Add a method for allocating space from the code buffer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28064 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineCodeEmitter.h

@@ -140,6 +140,28 @@ public:
     }
   }
 
+  /// allocateSpace - Allocate a block of space in the current output buffer,
+  /// returning null (and setting conditions to indicate buffer overflow) on
+  /// failure.  Alignment is the alignment in bytes of the buffer desired.
+  void *allocateSpace(intptr_t Size, unsigned Alignment) {
+    if (Alignment == 0) Alignment = 1;
+    // Move the current buffer ptr up to the specified alignment.
+    CurBufferPtr =
+      (unsigned char*)(((intptr_t)CurBufferPtr+Alignment-1) & ~(Alignment-1));
+    void *Result = CurBufferPtr;
+    
+    // Allocate the space.
+    CurBufferPtr += Size;
+    
+    // Check for buffer overflow.
+    if (CurBufferPtr >= BufferEnd) {
+      CurBufferPtr = BufferEnd;
+      Result = 0;
+    }
+    return Result;
+  }
+  
+  
   /// getCurrentPCValue - This returns the address that the next emitted byte
   /// will be output to.
   ///