We should disable this on Aurora and probably Nightly as well. Until bug 913282 is fixed, float32 can regress performance for things like Math.abs(float32array[x]), because the abs call is no longer inlined. See the following benchmarks (from bug 924856) for instance: http://opera-mage.github.io/webarraymath/benchmark/

I will do a Try push before landing this.

Comment on attachment 821831 [details] [diff] [review] Patch for Aurora Review of attachment 821831 [details] [diff] [review]: ----------------------------------------------------------------- Sooo, I lost my bugzilla rights when changing email address and I can't even r+ this patch, so this message can be considered as a voucher for a r+. ::: js/src/jit/x86/CodeGenerator-x86.cpp @@ +594,5 @@ > > Address dstAddr(ptr, (int32_t) mir->base()); > if (vt == ArrayBufferView::TYPE_FLOAT32) { > + JS_ASSERT(mir->value()->type() == MIRType_Double); > + masm.cvtsd2ss(ToFloatRegister(value), ScratchFloatReg); Could you add a reference to this bug here too, please?

You have your bits back now. (And, uh, really, the de-MoCo-ification bit strips those? That's kind of really surprising.)

Comment on attachment 821831 [details] [diff] [review] Patch for Aurora Review of attachment 821831 [details] [diff] [review]: ----------------------------------------------------------------- Sooo, I lost my bugzilla rights when changing email address and I can't even r+ this patch, so this message can be considered as a voucher for a r+.

AFAIK, the intention was to have float32 enabled on Nightly, but disabled for Beta through Release. Turning float32 off entirely will hurt, since fuzzers will no longer exercise any of the float32-related code. Could we instead hide float32 support behind one of those preferences that automatically switch to false for Beta/Release builds?

(In reply to Sean Stangl [:sstangl] from comment #6) > AFAIK, the intention was to have float32 enabled on Nightly, but disabled > for Beta through Release. Turning float32 off entirely will hurt, since > fuzzers will no longer exercise any of the float32-related code. This patch will only disable it for Aurora (26). I think with bug 913282 and bug 930477 we can leave it turned on for 27.

Comment on attachment 821831 [details] [diff] [review] Patch for Aurora [Approval Request Comment] Bug caused by (feature/regressing bug #): Bug 888109 User impact if declined: Performance regressions Testing completed (on m-c, etc.): Green on Try [0] Risk to taking this patch (and alternatives if risky): Low, disables a new optimization. String or IDL/UUID changes made by this patch: None. [0] https://tbpl.mozilla.org/?tree=Try&rev=b2d64fa5d225

I assume this bug can be resolved fixed because the patch landed on Aurora (26) and bug 913282 was fixed in Nightly 27.