Bug 1820855 - [hazards] Extract out a function matcher r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D171896

js/src/devtools/rootAnalysis/CFG.js

@@ -699,6 +699,45 @@ function edgeStartsValueLiveRange(edge, variable)
     return false;
 }
 
+// Return the result of a `matcher` callback on the call found in the given
+// `edge`, if the edge is a direct call to a named function (if not, return false).
+// `matcher` is given the name of the callee (actually, a tuple
+// [fully qualified name, base name]), an array of expressions containing the
+// arguments, and if the result of the call is assigned to a variable,
+// the expression representing that variable(the lhs).
+//
+// https://firefox-source-docs.mozilla.org/js/HazardAnalysis/CFG.html for
+// documentation of the data structure used here.
+function matchEdgeCall(edge, matcher) {
+    if (edge.Kind != "Call") {
+        return false;
+    }
+
+    const callee = edge.Exp[0];
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Exp[0].Kind == 'Var' &&
+        edge.Exp[0].Variable.Kind == 'Func') {
+        const calleeName = edge.Exp[0].Variable.Name;
+        const args = edge.PEdgeCallArguments;
+        const argExprs = args ? args.Exp : [];
+        const lhs = edge.Exp[1]; // May be undefined
+        return matcher(calleeName, argExprs, lhs);
+    }
+
+    return false;
+}
+
+function edgeMarksVariableGCSafe(edge, variable) {
+    return matchEdgeCall(edge, (calleeName, argExprs, _lhs) => {
+        // explicit JS_HAZ_VARIABLE_IS_GC_SAFE annotation
+        return (calleeName[1] == 'MarkVariableAsGCSafe' &&
+            calleeName[0].includes("JS::detail::MarkVariableAsGCSafe") &&
+            argExprs.length == 1 &&
+            expressionIsVariable(argExprs[0], variable));
+    });
+}
+
 // Match an optional <namespace>:: followed by the class name,
 // and then an optional template parameter marker.
 //
@@ -748,30 +787,20 @@ function edgeEndsValueLiveRange(edge, variable, body)
     if (edge.Kind != "Call")
         return false;
 
-    var callee = edge.Exp[0];
-
-    if (edge.Type.Kind == 'Function' &&
-        edge.Exp[0].Kind == 'Var' &&
-        edge.Exp[0].Variable.Kind == 'Func' &&
-        edge.Exp[0].Variable.Name[1] == 'MarkVariableAsGCSafe' &&
-        edge.Exp[0].Variable.Name[0].includes("JS::detail::MarkVariableAsGCSafe") &&
-        expressionIsVariable(edge.PEdgeCallArguments.Exp[0], variable))
-    {
+    if (edgeMarksVariableGCSafe(edge, variable)) {
         // explicit JS_HAZ_VARIABLE_IS_GC_SAFE annotation
         return true;
     }
 
     const decl = lookupVariable(body, variable);
 
-    if (edge.Type.Kind == 'Function' &&
-        edge.Exp[0].Kind == 'Var' &&
-        edge.Exp[0].Variable.Kind == 'Func' &&
-        edge.Exp[0].Variable.Name[1] == 'move' &&
-        edge.Exp[0].Variable.Name[0].includes('std::move(') &&
-        expressionIsDeclaredVariable(edge.PEdgeCallArguments.Exp[0], decl) &&
-        edge.Exp[1].Kind == 'Var' &&
-        edge.Exp[1].Variable.Kind == 'Temp')
-    {
+    if (matchEdgeCall(edge, (calleeName, argExprs, lhs) => {
+        return calleeName[1] == 'move' && calleeName[0].includes('std::move(') &&
+            expressionIsDeclaredVariable(argExprs[0], decl) &&
+            lhs &&
+            lhs.Kind == 'Var' &&
+            lhs.Variable.Kind == 'Temp';
+    })) {
         // temp = std::move(var)
         //
         // If var is a UniquePtr, and we pass it into something that takes
@@ -808,6 +837,8 @@ function edgeEndsValueLiveRange(edge, variable, body)
           return true;
     }
 
+    const callee = edge.Exp[0];
+
     if (edge.Type.Kind == 'Function' &&
         edge.Type.TypeFunctionCSU &&
         edge.PEdgeCallInstance &&