actually
matters becasue of the number of objects we create in LLD.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241024 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Object/COFF.h    | 17 +++++++++++++++++
 lib/Object/COFFObjectFile.cpp | 16 ++++++++++------
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/include/llvm/Object/COFF.h b/include/llvm/Object/COFF.h
index bdd1a6c877d..ce12aab6fba 100644
--- a/include/llvm/Object/COFF.h
+++ b/include/llvm/Object/COFF.h
@@ -249,6 +249,15 @@ struct coff_symbol {
 typedef coff_symbol<support::ulittle16_t> coff_symbol16;
 typedef coff_symbol<support::ulittle32_t> coff_symbol32;
 
+// Contains only common parts of coff_symbol16 and coff_symbol32.
+struct coff_symbol_generic {
+  union {
+    char ShortName[COFF::NameSize];
+    StringTableOffset Offset;
+  } Name;
+  support::ulittle32_t Value;
+};
+
 class COFFSymbolRef {
 public:
   COFFSymbolRef(const coff_symbol16 *CS) : CS16(CS), CS32(nullptr) {}
@@ -259,6 +268,12 @@ public:
     return CS16 ? static_cast<const void *>(CS16) : CS32;
   }
 
+  const coff_symbol_generic *getGeneric() const {
+    if (CS16)
+      return reinterpret_cast<const coff_symbol_generic *>(CS16);
+    return reinterpret_cast<const coff_symbol_generic *>(CS32);
+  }
+
   friend bool operator<(COFFSymbolRef A, COFFSymbolRef B) {
     return A.getRawPtr() < B.getRawPtr();
   }
@@ -744,6 +759,8 @@ public:
     return std::error_code();
   }
   std::error_code getSymbolName(COFFSymbolRef Symbol, StringRef &Res) const;
+  std::error_code getSymbolName(const coff_symbol_generic *Symbol,
+                                StringRef &Res) const;
 
   ArrayRef<uint8_t> getSymbolAuxData(COFFSymbolRef Symbol) const;
 
diff --git a/lib/Object/COFFObjectFile.cpp b/lib/Object/COFFObjectFile.cpp
index 3e55cc1bf92..6263d32db8c 100644
--- a/lib/Object/COFFObjectFile.cpp
+++ b/lib/Object/COFFObjectFile.cpp
@@ -847,20 +847,24 @@ std::error_code COFFObjectFile::getString(uint32_t Offset,
 
 std::error_code COFFObjectFile::getSymbolName(COFFSymbolRef Symbol,
                                               StringRef &Res) const {
+  return getSymbolName(Symbol.getGeneric(), Res);
+}
+
+std::error_code COFFObjectFile::getSymbolName(const coff_symbol_generic *Symbol,
+                                              StringRef &Res) const {
   // Check for string table entry. First 4 bytes are 0.
-  if (Symbol.getStringTableOffset().Zeroes == 0) {
-    uint32_t Offset = Symbol.getStringTableOffset().Offset;
-    if (std::error_code EC = getString(Offset, Res))
+  if (Symbol->Name.Offset.Zeroes == 0) {
+    if (std::error_code EC = getString(Symbol->Name.Offset.Offset, Res))
       return EC;
     return std::error_code();
   }
 
-  if (Symbol.getShortName()[COFF::NameSize - 1] == 0)
+  if (Symbol->Name.ShortName[COFF::NameSize - 1] == 0)
     // Null terminated, let ::strlen figure out the length.
-    Res = StringRef(Symbol.getShortName());
+    Res = StringRef(Symbol->Name.ShortName);
   else
     // Not null terminated, use all 8 bytes.
-    Res = StringRef(Symbol.getShortName(), COFF::NameSize);
+    Res = StringRef(Symbol->Name.ShortName, COFF::NameSize);
   return std::error_code();
 }
 
-- 
2.34.1