[turbofan] Add backend support for float32.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index 82b4500d5f0a4a2b983ea3ab423ded6e8831acd9..9b1c5e6746df488b42e11d96febf63d772202a89 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -276,6 +276,11 @@ struct FPRegister : public CPURegister {
       (kAllocatableHighRangeEnd - kAllocatableHighRangeBegin + 1);
   static int NumAllocatableRegisters() { return kMaxNumAllocatableRegisters; }
 
+  // TODO(turbofan): Proper float32 support.
+  static int NumAllocatableAliasedRegisters() {
+    return NumAllocatableRegisters();
+  }
+
   // Return true if the register is one that crankshaft can allocate.
   bool IsAllocatable() const {
     return (Bit() & kAllocatableFPRegisters) != 0;