[Alignment][NFC] Adding a max function.

[gchatelet]

Summary

This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

[courbet]

llvm/unittests/Support/AlignmentTest.cpp

241

Maybe add tests for max(Align, Align) to make sure ADL resolves as expected.

[gchatelet]

• Address comments

[gchatelet]

Thx!

llvm/include/llvm/Support/Alignment.h

 }
 
 inline MaybeAlign operator/(MaybeAlign Lhs, uint64_t Divisor) {
   assert(llvm::isPowerOf2_64(Divisor) &&
          "Divisor must be positive and a power of 2");
   return Lhs ? Lhs.getValue() / Divisor : MaybeAlign();
 }
 
+inline Align max(MaybeAlign Lhs, Align Rhs) {
+  return Lhs && *Lhs > Rhs ? *Lhs : Rhs;
+}
+
+inline Align max(Align Lhs, MaybeAlign Rhs) {
+  return Rhs && *Rhs > Lhs ? *Rhs : Lhs;
+}
+
 #undef ALIGN_CHECK_ISPOSITIVE
 #undef ALIGN_CHECK_ISSET
 
 } // namespace llvm
 
 #endif // LLVM_SUPPORT_ALIGNMENT_H_

llvm/unittests/Support/AlignmentTest.cpp

for (size_t I = 1; I < ValidAlignments.size(); ++I) {
     EXPECT_LE(MA, MA ? (*MA).value() : 0);
     EXPECT_GE(MA, MA ? (*MA).value() : 0);
 
     EXPECT_EQ(std::max(A, B), B);
     EXPECT_EQ(std::min(A, B), A);
   }
 }
 
+TEST(AlignmentTest, Max) {
+  // We introduce std::max here to test ADL.
+  using std::max;
+
+  // Uses llvm::max.
+  EXPECT_EQ(max(MaybeAlign(), Align(2)), Align(2));
+  EXPECT_EQ(max(Align(2), MaybeAlign()), Align(2));
+
+  EXPECT_EQ(max(MaybeAlign(1), Align(2)), Align(2));
+  EXPECT_EQ(max(Align(2), MaybeAlign(1)), Align(2));
+
+  EXPECT_EQ(max(MaybeAlign(2), Align(2)), Align(2));
+  EXPECT_EQ(max(Align(2), MaybeAlign(2)), Align(2));
+
+  EXPECT_EQ(max(MaybeAlign(4), Align(2)), Align(4));
+  EXPECT_EQ(max(Align(2), MaybeAlign(4)), Align(4));
+
+  // Uses std::max.
+  EXPECT_EQ(max(Align(2), Align(4)), Align(4));
+  EXPECT_EQ(max(MaybeAlign(2), MaybeAlign(4)), MaybeAlign(4));
+  EXPECT_EQ(max(MaybeAlign(), MaybeAlign()), MaybeAlign());
+}
+
 TEST(AlignmentTest, AssumeAligned) {
   EXPECT_EQ(assumeAligned(0), Align(1));
   EXPECT_EQ(assumeAligned(0), Align());
   EXPECT_EQ(assumeAligned(1), Align(1));
   EXPECT_EQ(assumeAligned(1), Align());
 }
 
 // Death tests reply on assert which is disabled in release mode.