[ptr-compr][arm64] Implementing SmiUntagField which loads a field

containing smi value and untags it.

This CL finishes up the parity with x64 with regards to
(https://chromium-review.googlesource.com/c/v8/v8/+/1382740)

Bug: v8:7703
Change-Id: I3c88fbbfd3e47e944a6891171d6555f330cd5fd2
Reviewed-on: https://chromium-review.googlesource.com/c/1463523Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59521}

src/arm64/macro-assembler-arm64.cc

@@ -2762,6 +2762,10 @@ void TurboAssembler::LoadAnyTaggedField(const Register& destination,
 #endif
 }
 
+void TurboAssembler::SmiUntagField(Register dst, const MemOperand& src) {
+  SmiUntag(dst, src);
+}
+
 void TurboAssembler::StoreTaggedField(const Register& value,
                                       const MemOperand& dst_field_operand) {
   Str(value, dst_field_operand);

src/arm64/macro-assembler-arm64.h

@@ -1187,6 +1187,9 @@ class V8_EXPORT_PRIVATE TurboAssembler : public TurboAssemblerBase {
   void LoadAnyTaggedField(const Register& destination,
                           const MemOperand& field_operand);
 
+  // Loads a field containing smi value and untags it.
+  void SmiUntagField(Register dst, const MemOperand& src);
+
   // Compresses and stores tagged value to given on-heap location.
   void StoreTaggedField(const Register& value,
                         const MemOperand& dst_field_operand);

src/builtins/arm64/builtins-arm64.cc

@@ -1780,8 +1780,8 @@ void Builtins::Generate_InterpreterOnStackReplacement(MacroAssembler* masm) {
 
   // Load the OSR entrypoint offset from the deoptimization data.
   // <osr_offset> = <deopt_data>[#header_size + #osr_pc_offset]
-  __ SmiUntag(x1,
-              FieldMemOperand(x1, FixedArray::OffsetOfElementAt(
+  __ SmiUntagField(
+      x1, FieldMemOperand(x1, FixedArray::OffsetOfElementAt(
                                   DeoptimizationData::kOsrPcOffsetIndex)));
 
   // Compute the target address = code_obj + header_size + osr_offset
@@ -2467,7 +2467,7 @@ void Generate_PushBoundArguments(MacroAssembler* masm) {
   Label no_bound_arguments;
   __ LoadTaggedPointerField(
       bound_argv, FieldMemOperand(x1, JSBoundFunction::kBoundArgumentsOffset));
-  __ SmiUntag(bound_argc,
+  __ SmiUntagField(bound_argc,
                    FieldMemOperand(bound_argv, FixedArray::kLengthOffset));
   __ Cbz(bound_argc, &no_bound_arguments);
   {