Performance problem when using WebGL2

[genosage]

I noticed that the modernizeShader function can port shaders to GLSL 3.0. It did this by using replaceInSourceString and replaceInSourceRegex to replace strings which is String.prototype.replace() in deed.

This will cause severe performance problem when there are many draw calls. The shader cache can not handle this kind of situation because it can only get the keyword after combining shaders.

(A better way may be assigning an identifier and use it as the keyword to avoid calling replace functions each draw call.)

// ShaderCache.js
  var vertexShaderText = vertexShaderSource.createCombinedVertexShader(
    this._context
  );
  var fragmentShaderText = fragmentShaderSource.createCombinedFragmentShader(
    this._context
  );

  var keyword =
    vertexShaderText + fragmentShaderText + JSON.stringify(attributeLocations);

[ebogo1]

Thanks @genosage - we're aware that modernizeShader needs to be reworked and it's part of our WebGL 2 roadmap: #797

I've added a comment there with your suggestion for future reference but I'll close this issue to avoid duplicates.