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Partial WebAssembly backend

From: Pip Cet <pipcet at gmail dot com>

To: binutils at sourceware dot org

Date: Sat, 4 Mar 2017 16:30:02 +0000

Subject: Partial WebAssembly backend

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I'd like to announce a WebAssembly backend for the GNU toolchain (binutils, gcc, glibc) that I've been working on for a while. WebAssembly (https://www.w3.org/community/webassembly/) is an object file format for a virtual machine implementing conventional 32-bit integer/64-bit floating-point arithmetic. Version 1 has been released on February 28 (https://lists.w3.org/Archives/Public/public-webassembly/2017Feb/0002.html), and enabled in various browsers, including Mozilla. This binutils port produces and deals with ELF files containing WebAssembly code; WebAssembly modules (in the WebAssembly object file format) can be output using special linker scripts and -Obinary, but they cannot be used as input for any of the binutils programs at present. (While the gcc port, in particular, makes some decisions that negatively affect performance, the binutils port is quite general and should permit the assembly, linking, and manipulation of all WebAssembly code, provided it is still encapsulated in ELF files). The code is at https://github.com/pipcet/binutils-gdb, included from the larger project at https://github.com/pipcet/asmjs. Some documentation is available at https://github.com/pipcet/asmjs/blob/everything/wasm32.org (specific to the wasm32 target) and https://github.com/pipcet/asmjs/blob/everything/asmjs.org (for all three targets: asmjs, wasm32, and wasm64). The GitHub sources include support for using asm.js instead of wasm, and some rudimentary support for simulating a 64-bit machine using wasm. I'd appreciate any questions, comments or advice, and in particular I'd like to ask whether it is possible in theory to include this backend in the standard GNU binutils distribution; some work would be required on my end to do that, and I'm not sure it's worth the effort if there is no chance of inclusion at the end of the process. If anyone else has been or is planning to work on a WebAssembly backend, it would be great to hear from them, and maybe some of my code could be reused for that. Pip Cet