Bug 1373290 - Move object/string pre-barrier null check to JIT code. r=nbp

js/src/jit/MacroAssembler.h

@@ -1037,6 +1037,8 @@ class MacroAssembler : public MacroAssemblerSpecific
     inline void branchPtr(Condition cond, const Address& lhs, ImmGCPtr rhs, Label* label) PER_SHARED_ARCH;
     inline void branchPtr(Condition cond, const Address& lhs, ImmWord rhs, Label* label) PER_SHARED_ARCH;
 
+    inline void branchPtr(Condition cond, const BaseIndex& lhs, ImmWord rhs, Label* label) PER_SHARED_ARCH;
+
     inline void branchPtr(Condition cond, const AbsoluteAddress& lhs, Register rhs, Label* label)
         DEFINED_ON(arm, arm64, mips_shared, x86, x64);
     inline void branchPtr(Condition cond, const AbsoluteAddress& lhs, ImmWord rhs, Label* label)
@@ -1654,6 +1656,8 @@ class MacroAssembler : public MacroAssemblerSpecific
 
         if (type == MIRType::Value)
             branchTestGCThing(Assembler::NotEqual, address, &done);
+        else if (type == MIRType::Object || type == MIRType::String)
+            branchPtr(Assembler::Equal, address, ImmWord(0), &done);
 
         Push(PreBarrierReg);
         computeEffectiveAddress(address, PreBarrierReg);

js/src/jit/VMFunctions.cpp

@@ -1433,15 +1433,15 @@ MarkValueFromIon(JSRuntime* rt, Value* vp)
 void
 MarkStringFromIon(JSRuntime* rt, JSString** stringp)
 {
-    if (*stringp)
-        TraceManuallyBarrieredEdge(&rt->gc.marker, stringp, "write barrier");
+    MOZ_ASSERT(*stringp);
+    TraceManuallyBarrieredEdge(&rt->gc.marker, stringp, "write barrier");
 }
 
 void
 MarkObjectFromIon(JSRuntime* rt, JSObject** objp)
 {
-    if (*objp)
-        TraceManuallyBarrieredEdge(&rt->gc.marker, objp, "write barrier");
+    MOZ_ASSERT(*objp);
+    TraceManuallyBarrieredEdge(&rt->gc.marker, objp, "write barrier");
 }
 
 void

js/src/jit/arm/MacroAssembler-arm-inl.h

@@ -1457,6 +1457,12 @@ MacroAssembler::branchPtr(Condition cond, wasm::SymbolicAddress lhs, Register rh
     branchPtr(cond, scratch2, rhs, label);
 }
 
+void
+MacroAssembler::branchPtr(Condition cond, const BaseIndex& lhs, ImmWord rhs, Label* label)
+{
+    branch32(cond, lhs, Imm32(rhs.value), label);
+}
+
 template <typename T>
 inline CodeOffsetJump
 MacroAssembler::branchPtrWithPatch(Condition cond, Register lhs, T rhs, RepatchLabel* label)

js/src/jit/arm64/MacroAssembler-arm64-inl.h

@@ -1032,6 +1032,17 @@ MacroAssembler::branchPtr(Condition cond, wasm::SymbolicAddress lhs, Register rh
     branchPtr(cond, scratch, rhs, label);
 }
 
+void
+MacroAssembler::branchPtr(Condition cond, const BaseIndex& lhs, ImmWord rhs, Label* label)
+{
+    vixl::UseScratchRegisterScope temps(this);
+    const Register scratch = temps.AcquireX().asUnsized();
+    MOZ_ASSERT(scratch != lhs.base);
+    MOZ_ASSERT(scratch != lhs.index);
+    loadPtr(lhs, scratch);
+    branchPtr(cond, scratch, rhs, label);
+}
+
 template <typename T>
 CodeOffsetJump
 MacroAssembler::branchPtrWithPatch(Condition cond, Register lhs, T rhs, RepatchLabel* label)

js/src/jit/mips-shared/MacroAssembler-mips-shared-inl.h

@@ -571,6 +571,13 @@ MacroAssembler::branchPtr(Condition cond, wasm::SymbolicAddress lhs, Register rh
     branchPtr(cond, SecondScratchReg, rhs, label);
 }
 
+void
+MacroAssembler::branchPtr(Condition cond, const BaseIndex& lhs, ImmWord rhs, Label* label)
+{
+    loadPtr(lhs, SecondScratchReg);
+    branchPtr(cond, SecondScratchReg, rhs, label);
+}
+
 template <typename T>
 CodeOffsetJump
 MacroAssembler::branchPtrWithPatch(Condition cond, Register lhs, T rhs, RepatchLabel* label)

js/src/jit/x64/Assembler-x64.h

@@ -871,6 +871,9 @@ class Assembler : public AssemblerX86Shared
           case Operand::MEM_REG_DISP:
             masm.cmpq_im(rhs.value, lhs.disp(), lhs.base());
             break;
+          case Operand::MEM_SCALE:
+            masm.cmpq_im(rhs.value, lhs.disp(), lhs.base(), lhs.index(), lhs.scale());
+            break;
           case Operand::MEM_ADDRESS32:
             masm.cmpq_im(rhs.value, lhs.address());
             break;

js/src/jit/x86-shared/MacroAssembler-x86-shared-inl.h

@@ -582,6 +582,12 @@ MacroAssembler::branchPtr(Condition cond, const Address& lhs, ImmWord rhs, Label
     branchPtrImpl(cond, lhs, rhs, label);
 }
 
+void
+MacroAssembler::branchPtr(Condition cond, const BaseIndex& lhs, ImmWord rhs, Label* label)
+{
+    branchPtrImpl(cond, lhs, rhs, label);
+}
+
 template <typename T, typename S, typename L>
 void
 MacroAssembler::branchPtrImpl(Condition cond, const T& lhs, const S& rhs, L label)