diff --git a/js/src/ion/arm/MacroAssembler-arm.cpp b/js/src/ion/arm/MacroAssembler-arm.cpp
index 938ec450ceb..f1634ad2bb8 100644
--- a/js/src/ion/arm/MacroAssembler-arm.cpp
+++ b/js/src/ion/arm/MacroAssembler-arm.cpp
@@ -2001,6 +2001,12 @@ MacroAssemblerARMCompat::subPtr(const Address &addr, const Register dest)
     ma_sub(ScratchRegister, dest);
 }
 
+void
+MacroAssemblerARMCompat::subPtr(const Register &src, const Register &dest)
+{
+    ma_sub(src, dest);
+}
+
 void
 MacroAssemblerARMCompat::addPtr(Imm32 imm, const Register dest)
 {
diff --git a/js/src/ion/arm/MacroAssembler-arm.h b/js/src/ion/arm/MacroAssembler-arm.h
index 9d168bd14de..d961c1b3ac1 100644
--- a/js/src/ion/arm/MacroAssembler-arm.h
+++ b/js/src/ion/arm/MacroAssembler-arm.h
@@ -1042,6 +1042,7 @@ class MacroAssemblerARMCompat : public MacroAssemblerARM
 
     void subPtr(Imm32 imm, const Register dest);
     void subPtr(const Address &addr, const Register dest);
+    void subPtr(const Register &src, const Register &dest);
     void addPtr(Imm32 imm, const Register dest);
     void addPtr(Imm32 imm, const Address &dest);
     void addPtr(ImmWord imm, const Register dest) {