tree 230af0886cf3780bf5dadc2ce263efab28c6b586
parent b0ce9f0f4cff7df243b72e308ec863f012724475
author Thomas Lively <tlively@google.com> 1601623686 -0700
committer Thomas Lively <tlively@google.com> 1601623686 -0700

[WebAssembly] Emulate v128.const efficiently

v128.const was recently implemented in V8, but until it rolls into Chrome
stable, we can't enable it in the WebAssembly backend without breaking origin
trial users. So far we have been lowering build_vectors that would otherwise
have been lowered to v128.const to splats followed by sequences of replace_lane
instructions to initialize each lane individually. That produces large and
inefficient code, so this patch introduces new logic to lower integer vector
constants to a single i64x2.splat where possible, with at most a single
i64x2.replace_lane following it if necessary.

Adapted from a patch authored by @omnisip.

Differential Revision: https://reviews.llvm.org/D88591