[ptr-compr] Switch to 31 bit Smis on 64-bit architectures

32 bit Smis are incompatible with pointer compression so we land disable
them before enabling pointer compression in order to separate memory and
performance regressions caused by 31 bit Smis from pointer compression
change.

Bug: v8:9767
Change-Id: I3d4a675df4208f808b1ba6e7816be545eae0dc24
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1815249Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63934}

BUILD.gn

@@ -108,7 +108,7 @@ declare_args() {
 
   # Enable pointer compression (sets -dV8_COMPRESS_POINTERS).
   v8_enable_pointer_compression = false
-  v8_enable_31bit_smis_on_64bit_arch = false
+  v8_enable_31bit_smis_on_64bit_arch = true
 
   # Sets -dOBJECT_PRINT.
   v8_enable_object_print = ""

src/codegen/code-stub-assembler.cc

@@ -1146,7 +1146,7 @@ TNode<BoolT> CodeStubAssembler::TaggedIsPositiveSmi(SloppyTNode<Object> a) {
   return Word32Equal(
       Word32And(
           TruncateIntPtrToInt32(BitcastTaggedToWordForTagAndSmiBits(a)),
-          Uint32Constant(kSmiTagMask | static_cast<int32_t>(kSmiSignMask))),
+          Uint32Constant(static_cast<uint32_t>(kSmiTagMask | kSmiSignMask))),
       Int32Constant(0));
 #else
   return WordEqual(WordAnd(BitcastTaggedToWordForTagAndSmiBits(a),