Enable 31bit Smis everywhere

This is a experiment to see how performance is impacted. If we tank
too much, we can revert this change.

Change-Id: I01be33f5dd78aee6a5beecdc62adbaa6c3850eb1
Bug: v8:8344
Reviewed-on: https://chromium-review.googlesource.com/c/1355279
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58157}

BUILD.gn

@@ -98,7 +98,6 @@ declare_args() {
 
   # Enable pointer compression (sets -dV8_COMPRESS_POINTERS).
   v8_enable_pointer_compression = false
-  v8_enable_31bit_smis_on_64bit_arch = false
 
   # Interpreted regexp engine exists as platform-independent alternative
   # based where the regular expression is compiled to a bytecode.
@@ -344,9 +343,6 @@ config("features") {
   if (v8_enable_pointer_compression) {
     defines += [ "V8_COMPRESS_POINTERS" ]
   }
-  if (v8_enable_31bit_smis_on_64bit_arch) {
-    defines += [ "V8_31BIT_SMIS_ON_64BIT_ARCH" ]
-  }
   if (v8_enable_object_print) {
     defines += [ "OBJECT_PRINT" ]
   }

include/v8-internal.h

@@ -92,11 +92,7 @@ static_assert(
     "Pointer compression can be enabled only for 64-bit architectures");
 #endif
 
-#if defined(V8_COMPRESS_POINTERS) || defined(V8_31BIT_SMIS_ON_64BIT_ARCH)
 typedef SmiTagging<kApiIntSize> PlatformSmiTagging;
-#else
-typedef SmiTagging<kApiSystemPointerSize> PlatformSmiTagging;
-#endif
 
 const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize;
 const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize;