[Alignment][NFC] Add a helper function to DataLayout

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

Reviewers: courbet

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69258

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375413 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/DataLayout.h

@@ -504,6 +504,13 @@ class DataLayout {
   /// Returns the minimum ABI-required alignment for the specified type.
   unsigned getABITypeAlignment(Type *Ty) const;
 
+  /// Helper function to return `Alignment` if it's set or the result of
+  /// `getABITypeAlignment(Ty)`, in any case the result is a valid alignment.
+  inline Align getValueOrABITypeAlignment(MaybeAlign Alignment,
+                                          Type *Ty) const {
+    return Alignment ? *Alignment : Align(getABITypeAlignment(Ty));
+  }
+
   /// Returns the minimum ABI-required alignment for an integer type of
   /// the specified bitwidth.
   Align getABIIntegerTypeAlignment(unsigned BitWidth) const;

unittests/IR/DataLayoutTest.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Type.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -44,4 +46,14 @@ TEST(DataLayoutTest, FunctionPtrAlign) {
   EXPECT_EQ(a, c);
 }
 
+TEST(DataLayoutTest, ValueOrABITypeAlignment) {
+  const DataLayout DL("Fi8");
+  LLVMContext Context;
+  Type *const FourByteAlignType = Type::getInt32Ty(Context);
+  EXPECT_EQ(Align(16),
+            DL.getValueOrABITypeAlignment(MaybeAlign(16), FourByteAlignType));
+  EXPECT_EQ(Align(4),
+            DL.getValueOrABITypeAlignment(MaybeAlign(), FourByteAlignType));
+}
+
 }  // anonymous namespace