Bug 1636916 part 1 - Rename unboxGCThingForPreBarrierTrampoline to unboxGCThingForGCBarrier. r=jonco

Also add ValueOperand overloads on 64-bit platforms.

A later patch will also call this for the post barrier.

Differential Revision: https://phabricator.services.mozilla.com/D74647

js/src/jit/MacroAssembler.cpp

@@ -3353,7 +3353,7 @@ void MacroAssembler::emitPreBarrierFastPath(JSRuntime* rt, MIRType type,
 
   // Load the GC thing in temp1.
   if (type == MIRType::Value) {
-    unboxGCThingForPreBarrierTrampoline(Address(PreBarrierReg, 0), temp1);
+    unboxGCThingForGCBarrier(Address(PreBarrierReg, 0), temp1);
   } else {
     MOZ_ASSERT(type == MIRType::Object || type == MIRType::String ||
                type == MIRType::Shape || type == MIRType::ObjectGroup);

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

@@ -876,7 +876,7 @@ class MacroAssemblerARMCompat : public MacroAssemblerARM {
   void unboxValue(const ValueOperand& src, AnyRegister dest, JSValueType type);
 
   // See comment in MacroAssembler-x64.h.
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     load32(ToPayload(src), dest);
   }
 

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

@@ -1392,11 +1392,15 @@ class MacroAssemblerCompat : public vixl::MacroAssembler {
   }
 
   // See comment in MacroAssembler-x64.h.
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     loadPtr(src, dest);
     And(ARMRegister(dest, 64), ARMRegister(dest, 64),
         Operand(JS::detail::ValueGCThingPayloadMask));
   }
+  void unboxGCThingForGCBarrier(const ValueOperand& src, Register dest) {
+    And(ARMRegister(dest, 64), ARMRegister(src.valueReg(), 64),
+        Operand(JS::detail::ValueGCThingPayloadMask));
+  }
 
   inline void unboxValue(const ValueOperand& src, AnyRegister dest,
                          JSValueType type);

js/src/jit/mips32/MacroAssembler-mips32.h

@@ -352,7 +352,7 @@ class MacroAssemblerMIPSCompat : public MacroAssemblerMIPS {
   void unboxObjectOrNull(const Address& src, Register dest);
   void unboxValue(const ValueOperand& src, AnyRegister dest, JSValueType);
 
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     unboxObject(src, dest);
   }
 

js/src/jit/mips64/MacroAssembler-mips64.h

@@ -379,7 +379,7 @@ class MacroAssemblerMIPS64Compat : public MacroAssemblerMIPS64 {
     ma_dins(dest, zero, Imm32(JSVAL_TAG_SHIFT + 3), Imm32(1));
   }
 
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     loadPtr(src, dest);
     ma_dext(dest, dest, Imm32(0), Imm32(JSVAL_TAG_SHIFT));
   }

js/src/jit/none/MacroAssembler-none.h

@@ -495,7 +495,8 @@ class MacroAssemblerNone : public Assembler {
     MOZ_CRASH();
   }
   void unboxNonDouble(const Address&, Register, JSValueType) { MOZ_CRASH(); }
-  void unboxGCThingForPreBarrierTrampoline(const Address&, Register) {
+  template <typename T>
+  void unboxGCThingForGCBarrier(const T&, Register) {
     MOZ_CRASH();
   }
   template <typename T>

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

@@ -843,14 +843,19 @@ class MacroAssemblerX64 : public MacroAssemblerX86Shared {
     andq(scratch, dest);
   }
 
-  // This should only be used for the pre-barrier trampoline, to unbox a
-  // string/symbol/object Value. It's fine there because we don't depend on
-  // the actual Value type. In almost all other cases, this would be
+  // This should only be used for GC barrier code, to unbox a GC thing Value.
+  // It's fine there because we don't depend on the actual Value type (all Cells
+  // are treated the same way). In almost all other cases this would be
   // Spectre-unsafe - use unboxNonDouble and friends instead.
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     movq(ImmWord(JS::detail::ValueGCThingPayloadMask), dest);
     andq(Operand(src), dest);
   }
+  void unboxGCThingForGCBarrier(const ValueOperand& src, Register dest) {
+    MOZ_ASSERT(src.valueReg() != dest);
+    movq(ImmWord(JS::detail::ValueGCThingPayloadMask), dest);
+    andq(src.valueReg(), dest);
+  }
 
   // Extended unboxing API. If the payload is already in a register, returns
   // that register. Otherwise, provides a move to the given scratch register,

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

@@ -808,7 +808,7 @@ class MacroAssemblerX86 : public MacroAssemblerX86Shared {
                          JSValueType type);
 
   // See comment in MacroAssembler-x64.h.
-  void unboxGCThingForPreBarrierTrampoline(const Address& src, Register dest) {
+  void unboxGCThingForGCBarrier(const Address& src, Register dest) {
     movl(payloadOf(src), dest);
   }