On Thu, May 19, 2016 at 2:59 AM, Emanuel Hoogeveen
<emanuel.hoogev...@gmail.com> wrote:
>
> They do get the baseline compiler, which can still be significantly faster 
> than the interpreter, but Ion requires SSE2. Since the runtime detection does 
> just turn Ion off altogether, I don't know if we would gain much by removing 
> it (the ability to disable Ion isn't going away).
>

We will have to make a similar decision for WebAssembly. Odin (our
Ion-based asm.js compiler) requires SSE2, but there we can at least
use the much slower 'normal JS' path. For WebAssembly, we have the
following options IIUC:

(1) Don't support wasm on those ancient CPUs. This may work for a
while, but at some point we may include wasm modules in Firefox and
add-ons, normal websites will start to use it, etc.
(2) Add x87 floating-point support to the wasm baseline JIT - very
complicated and likely not worth it.
(3) Call into C++ for all floating point and SIMD operations. This
will be horribly slow.
(4) Add a wasm interpreter. Again, likely not worth the effort if it's
just for this.

Jan
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