[PATCH] D47024: [MathExtras] Add alignToPowerOf2

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: jlebar, ruiu.
Herald added a subscriber: llvm-commits.

When Align is a variable known to be a power of 2, this can be faster than alignTo by replacing a div instruction with bitwise operation.


Repository:
  rL LLVM

https://reviews.llvm.org/D47024

Files:
  include/llvm/Support/MathExtras.h


Index: include/llvm/Support/MathExtras.h
===================================================================
--- include/llvm/Support/MathExtras.h
+++ include/llvm/Support/MathExtras.h
@@ -687,6 +687,12 @@
   return (Value + Align - 1) / Align * Align;
 }
 
+inline uint64_t alignToPowerOf2(uint64_t Value, uint64_t Align) {
+  assert(Align != 0 && (Align & Align - 1) == 0 &&
+         "Align must be a power of 2");
+  return (Value + Align - 1) & -Align;
+}
+
 /// Returns the integer ceil(Numerator / Denominator).
 inline uint64_t divideCeil(uint64_t Numerator, uint64_t Denominator) {
   return alignTo(Numerator, Denominator) / Denominator;


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