diff --git a/src/arm64/assembler-arm64-inl.h b/src/arm64/assembler-arm64-inl.h
index 444f2c4a94..a0bcb77e6b 100644
--- a/src/arm64/assembler-arm64-inl.h
+++ b/src/arm64/assembler-arm64-inl.h
@@ -430,12 +430,16 @@ unsigned Operand::shift_amount() const {
 
 
 Operand Operand::UntagSmi(Register smi) {
+  STATIC_ASSERT(kXRegSizeInBits == static_cast<unsigned>(kSmiShift +
+                                                         kSmiValueSize));
   ASSERT(smi.Is64Bits());
   return Operand(smi, ASR, kSmiShift);
 }
 
 
 Operand Operand::UntagSmiAndScale(Register smi, int scale) {
+  STATIC_ASSERT(kXRegSizeInBits == static_cast<unsigned>(kSmiShift +
+                                                         kSmiValueSize));
   ASSERT(smi.Is64Bits());
   ASSERT((scale >= 0) && (scale <= (64 - kSmiValueSize)));
   if (scale > kSmiShift) {
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index 31b61f479d..9c5e3e9045 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -1246,7 +1246,7 @@ void Builtins::Generate_FunctionApply(MacroAssembler* masm) {
     // TODO(jbramley): Check that the stack usage here is safe.
     __ Sub(x10, jssp, x10);
     // Check if the arguments will overflow the stack.
-    __ Cmp(x10, Operand(argc, LSR, kSmiShift - kPointerSizeLog2));
+    __ Cmp(x10, Operand::UntagSmiAndScale(argc, kPointerSizeLog2));
     __ B(gt, &enough_stack_space);
     // There is not enough stack space, so use a builtin to throw an appropriate
     // error.
diff --git a/src/arm64/code-stubs-arm64.cc b/src/arm64/code-stubs-arm64.cc
index 0e08907061..e24c7bd078 100644
--- a/src/arm64/code-stubs-arm64.cc
+++ b/src/arm64/code-stubs-arm64.cc
@@ -1988,9 +1988,8 @@ void ArgumentsAccessStub::GenerateNewSloppySlow(MacroAssembler* masm) {
   Register caller_fp = x10;
   __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
   // Load and untag the context.
-  STATIC_ASSERT((kSmiShift / kBitsPerByte) == 4);
-  __ Ldr(w11, MemOperand(caller_fp, StandardFrameConstants::kContextOffset +
-                         (kSmiShift / kBitsPerByte)));
+  __ Ldr(w11, UntagSmiMemOperand(caller_fp,
+                                 StandardFrameConstants::kContextOffset));
   __ Cmp(w11, StackFrame::ARGUMENTS_ADAPTOR);
   __ B(ne, &runtime);
 
@@ -2838,8 +2837,8 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // Store the smi values in the last match info.
   __ SmiTag(x10, current_offset);
   // Clearing the 32 bottom bits gives us a Smi.
-  STATIC_ASSERT(kSmiShift == 32);
-  __ And(x11, current_offset, ~kWRegMask);
+  STATIC_ASSERT(kSmiTag == 0);
+  __ Bic(x11, current_offset, kSmiShiftMask);
   __ Stp(x10,
          x11,
          MemOperand(last_match_offsets, kXRegSize * 2, PostIndex));
@@ -3478,8 +3477,7 @@ void StringCharFromCodeGenerator::GenerateFast(MacroAssembler* masm) {
 
   __ LoadRoot(result_, Heap::kSingleCharacterStringCacheRootIndex);
   // At this point code register contains smi tagged ASCII char code.
-  STATIC_ASSERT(kSmiShift > kPointerSizeLog2);
-  __ Add(result_, result_, Operand(code_, LSR, kSmiShift - kPointerSizeLog2));
+  __ Add(result_, result_, Operand::UntagSmiAndScale(code_, kPointerSizeLog2));
   __ Ldr(result_, FieldMemOperand(result_, FixedArray::kHeaderSize));
   __ JumpIfRoot(result_, Heap::kUndefinedValueRootIndex, &slow_case_);
   __ Bind(&exit_);
@@ -3848,7 +3846,7 @@ void StringHelper::GenerateHashInit(MacroAssembler* masm,
   // hash = character + (character << 10);
   __ LoadRoot(hash, Heap::kHashSeedRootIndex);
   // Untag smi seed and add the character.
-  __ Add(hash, character, Operand(hash, LSR, kSmiShift));
+  __ Add(hash, character, Operand::UntagSmi(hash));
 
