From 4d9c5397b4a3be747bdb73f1d24c3fdbaaf438fe Mon Sep 17 00:00:00 2001
From: "Michael J. Spencer" <bigcheesegs@gmail.com>
Date: Fri, 4 Jan 2013 20:36:28 +0000
Subject: [Object][ELF] Add a maximum alignment. This is used by
 createELFObjectFile to create a properly aligned reader.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171520 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Object/ELFObjectFile.cpp | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

(limited to 'lib/Object')

diff --git a/lib/Object/ELFObjectFile.cpp b/lib/Object/ELFObjectFile.cpp
index 663b84e..2c8c1b1 100644
--- a/lib/Object/ELFObjectFile.cpp
+++ b/lib/Object/ELFObjectFile.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Object/ELF.h"
+#include "llvm/Support/MathExtras.h"
 
 namespace llvm {
 
@@ -22,16 +23,37 @@ ObjectFile *ObjectFile::createELFObjectFile(MemoryBuffer *Object) {
   std::pair<unsigned char, unsigned char> Ident = getElfArchType(Object);
   error_code ec;
 
+  std::size_t MaxAlignment =
+    1ULL << CountTrailingZeros_64(uintptr_t(Object->getBufferStart()));
+
   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB)
-    return new ELFObjectFile<support::little, false>(Object, ec);
+    if (MaxAlignment >= 4)
+      return new ELFObjectFile<support::little, 4, false>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::little, 2, false>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB)
-    return new ELFObjectFile<support::big, false>(Object, ec);
+    if (MaxAlignment >= 4)
+      return new ELFObjectFile<support::big, 4, false>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::big, 2, false>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB)
-    return new ELFObjectFile<support::big, true>(Object, ec);
+    if (MaxAlignment >= 8)
+      return new ELFObjectFile<support::big, 8, true>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::big, 2, true>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
-    ELFObjectFile<support::little, true> *result =
-          new ELFObjectFile<support::little, true>(Object, ec);
-    return result;
+    if (MaxAlignment >= 8)
+      return new ELFObjectFile<support::little, 8, true>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::little, 2, true>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   }
 
   report_fatal_error("Buffer is not an ELF object file!");
-- 
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