diff --git a/include/llvm/CodeGen/MachineBasicBlock.h b/include/llvm/CodeGen/MachineBasicBlock.h
index 5a20e952b9c..499f62d660f 100644
--- a/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/include/llvm/CodeGen/MachineBasicBlock.h
@@ -84,8 +84,9 @@ class MachineBasicBlock : public ilist_node<MachineBasicBlock> {
 
   /// Alignment - Alignment of the basic block. Zero if the basic block does
   /// not need to be aligned.
+  /// The alignment is specified as log2(bytes).
   unsigned Alignment;
-  
+
   /// IsLandingPad - Indicate that this basic block is entered via an
   /// exception handler.
   bool IsLandingPad;
@@ -219,10 +220,12 @@ public:
   bool            livein_empty() const { return LiveIns.empty(); }
 
   /// getAlignment - Return alignment of the basic block.
+  /// The alignment is specified as log2(bytes).
   ///
   unsigned getAlignment() const { return Alignment; }
 
   /// setAlignment - Set alignment of the basic block.
+  /// The alignment is specified as log2(bytes).
   ///
   void setAlignment(unsigned Align) { Alignment = Align; }
 
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index d60a1f1e0a5..8c69a3aca81 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1970,7 +1970,7 @@ static void EmitBasicBlockLoopComments(const MachineBasicBlock &MBB,
 void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock *MBB) const {
   // Emit an alignment directive for this block, if needed.
   if (unsigned Align = MBB->getAlignment())
-    EmitAlignment(Log2_32(Align));
+    EmitAlignment(Align);
 
   // If the block has its address taken, emit any labels that were used to
   // reference the block.  It is possible that there is more than one label
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index a67d27568d0..a214c06c3b5 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1211,10 +1211,10 @@ X86TargetLowering::X86TargetLowering(X86TargetMachine &TM)
   maxStoresPerMemcpyOptSize = Subtarget->isTargetDarwin() ? 8 : 4;
   maxStoresPerMemmove = 8; // For @llvm.memmove -> sequence of stores
   maxStoresPerMemmoveOptSize = Subtarget->isTargetDarwin() ? 8 : 4;
-  setPrefLoopAlignment(16);
+  setPrefLoopAlignment(4); // 2^4 bytes.
   benefitFromCodePlacementOpt = true;
 
-  setPrefFunctionAlignment(4);
+  setPrefFunctionAlignment(4); // 2^4 bytes.
 }