[all-commits] [llvm/llvm-project] 6c9c69: [flang] Retain the sign of the argument for the re...

[vdonaldson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6c9c69bd761653372999c09c7862290f8793068a
      https://github.com/llvm/llvm-project/commit/6c9c69bd761653372999c09c7862290f8793068a
  Author: V Donaldson <vdonaldson at nvidia.com>
  Date:   2023-05-26 (Fri, 26 May 2023)

  Changed paths:
    M flang/runtime/numeric.cpp

  Log Message:
  -----------
  [flang] Retain the sign of the argument for the result of fraction(0)

The f18 clause 16.9.80 description of the FRACTION(X) intrinsic states:

    Result Value. The result has the value ....
    If X has the value zero, the result is zero.
    If X is an IEEE NaN, the result is that NaN.
    If X is an IEEE infinity, the result is an IEEE NaN.

This clause does not specify whether fraction(-0.0) should be -0.0 or +0.0.
However, a folded result and a runtime result should be consistent, and
returning -0.0 is more in line with the result for fraction(NaN).

For this test:

  print '(2f6.1)', 0.0, fraction(0.0)
  call f(0.0)
  print '(2f6.1)', -0.0, fraction(-0.0)
  call f(-0.0)
  end

  subroutine f(x)
    print '(2f6.1)', x, fraction(x)
  end

Current output is:

   0.0   0.0
   0.0   0.0
  -0.0  -0.0
  -0.0   0.0

Change that to:

   0.0   0.0
   0.0   0.0
  -0.0  -0.0
  -0.0  -0.0