[llvm] r286549 - [ADT/MathExtras] Introduce PowerOf2Ceil.

[Davide Italiano via llvm-commits]

Author: davide
Date: Thu Nov 10 20:22:16 2016
New Revision: 286549

URL: http://llvm.org/viewvc/llvm-project?rev=286549&view=rev
Log:
[ADT/MathExtras] Introduce PowerOf2Ceil.

To be used in lld (and probably somewhere else in llvm).

Differential Revision:  https://reviews.llvm.org/D26538

Modified:
    llvm/trunk/include/llvm/Support/MathExtras.h
    llvm/trunk/unittests/Support/MathExtrasTest.cpp

Modified: llvm/trunk/include/llvm/Support/MathExtras.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MathExtras.h?rev=286549&r1=286548&r2=286549&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MathExtras.h (original)
+++ llvm/trunk/include/llvm/Support/MathExtras.h Thu Nov 10 20:22:16 2016
@@ -641,6 +641,14 @@ inline uint64_t PowerOf2Floor(uint64_t A
   return 1ull << (63 - countLeadingZeros(A, ZB_Undefined));
 }
 
+/// Returns the power of two which is greater than or equal to the given value.
+/// Essentially, it is a ceil operation across the domain of powers of two.
+inline uint64_t PowerOf2Ceil(uint64_t A) {
+  if (!A)
+    return 0;
+  return NextPowerOf2(A - 1);
+}
+
 /// Returns the next integer (mod 2**64) that is greater than or equal to
 /// \p Value and is a multiple of \p Align. \p Align must be non-zero.
 ///

Modified: llvm/trunk/unittests/Support/MathExtrasTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/MathExtrasTest.cpp?rev=286549&r1=286548&r2=286549&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/MathExtrasTest.cpp (original)
+++ llvm/trunk/unittests/Support/MathExtrasTest.cpp Thu Nov 10 20:22:16 2016
@@ -165,6 +165,12 @@ TEST(MathExtras, isPowerOf2_64) {
   EXPECT_FALSE(isPowerOf2_64(0xABCDEF0ABCDEF0LL));
 }
 
+TEST(MathExtras, PowerOf2Ceil) {
+  EXPECT_EQ(0, PowerOf2Ceil(0));
+  EXPECT_EQ(8, PowerOf2Ceil(8));
+  EXPECT_EQ(8, PowerOf2Ceil(7));
+}
+
 TEST(MathExtras, ByteSwap_32) {
   EXPECT_EQ(0x44332211u, ByteSwap_32(0x11223344));
   EXPECT_EQ(0xDDCCBBAAu, ByteSwap_32(0xAABBCCDD));