Original commit message:

    [turbofan] Fix -0 check for subnormals.

    Previously we'd check `x` for -0 by testing `(1.0 / x) == -Infinity`,
    but this will yield the wrong results when `x` is a subnormal, i.e.
    really close to 0.

    In CSA we already perform bit checks to test for -0, so teach TurboFan
    to do the same for comparisons to -0 (via `Object.is`). We introduce a
    new NumberIsMinusZero simplified operator to handle the case where
    SimplifiedLowering already knows that the input is a number.

    Bug: chromium:903043, v8:6882
    Change-Id: I0cb7c568029b461a92fc183104d5f359b4bfe7f4
    Reviewed-on: https://chromium-review.googlesource.com/c/1328802
    Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
    Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#57382}

Refs: v8/v8@56f6a76

Original commit message:

    [turbofan] Fix -0 check for subnormals.

    Previously we'd check `x` for -0 by testing `(1.0 / x) == -Infinity`,
    but this will yield the wrong results when `x` is a subnormal, i.e.
    really close to 0.

    In CSA we already perform bit checks to test for -0, so teach TurboFan
    to do the same for comparisons to -0 (via `Object.is`). We introduce a
    new NumberIsMinusZero simplified operator to handle the case where
    SimplifiedLowering already knows that the input is a number.

    Bug: chromium:903043, v8:6882
    Change-Id: I0cb7c568029b461a92fc183104d5f359b4bfe7f4
    Reviewed-on: https://chromium-review.googlesource.com/c/1328802
    Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
    Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#57382}

PR-URL: #25269
Refs: v8/v8@56f6a76
Fixes: #25268
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>