   // Compute hashes modulo 2^32 using a 32-bit W register.
   Register hash_w = hash.W();
diff --git a/src/arm64/debug-arm64.cc b/src/arm64/debug-arm64.cc
index 43684d5157..1578452138 100644
--- a/src/arm64/debug-arm64.cc
+++ b/src/arm64/debug-arm64.cc
@@ -171,7 +171,8 @@ static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
       //  jssp[8]: 0x00000000 (SMI tag & padding)
       //  jssp[4]: reg[31:0]
       //  jssp[0]: 0x00000000 (SMI tag & padding)
-      STATIC_ASSERT((kSmiTag == 0) && (kSmiShift == 32));
+      STATIC_ASSERT(kSmiTag == 0);
+      STATIC_ASSERT(static_cast<unsigned>(kSmiShift) == kWRegSizeInBits);
     }
 
     if (object_regs != 0) {
diff --git a/src/arm64/full-codegen-arm64.cc b/src/arm64/full-codegen-arm64.cc
index afd5f72988..f027dc68a4 100644
--- a/src/arm64/full-codegen-arm64.cc
+++ b/src/arm64/full-codegen-arm64.cc
@@ -2029,11 +2029,12 @@ void FullCodeGenerator::EmitInlineSmiBinaryOp(BinaryOperation* expr,
       break;
     case Token::MUL: {
       Label not_minus_zero, done;
+      STATIC_ASSERT(static_cast<unsigned>(kSmiShift) == (kXRegSizeInBits / 2));
+      STATIC_ASSERT(kSmiTag == 0);
       __ Smulh(x10, left, right);
       __ Cbnz(x10, &not_minus_zero);
       __ Eor(x11, left, right);
       __ Tbnz(x11, kXSignBit, &stub_call);
-      STATIC_ASSERT(kSmiTag == 0);
       __ Mov(result, x10);
       __ B(&done);
       __ Bind(&not_minus_zero);
@@ -2592,9 +2593,10 @@ void FullCodeGenerator::EmitIsNonNegativeSmi(CallRuntime* expr) {
   context()->PrepareTest(&materialize_true, &materialize_false,
                          &if_true, &if_false, &fall_through);
 
+  uint64_t sign_mask = V8_UINT64_C(1) << (kSmiShift + kSmiValueSize - 1);
+
   PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
-  __ TestAndSplit(x0, kSmiTagMask | (0x80000000UL << kSmiShift), if_true,
-                  if_false, fall_through);
+  __ TestAndSplit(x0, kSmiTagMask | sign_mask, if_true, if_false, fall_through);
 
   context()->Plug(if_true, if_false);
 }
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index ed6fde31af..dd24b9c65e 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -3525,7 +3525,8 @@ MemOperand LCodeGen::PrepareKeyedArrayOperand(Register base,
                                               ElementsKind elements_kind,
                                               Representation representation,
                                               int base_offset) {
-  STATIC_ASSERT((kSmiValueSize == 32) && (kSmiShift == 32) && (kSmiTag == 0));
+  STATIC_ASSERT(static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits);
+  STATIC_ASSERT(kSmiTag == 0);
   int element_size_shift = ElementsKindToShiftSize(elements_kind);
 
