[Bug rtl-optimization/61494] -fsignaling-nans not taken into account for x - 0.0

[pangbw at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61494

baoshan <pangbw at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |pangbw at gmail dot com

--- Comment #2 from baoshan <pangbw at gmail dot com> ---
Looking at the function simplify_binary_operation_1, I can see "!HONOR_SNANS
(mode)" has been added in a few places to prevent the incorrect transformation,
I believe to fix the issue we just add it to other places it should be there.

But the question is which place should we add this predication?
For case 1: "X - 0" to "X" we may say it is needed, but what about case 2:
"(X&C1)|C2" to "X|C2"? The quiet NaN would be generated but not in the original
location; if we think it is not needed I will think for the case 1 it is also
not needed because I believe the signaling 'X' would be used later and the
quite NaN would be generated eventually.
If we think for both of cases the predication is necessary, I would
think(suggest) every transformation in this function should be prohibited if
HONOR_SNANS (mode) is true.