To whom it may concern: As some of you may be aware, Paul Dennis (whirlicote on Github) and I (KloudKoder) are trying to enable floating-point (FP) instructions with explicit rounding modes (RMs) in WebAssembly. The motivation is to trivialize analog security via interval arithmetic (which provides guarantees about where a given real number resides). As part of our work with the WebAssembly Community Group, we were tasked with producing a prototype implementation in V8. The required changes are conceptually simple and at this point we're just looking for implementation guidance. For that matter, if you feel strongly one way or the other about this, then we invite your feedback.
Several months ago, Paul submitted a prototype design for their reference interpreter for some new FP instructions which include an explicit rounding mode. For example, instead of FP division, one could now have: divide_floor divide_ceil divide_chop divide_nearest_even (already existing as simply "divide") in the usual 32-bit and 64-bit widths. There are also new rounding instructions which convert between floats and ints, and promote or demote between precisions, all with an explicit RM. We've also added support for the extraction of arithmetic (trinary) or logical (binary) signs. For my part, I provided him with thousands of corner cases for testing against actual Intel FPU (IEEE754) hardware. There's full coverage of all unique instruction behavior, with some esoteric exceptions involving NaNs that are already the subject of relevant canonicalization efforts, absent any of this. While there are tens of new instructions, the implementation is actually quite repetitive, basically consisting of hardware RM switches before and after an FP operation. But if that's still too overwhelming, then we could start with sqrt_floor and/or divide. These are unary and binary instructions, respectively, the code for which would serve as templates for implementing the other FP instructions in the proposal. If you want to get into the weeds on all this, you can check out the relevant Github issue below: https://github.com/WebAssembly/rounding-mode-control/issues/2 We haven't signed the CLA yet but we're willing to do so if there's interest here. Ask us anything! Kloud Koder -- -- v8-dev mailing list v8-dev@googlegroups.com http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-dev+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-dev/CAB_Hu_YZ-B%3DQ7pP7B%3DP6Xf992jCZPQj%3DrCucggHEHo0GJTiP1w%40mail.gmail.com.