   // Even though the HLoad/StoreKeyed instructions force the input
@@ -3536,8 +3537,7 @@ MemOperand LCodeGen::PrepareKeyedArrayOperand(Register base,
     __ Add(base, elements, Operand::UntagSmiAndScale(key, element_size_shift));
     if (representation.IsInteger32()) {
       ASSERT(elements_kind == FAST_SMI_ELEMENTS);
-      // Read or write only the most-significant 32 bits in the case of fast smi
-      // arrays.
+      // Read or write only the smi payload in the case of fast smi arrays.
       return UntagSmiMemOperand(base, base_offset);
     } else {
       return MemOperand(base, base_offset);
@@ -3548,8 +3548,7 @@ MemOperand LCodeGen::PrepareKeyedArrayOperand(Register base,
     ASSERT((element_size_shift >= 0) && (element_size_shift <= 4));
     if (representation.IsInteger32()) {
       ASSERT(elements_kind == FAST_SMI_ELEMENTS);
-      // Read or write only the most-significant 32 bits in the case of fast smi
-      // arrays.
+      // Read or write only the smi payload in the case of fast smi arrays.
       __ Add(base, elements, Operand(key, SXTW, element_size_shift));
       return UntagSmiMemOperand(base, base_offset);
     } else {
@@ -3612,8 +3611,8 @@ void LCodeGen::DoLoadKeyedFixed(LLoadKeyedFixed* instr) {
         ToInteger32(const_operand) * kPointerSize;
     if (representation.IsInteger32()) {
       ASSERT(instr->hydrogen()->elements_kind() == FAST_SMI_ELEMENTS);
-      STATIC_ASSERT((kSmiValueSize == 32) && (kSmiShift == 32) &&
-                    (kSmiTag == 0));
+      STATIC_ASSERT(static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits);
+      STATIC_ASSERT(kSmiTag == 0);
       mem_op = UntagSmiMemOperand(elements, offset);
     } else {
       mem_op = MemOperand(elements, offset);
@@ -3683,7 +3682,8 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   if (access.representation().IsSmi() &&
       instr->hydrogen()->representation().IsInteger32()) {
     // Read int value directly from upper half of the smi.
-    STATIC_ASSERT(kSmiValueSize == 32 && kSmiShift == 32 && kSmiTag == 0);
+    STATIC_ASSERT(static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits);
+    STATIC_ASSERT(kSmiTag == 0);
     __ Load(result, UntagSmiFieldMemOperand(source, offset),
             Representation::Integer32());
   } else {
@@ -5286,8 +5286,8 @@ void LCodeGen::DoStoreKeyedFixed(LStoreKeyedFixed* instr) {
     if (representation.IsInteger32()) {
       ASSERT(instr->hydrogen()->store_mode() == STORE_TO_INITIALIZED_ENTRY);
       ASSERT(instr->hydrogen()->elements_kind() == FAST_SMI_ELEMENTS);
-      STATIC_ASSERT((kSmiValueSize == 32) && (kSmiShift == 32) &&
-                    (kSmiTag == 0));
+      STATIC_ASSERT(static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits);
+      STATIC_ASSERT(kSmiTag == 0);
       mem_op = UntagSmiMemOperand(store_base, offset);
     } else {
       mem_op = MemOperand(store_base, offset);
@@ -5406,7 +5406,8 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
       __ Ldr(destination, FieldMemOperand(object, JSObject::kPropertiesOffset));
     }
 #endif
-    STATIC_ASSERT(kSmiValueSize == 32 && kSmiShift == 32 && kSmiTag == 0);
+    STATIC_ASSERT(static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits);
+    STATIC_ASSERT(kSmiTag == 0);
     __ Store(value, UntagSmiFieldMemOperand(destination, offset),
              Representation::Integer32());
   } else {
diff --git a/src/arm64/macro-assembler-arm64-inl.h b/src/arm64/macro-assembler-arm64-inl.h
index 3ce4855b8a..4a93053811 100644
--- a/src/arm64/macro-assembler-arm64-inl.h
+++ b/src/arm64/macro-assembler-arm64-inl.h
@@ -1308,6 +1308,8 @@ void MacroAssembler::InitializeRootRegister() {
 
 
 void MacroAssembler::SmiTag(Register dst, Register src) {
+  STATIC_ASSERT(kXRegSizeInBits ==
+                static_cast<unsigned>(kSmiShift + kSmiValueSize));
   ASSERT(dst.Is64Bits() && src.Is64Bits());
   Lsl(dst, src, kSmiShift);
 }
@@ -1317,6 +1319,8 @@ void MacroAssembler::SmiTag(Register smi) { SmiTag(smi, smi); }
 
 
 void MacroAssembler::SmiUntag(Register dst, Register src) {
+  STATIC_ASSERT(kXRegSizeInBits ==
+                static_cast<unsigned>(kSmiShift + kSmiValueSize));
   ASSERT(dst.Is64Bits() && src.Is64Bits());
   if (FLAG_enable_slow_asserts) {
     AssertSmi(src);
@@ -1351,13 +1355,17 @@ void MacroAssembler::SmiUntagToFloat(FPRegister dst,
 
 
 void MacroAssembler::SmiTagAndPush(Register src) {
-  STATIC_ASSERT((kSmiShift == 32) && (kSmiTag == 0));
+  STATIC_ASSERT((static_cast<unsigned>(kSmiShift) == kWRegSizeInBits) &&
+                (static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits) &&
+                (kSmiTag == 0));
   Push(src.W(), wzr);
 }
 
 
 void MacroAssembler::SmiTagAndPush(Register src1, Register src2) {
-  STATIC_ASSERT((kSmiShift == 32) && (kSmiTag == 0));
+  STATIC_ASSERT((static_cast<unsigned>(kSmiShift) == kWRegSizeInBits) &&
+                (static_cast<unsigned>(kSmiValueSize) == kWRegSizeInBits) &&
+                (kSmiTag == 0));
   Push(src1.W(), wzr, src2.W(), wzr);
 }