Matt Godbolt’s Compiler Explorer, developed in node.js, allows you to view assembly code as you type. Along with various versions of gcc, the tool also supports MSP430 gcc 4.5.3 and 5.3.0 versions.
Compiler Explorer is an interactive compiler. The left-hand pane shows editable C/C++/Rust/Go/D code. The right, the assembly output of having compiled the code with a given compiler and settings. Multiple compilers are supported, and the UI layout is configurable (the Golden Layout library is used for this).
The github link of the project is here with more detail on Matt’s blog.