Convert a few enum constants to constexprs.

This eliminates some "bitwise operation between different enumeration
types" warnings in c++20, where such ops are deprecated.

Bug: chromium:1284275
Change-Id: Ie7f1d5e9430029bc694cef0358d217871670a8d3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3791964Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82057}

src/codegen/arm64/constants-arm64.h

@@ -468,53 +468,48 @@ enum SystemRegister {
 const uint32_t kUnallocatedInstruction = 0xffffffff;
 
 // Generic fields.
-enum GenericInstrField : uint32_t {
-  SixtyFourBits = 0x80000000,
-  ThirtyTwoBits = 0x00000000,
-  FP32 = 0x00000000,
-  FP64 = 0x00400000
-};
-
-enum NEONFormatField : uint32_t {
-  NEONFormatFieldMask = 0x40C00000,
-  NEON_Q = 0x40000000,
-  NEON_8B = 0x00000000,
-  NEON_16B = NEON_8B | NEON_Q,
-  NEON_4H = 0x00400000,
-  NEON_8H = NEON_4H | NEON_Q,
-  NEON_2S = 0x00800000,
-  NEON_4S = NEON_2S | NEON_Q,
-  NEON_1D = 0x00C00000,
-  NEON_2D = 0x00C00000 | NEON_Q
-};
-
-enum NEONFPFormatField : uint32_t {
-  NEONFPFormatFieldMask = 0x40400000,
-  NEON_FP_2S = FP32,
-  NEON_FP_4S = FP32 | NEON_Q,
-  NEON_FP_2D = FP64 | NEON_Q
-};
-
-enum NEONLSFormatField : uint32_t {
-  NEONLSFormatFieldMask = 0x40000C00,
-  LS_NEON_8B = 0x00000000,
-  LS_NEON_16B = LS_NEON_8B | NEON_Q,
-  LS_NEON_4H = 0x00000400,
-  LS_NEON_8H = LS_NEON_4H | NEON_Q,
-  LS_NEON_2S = 0x00000800,
-  LS_NEON_4S = LS_NEON_2S | NEON_Q,
-  LS_NEON_1D = 0x00000C00,
-  LS_NEON_2D = LS_NEON_1D | NEON_Q
-};
-
-enum NEONScalarFormatField : uint32_t {
-  NEONScalarFormatFieldMask = 0x00C00000,
-  NEONScalar = 0x10000000,
-  NEON_B = 0x00000000,
-  NEON_H = 0x00400000,
-  NEON_S = 0x00800000,
-  NEON_D = 0x00C00000
-};
+using GenericInstrField = uint32_t;
+constexpr GenericInstrField SixtyFourBits = 0x80000000;
+constexpr GenericInstrField ThirtyTwoBits = 0x00000000;
+constexpr GenericInstrField FP32 = 0x00000000;
+constexpr GenericInstrField FP64 = 0x00400000;
+
+using NEONFormatField = uint32_t;
+constexpr NEONFormatField NEONFormatFieldMask = 0x40C00000;
+constexpr NEONFormatField NEON_Q = 0x40000000;
+constexpr NEONFormatField NEON_8B = 0x00000000;
+constexpr NEONFormatField NEON_16B = NEON_8B | NEON_Q;
+constexpr NEONFormatField NEON_4H = 0x00400000;
+constexpr NEONFormatField NEON_8H = NEON_4H | NEON_Q;
+constexpr NEONFormatField NEON_2S = 0x00800000;
+constexpr NEONFormatField NEON_4S = NEON_2S | NEON_Q;
+constexpr NEONFormatField NEON_1D = 0x00C00000;
+constexpr NEONFormatField NEON_2D = 0x00C00000 | NEON_Q;
+
+using NEONFPFormatField = uint32_t;
+constexpr NEONFPFormatField NEONFPFormatFieldMask = 0x40400000;
+constexpr NEONFPFormatField NEON_FP_2S = FP32;
+constexpr NEONFPFormatField NEON_FP_4S = FP32 | NEON_Q;
+constexpr NEONFPFormatField NEON_FP_2D = FP64 | NEON_Q;
+
+using NEONLSFormatField = uint32_t;
+constexpr NEONLSFormatField NEONLSFormatFieldMask = 0x40000C00;
+constexpr NEONLSFormatField LS_NEON_8B = 0x00000000;
+constexpr NEONLSFormatField LS_NEON_16B = LS_NEON_8B | NEON_Q;
+constexpr NEONLSFormatField LS_NEON_4H = 0x00000400;
+constexpr NEONLSFormatField LS_NEON_8H = LS_NEON_4H | NEON_Q;
+constexpr NEONLSFormatField LS_NEON_2S = 0x00000800;
+constexpr NEONLSFormatField LS_NEON_4S = LS_NEON_2S | NEON_Q;
+constexpr NEONLSFormatField LS_NEON_1D = 0x00000C00;
+constexpr NEONLSFormatField LS_NEON_2D = LS_NEON_1D | NEON_Q;
+
+using NEONScalarFormatField = uint32_t;
+constexpr NEONScalarFormatField NEONScalarFormatFieldMask = 0x00C00000;
+constexpr NEONScalarFormatField NEONScalar = 0x10000000;
+constexpr NEONScalarFormatField NEON_B = 0x00000000;
+constexpr NEONScalarFormatField NEON_H = 0x00400000;
+constexpr NEONScalarFormatField NEON_S = 0x00800000;
+constexpr NEONScalarFormatField NEON_D = 0x00C00000;
 
 // PC relative addressing.
 enum PCRelAddressingOp : uint32_t {