[LLVM][Alignment] Introduce Alignment In GlobalObject

Summary:
This is patch is part of a serie 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: jfb

Subscribers: hiraditya, dexonsmith, llvm-commits, courbet

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65748

Address comments

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368000 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/GlobalObject.h

@@ -17,6 +17,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/Value.h"
+#include "llvm/Support/Alignment.h"
 #include <string>
 #include <utility>
 
@@ -58,9 +59,13 @@ public:
   unsigned getAlignment() const {
     unsigned Data = getGlobalValueSubClassData();
     unsigned AlignmentData = Data & AlignmentMask;
-    return (1u << AlignmentData) >> 1;
+    MaybeAlign Align = decodeMaybeAlign(AlignmentData);
+    return Align ? Align->value() : 0;
   }
+
+  /// FIXME: Remove this setter once the migration to MaybeAlign is over.
   void setAlignment(unsigned Align);
+  void setAlignment(MaybeAlign Align);
 
   unsigned getGlobalObjectSubClassData() const {
     unsigned ValueData = getGlobalValueSubClassData();

include/llvm/Support/Alignment.h

@@ -101,7 +101,7 @@ public:
 
   explicit MaybeAlign(uint64_t Value) {
     assert((Value == 0 || llvm::isPowerOf2_64(Value)) &&
-           "Alignment is not 0 or a power of 2");
+           "Alignment is neither 0 nor a power of 2");
     if (Value)
       emplace(Value);
   }

lib/IR/Globals.cpp

@@ -114,13 +114,17 @@ unsigned GlobalValue::getAddressSpace() const {
 }
 
 void GlobalObject::setAlignment(unsigned Align) {
-  assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!");
-  assert(Align <= MaximumAlignment &&
-         "Alignment is greater than MaximumAlignment!");
-  unsigned AlignmentData = Log2_32(Align) + 1;
+  setAlignment(MaybeAlign(Align));
+}
+
+void GlobalObject::setAlignment(MaybeAlign Align) {
+  assert(!Align || Align <= MaximumAlignment &&
+                       "Alignment is greater than MaximumAlignment!");
+  unsigned AlignmentData = encode(Align);
   unsigned OldData = getGlobalValueSubClassData();
   setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData);
-  assert(getAlignment() == Align && "Alignment representation error!");
+  assert(MaybeAlign(getAlignment()) == Align &&
+         "Alignment representation error!");
 }
 
 void GlobalObject::copyAttributesFrom(const GlobalObject *Src) {

unittests/IR/ValueTest.cpp

@@ -99,7 +99,8 @@ TEST(GlobalTest, AlignDeath) {
                          Constant::getAllOnesValue(Int32Ty), "var", nullptr,
                          GlobalVariable::NotThreadLocal, 1);
 
-  EXPECT_DEATH(Var->setAlignment(536870913U), "Alignment is not a power of 2");
+  EXPECT_DEATH(Var->setAlignment(536870913U),
+               "Alignment is neither 0 nor a power of 2");
   EXPECT_DEATH(Var->setAlignment(1073741824U),
                "Alignment is greater than MaximumAlignment");
 }

unittests/Support/AlignmentTest.cpp

@@ -256,7 +256,8 @@ TEST(AlignmentDeathTest, InvalidCTors) {
   EXPECT_DEATH((Align(0)), "Value must not be 0");
   for (uint64_t Value : getNonPowerOfTwo()) {
     EXPECT_DEATH((Align(Value)), "Alignment is not a power of 2");
-    EXPECT_DEATH((MaybeAlign(Value)), "Alignment is not 0 or a power of 2");
+    EXPECT_DEATH((MaybeAlign(Value)),
+                 "Alignment is neither 0 nor a power of 2");
   }
 }