Bug 1720032 - Part 1: Mark Check{Return,This,ThisReinit} as throwing instructions. r=jandem

Check{Return,This} can throw an exception and therefore must record this in
their alias set.

CheckThisReinit doesn't strictly require this change, because this instruction
is currently only used in situations where a resume point is constructed anway,
but it seemed more consistent to handle it the same way as Check{Return,This}.

Differential Revision: https://phabricator.services.mozilla.com/D119630

js/src/jit-test/tests/class/bug1720032-1.js

@@ -0,0 +1,27 @@
+function main() {
+  class Base {}
+
+  class Derived extends Base {
+    constructor() {
+      super();
+
+      let v = 0xffff;
+
+      try {
+        // Ensure this statement doesn't get DCE'ed.
+        v &= 0xff;
+
+        // Returning a primitive value throws.
+        return 0;
+      } catch {}
+
+      assertEq(v, 255);
+    }
+  }
+
+  for (let i = 0; i < 15; i++) {
+    new Derived();
+  }
+}
+main();
+main();

js/src/jit-test/tests/class/bug1720032-2.js

@@ -0,0 +1,27 @@
+function main() {
+  class Base {}
+
+  class Derived extends Base {
+    constructor() {
+      let v = 0xffff;
+
+      try {
+        // Ensure this statement doesn't get DCE'ed.
+        v &= 0xff;
+
+        // Accessing |this| throws when |super()| wasn't yet called.
+        this;
+      } catch {}
+
+      assertEq(v, 255);
+
+      super();
+    }
+  }
+
+  for (let i = 0; i < 15; i++) {
+    new Derived();
+  }
+}
+main();
+main();

js/src/jit-test/tests/class/bug1720032-3.js

@@ -0,0 +1,27 @@
+function main() {
+  class Base {}
+
+  class Derived extends Base {
+    constructor() {
+      super();
+
+      let v = 0xffff;
+
+      try {
+        // Ensure this statement doesn't get DCE'ed.
+        v &= 0xff;
+
+        // Calling |super()| twice throws an error.
+        super();
+      } catch {}
+
+      assertEq(v, 255);
+    }
+  }
+
+  for (let i = 0; i < 15; i++) {
+    new Derived();
+  }
+}
+main();
+main();

js/src/jit/MIR.cpp

@@ -5826,6 +5826,18 @@ AliasSet MCheckObjCoercible::getAliasSet() const {
   return AliasSet::Store(AliasSet::ExceptionState);
 }
 
+AliasSet MCheckReturn::getAliasSet() const {
+  return AliasSet::Store(AliasSet::ExceptionState);
+}
+
+AliasSet MCheckThis::getAliasSet() const {
+  return AliasSet::Store(AliasSet::ExceptionState);
+}
+
+AliasSet MCheckThisReinit::getAliasSet() const {
+  return AliasSet::Store(AliasSet::ExceptionState);
+}
+
 AliasSet MIsPackedArray::getAliasSet() const {
   return AliasSet::Load(AliasSet::ObjectFields);
 }

js/src/jit/MIROps.yaml

@@ -1913,7 +1913,7 @@
     thisValue: Value
   result_type: Value
   guard: true
-  alias_set: none
+  alias_set: custom
 
 - name: CheckThis
   operands: 
@@ -1921,7 +1921,7 @@
   result_type: Value
   guard: true
   folds_to: custom
-  alias_set: none
+  alias_set: custom
 
 - name: AsyncResolve
   operands:
@@ -1953,7 +1953,7 @@
   result_type: Value
   guard: true
   folds_to: custom
-  alias_set: none
+  alias_set: custom
 
 - name: Generator
   gen_boilerplate: false

js/src/jit/WarpBuilder.cpp

@@ -2139,20 +2139,20 @@ bool WarpBuilder::build_CheckClassHeritage(BytecodeLocation loc) {
   return resumeAfter(ins, loc);
 }
 
-bool WarpBuilder::build_CheckThis(BytecodeLocation) {
+bool WarpBuilder::build_CheckThis(BytecodeLocation loc) {
   MDefinition* def = current->pop();
   auto* ins = MCheckThis::New(alloc(), def);
   current->add(ins);
   current->push(ins);
-  return true;
+  return resumeAfter(ins, loc);
 }
 
-bool WarpBuilder::build_CheckThisReinit(BytecodeLocation) {
+bool WarpBuilder::build_CheckThisReinit(BytecodeLocation loc) {
   MDefinition* def = current->pop();
   auto* ins = MCheckThisReinit::New(alloc(), def);
   current->add(ins);
   current->push(ins);
-  return true;
+  return resumeAfter(ins, loc);
 }
 
 bool WarpBuilder::build_Generator(BytecodeLocation loc) {
@@ -2401,7 +2401,7 @@ bool WarpBuilder::build_AsyncAwait(BytecodeLocation loc) {
   return resumeAfter(asyncAwait, loc);
 }
 
-bool WarpBuilder::build_CheckReturn(BytecodeLocation) {
+bool WarpBuilder::build_CheckReturn(BytecodeLocation loc) {
   MOZ_ASSERT(!script_->noScriptRval());
 
   MDefinition* returnValue = current->getSlot(info().returnValueSlot());
@@ -2410,7 +2410,7 @@ bool WarpBuilder::build_CheckReturn(BytecodeLocation) {
   auto* ins = MCheckReturn::New(alloc(), returnValue, thisValue);
   current->add(ins);
   current->setSlot(info().returnValueSlot(), ins);
-  return true;
+  return resumeAfter(ins, loc);
 }
 
 void WarpBuilder::buildCheckLexicalOp(BytecodeLocation loc) {