[llvm] Use conventional enum declarations (NFC) (#166318)

This patch replaces:

  using Foo = enum { A, B, C };

with the more conventional:

  enum Foo { A, B, C };

These two enum declaration styles are not identical, but their
difference does not matter in these .cpp files.  With the "using Foo"
style, the enum is unnamed and cannot be forward-declared, whereas the
conventional style creates a named enum that can be.  Since these
changes are confined to .cpp files, this distinction has no practical
impact here.

Author: kazutakahirata

llvm/lib/Target/AArch64/AArch64FastISel.cpp

@@ -81,10 +81,7 @@ namespace {
 class AArch64FastISel final : public FastISel {
   class Address {
   public:
-    using BaseKind = enum {
-      RegBase,
-      FrameIndexBase
-    };
+    enum BaseKind { RegBase, FrameIndexBase };
 
   private:
     BaseKind Kind = RegBase;

llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp

@@ -435,7 +435,7 @@ void GCNHazardRecognizer::RecedeCycle() {
 // Helper Functions
 //===----------------------------------------------------------------------===//
 
-using HazardFnResult = enum { HazardFound, HazardExpired, NoHazardFound };
+enum HazardFnResult { HazardFound, HazardExpired, NoHazardFound };
 
 using IsExpiredFn = function_ref<bool(const MachineInstr &, int WaitStates)>;
 using GetNumWaitStatesFn = function_ref<unsigned int(const MachineInstr &)>;

llvm/lib/Target/AMDGPU/GCNNSAReassign.cpp

@@ -43,7 +43,7 @@ class GCNNSAReassignImpl {
   bool run(MachineFunction &MF);
 
 private:
-  using NSA_Status = enum {
+  enum NSA_Status {
     NOT_NSA,        // Not an NSA instruction
     FIXED,          // NSA which we cannot modify
     NON_CONTIGUOUS, // NSA with non-sequential address which we can try

llvm/lib/Target/ARM/ARMFastISel.cpp

@@ -86,7 +86,7 @@ namespace {
   // All possible address modes, plus some.
 class Address {
 public:
-  using BaseKind = enum { RegBase, FrameIndexBase };
+  enum BaseKind { RegBase, FrameIndexBase };
 
 private:
   BaseKind Kind = RegBase;

llvm/lib/Target/Mips/MipsFastISel.cpp

@@ -82,7 +82,7 @@ class MipsFastISel final : public FastISel {
   // All possible address modes.
   class Address {
   public:
-    using BaseKind = enum { RegBase, FrameIndexBase };
+    enum BaseKind { RegBase, FrameIndexBase };
 
   private:
     BaseKind Kind = RegBase;

llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp

@@ -46,7 +46,7 @@ class WebAssemblyFastISel final : public FastISel {
   // All possible address modes.
   class Address {
   public:
-    using BaseKind = enum { RegBase, FrameIndexBase };
+    enum BaseKind { RegBase, FrameIndexBase };
 
   private:
     BaseKind Kind = RegBase;

llvm/lib/Target/X86/X86VZeroUpper.cpp

@@ -66,7 +66,7 @@ namespace {
                           MachineBasicBlock &MBB);
     void addDirtySuccessor(MachineBasicBlock &MBB);
 
-    using BlockExitState = enum { PASS_THROUGH, EXITS_CLEAN, EXITS_DIRTY };
+    enum BlockExitState { PASS_THROUGH, EXITS_CLEAN, EXITS_DIRTY };
 
     static const char* getBlockExitStateName(BlockExitState ST);
 

llvm/unittests/ADT/FallibleIteratorTest.cpp

@@ -19,8 +19,8 @@ using namespace llvm;
 
 namespace {
 
-using ItemValid = enum { ValidItem, InvalidItem };
-using LinkValid = enum { ValidLink, InvalidLink };
+enum ItemValid { ValidItem, InvalidItem };
+enum LinkValid { ValidLink, InvalidLink };
 
 class Item {
 public: