This got fixed by this change:
    https://crrev.com/32a2ab0c724673961aa145ab63c79a29e6d28fa8

Adding a smaller mjsunit test capturing the issue (was with idiv register allocation).

BUG= https://bugs.chromium.org/p/chromium/issues/detail?id=593283
R=aseemgarg@chromium.org,titzer@chromium.org
LOG=N
TEST=asm-wasm-copy

Review URL: https://codereview.chromium.org/1820163002

Cr-Commit-Position: refs/heads/master@{#35041}