[PATCH] D25344: Add a fast path to alignTo.

[Rui Ueyama via llvm-commits]

ruiu created this revision.
ruiu added reviewers: rafael, davide.
ruiu added a subscriber: llvm-commits.

If an alignment is a power of two, we can avoid integer division,
and it is very likely to happen.


https://reviews.llvm.org/D25344

Files:
  include/llvm/Support/MathExtras.h


Index: include/llvm/Support/MathExtras.h
===================================================================
--- include/llvm/Support/MathExtras.h
+++ include/llvm/Support/MathExtras.h
@@ -670,6 +670,10 @@
 /// \endcode
 inline uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew = 0) {
   assert(Align != 0u && "Align can't be 0.");
+  if (LLVM_LIKELY(isPowerOf2_64(Align))) {
+    Skew &= Align - 1;
+    return ((Value + Align - 1 - Skew) & -Align) + Skew;
+  }
   Skew %= Align;
   return (Value + Align - 1 - Skew) / Align * Align + Skew;
 }


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