BumpPtrAllocator: do the size check without moving any pointers

[oota-llvm.git] / include / llvm / Support / MathExtras.h

diff --git a/include/llvm/Support/MathExtras.h b/include/llvm/Support/MathExtras.h
index 0abba62a2c234850e68c8b8d7541f24f229839e8..6a104e738fa7919b0f83bf89c60c3c7d642c8400 100644 (file)
--- a/include/llvm/Support/MathExtras.h
+++ b/include/llvm/Support/MathExtras.h
@@ -550,16 +550,23 @@ inline uint64_t MinAlign(uint64_t A, uint64_t B) {
   return (A | B) & (1 + ~(A | B));
 }
 
-/// \brief Aligns \c Ptr to \c Alignment bytes, rounding up.
+/// \brief Aligns \c Addr to \c Alignment bytes, rounding up.
 ///
 /// Alignment should be a power of two.  This method rounds up, so
-/// AlignPtr(7, 4) == 8 and AlignPtr(8, 4) == 8.
-inline char *alignPtr(char *Ptr, size_t Alignment) {
+/// alignAddr(7, 4) == 8 and alignAddr(8, 4) == 8.
+inline uintptr_t alignAddr(void *Addr, size_t Alignment) {
   assert(Alignment && isPowerOf2_64((uint64_t)Alignment) &&
          "Alignment is not a power of two!");
 
-  return (char *)(((uintptr_t)Ptr + Alignment - 1) &
-                  ~(uintptr_t)(Alignment - 1));
+  assert((uintptr_t)Addr + Alignment - 1 >= (uintptr_t)Addr);
+
+  return (((uintptr_t)Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1));
+}
+
+/// \brief Returns the necessary adjustment for aligning \c Ptr to \c Alignment
+/// bytes, rounding up.
+inline size_t alignmentAdjustment(void *Ptr, size_t Alignment) {
+  return alignAddr(Ptr, Alignment) - (uintptr_t)Ptr;
 }
 
 /// NextPowerOf2 - Returns the next power of two (in 64-bits)