[AMDGPU] Use std::array in GCNRegPressure (NFC) (#164117)

With std::array, we can simplify clear and operator==.

Author: kazutakahirata

llvm/lib/Target/AMDGPU/GCNRegPressure.h

@@ -21,6 +21,7 @@
 #include "llvm/CodeGen/LiveIntervals.h"
 #include "llvm/CodeGen/RegisterPressure.h"
 #include <algorithm>
+#include <array>
 
 namespace llvm {
 
@@ -45,7 +46,7 @@ struct GCNRegPressure {
     return !Value[SGPR] && !Value[VGPR] && !Value[AGPR] && !Value[AVGPR];
   }
 
-  void clear() { std::fill(&Value[0], &Value[ValueArraySize], 0); }
+  void clear() { Value.fill(0); }
 
   unsigned getNumRegs(RegKind Kind) const {
     assert(Kind < TOTAL_KINDS);
@@ -127,9 +128,7 @@ struct GCNRegPressure {
   bool less(const MachineFunction &MF, const GCNRegPressure &O,
             unsigned MaxOccupancy = std::numeric_limits<unsigned>::max()) const;
 
-  bool operator==(const GCNRegPressure &O) const {
-    return std::equal(&Value[0], &Value[ValueArraySize], O.Value);
-  }
+  bool operator==(const GCNRegPressure &O) const { return Value == O.Value; }
 
   bool operator!=(const GCNRegPressure &O) const {
     return !(*this == O);
@@ -160,7 +159,7 @@ struct GCNRegPressure {
 
   /// Pressure for all register kinds (first all regular registers kinds, then
   /// all tuple register kinds).
-  unsigned Value[ValueArraySize];
+  std::array<unsigned, ValueArraySize> Value;
 
   static unsigned getRegKind(const TargetRegisterClass *RC,
                              const SIRegisterInfo *STI);