Allow GPU variables to influence control flow in JS API (if statements, for loops)

[PWhiddy]

[PWhiddy]

This means support for branching (if/else) statements whose conditions depend on variables defined in terms of time/x/y/z/p

[PWhiddy]

Example code tree to study:

// Life, Universe, and Everything
var answer = 6 * 7;

let x = 0.4;

for (let i=0; i<7; i++) {

   if (x-i<4){
      x += 0.1;
   } else if (3<5) {
      x = 0.3;
   } else {
      x = 3;
   
   }

}

produces:

{
    "type": "Program",
    "body": [
        {
            "type": "VariableDeclaration",
            "declarations": [
                {
                    "type": "VariableDeclarator",
                    "id": {
                        "type": "Identifier",
                        "name": "answer"
                    },
                    "init": {
                        "type": "BinaryExpression",
                        "operator": "*",
                        "left": {
                            "type": "Literal",
                            "value": 6,
                            "raw": "6"
                        },
                        "right": {
                            "type": "Literal",
                            "value": 7,
                            "raw": "7"
                        }
                    }
                }
            ],
            "kind": "var"
        },
        {
            "type": "VariableDeclaration",
            "declarations": [
                {
                    "type": "VariableDeclarator",
                    "id": {
                        "type": "Identifier",
                        "name": "x"
                    },
                    "init": {
                        "type": "Literal",
                        "value": 0.4,
                        "raw": "0.4"
                    }
                }
            ],
            "kind": "let"
        },
        {
            "type": "ForStatement",
            "init": {
                "type": "VariableDeclaration",
                "declarations": [
                    {
                        "type": "VariableDeclarator",
                        "id": {
                            "type": "Identifier",
                            "name": "i"
                        },
                        "init": {
                            "type": "Literal",
                            "value": 0,
                            "raw": "0"
                        }
                    }
                ],
                "kind": "let"
            },
            "test": {
                "type": "BinaryExpression",
                "operator": "<",
                "left": {
                    "type": "Identifier",
                    "name": "i"
                },
                "right": {
                    "type": "Literal",
                    "value": 7,
                    "raw": "7"
                }
            },
            "update": {
                "type": "UpdateExpression",
                "operator": "++",
                "argument": {
                    "type": "Identifier",
                    "name": "i"
                },
                "prefix": false
            },
            "body": {
                "type": "BlockStatement",
                "body": [
                    {
                        "type": "IfStatement",
                        "test": {
                            "type": "BinaryExpression",
                            "operator": "<",
                            "left": {
                                "type": "BinaryExpression",
                                "operator": "-",
                                "left": {
                                    "type": "Identifier",
                                    "name": "x"
                                },
                                "right": {
                                    "type": "Identifier",
                                    "name": "i"
                                }
                            },
                            "right": {
                                "type": "Literal",
                                "value": 4,
                                "raw": "4"
                            }
                        },
                        "consequent": {
                            "type": "BlockStatement",
                            "body": [
                                {
                                    "type": "ExpressionStatement",
                                    "expression": {
                                        "type": "AssignmentExpression",
                                        "operator": "+=",
                                        "left": {
                                            "type": "Identifier",
                                            "name": "x"
                                        },
                                        "right": {
                                            "type": "Literal",
                                            "value": 0.1,
                                            "raw": "0.1"
                                        }
                                    }
                                }
                            ]
                        },
                        "alternate": {
                            "type": "IfStatement",
                            "test": {
                                "type": "BinaryExpression",
                                "operator": "<",
                                "left": {
                                    "type": "Literal",
                                    "value": 3,
                                    "raw": "3"
                                },
                                "right": {
                                    "type": "Literal",
                                    "value": 5,
                                    "raw": "5"
                                }
                            },
                            "consequent": {
                                "type": "BlockStatement",
                                "body": [
                                    {
                                        "type": "ExpressionStatement",
                                        "expression": {
                                            "type": "AssignmentExpression",
                                            "operator": "=",
                                            "left": {
                                                "type": "Identifier",
                                                "name": "x"
                                            },
                                            "right": {
                                                "type": "Literal",
                                                "value": 0.3,
                                                "raw": "0.3"
                                            }
                                        }
                                    }
                                ]
                            },
                            "alternate": {
                                "type": "BlockStatement",
                                "body": [
                                    {
                                        "type": "ExpressionStatement",
                                        "expression": {
                                            "type": "AssignmentExpression",
                                            "operator": "=",
                                            "left": {
                                                "type": "Identifier",
                                                "name": "x"
                                            },
                                            "right": {
                                                "type": "Literal",
                                                "value": 3,
                                                "raw": "3"
                                            }
                                        }
                                    }
                                ]
                            }
                        }
                    }
                ]
            }
        }
    ],
    "sourceType": "script"
}

[PWhiddy]

first need to convert comparison ops to function calls (>, <, ==)