[PATCH 3/4] math: signal underflow for fmaf results that are tiny before rounding

[Matt Turner]

On Tue, 4 Aug 2026, Joseph Myers wrote:

> As with the previous patch, is this general for after-rounding
> architectures, or specific to an Alpha hardware bug?

Specific to Alpha.  On x86_64 without this patch

  fmaf (-0x8p-152, 0x8.8p-4, -0x3.fffff8p-128) -> -0x1p-126

raises underflow already.  I answered this at more length on 2/4, which
has the worked example.

Please drop this one too.  It will come back conditional, along with 2/4.

Matt