[all-commits] [llvm/llvm-project] 60a252: [APFloat] prevent NaN morphing into Inf on convers...

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  Branch: refs/heads/release/11.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 60a25202a7dd1e00067fcfce512086ebf3788537
      https://github.com/llvm/llvm-project/commit/60a25202a7dd1e00067fcfce512086ebf3788537
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-09-30 (Wed, 30 Sep 2020)

  Changed paths:
    M llvm/lib/Support/APFloat.cpp
    M llvm/test/Transforms/ConstProp/cast.ll
    M llvm/unittests/ADT/APFloatTest.cpp

  Log Message:
  -----------
  [APFloat] prevent NaN morphing into Inf on conversion (PR43907)

We shift the significand right on a truncation, but that needs to be made NaN-safe:
always set at least 1 bit in the significand.
https://llvm.org/PR43907

See D88238 for the likely follow-up (but needs some plumbing fixes before it can proceed).

Differential Revision: https://reviews.llvm.org/D87835

(cherry picked from commit e34bd1e0b03d20a506ada156d87e1b3a96d82fa2)