OT: floats

[Daniel N]

On Saturday, 25 May 2024 at 07:47:13 UTC, Walter Bright wrote:
> On 5/24/2024 11:52 PM, Timon Gehr wrote:
>> It was avoidable, as even the x87 allows controlling the 
>> mantissa size (which is insufficient but "more" correct) or 
>> flushing floats and doubles to memory.
>
> Flushing it to memory was correct but was terribly slow.
>
>
>> D compilers are allowed by the spec e.g. to use 64-bit XMM 
>> registers to compute with 32-bit float intermediates, with 
>> incorrect rounding behavior.
>
> Nobody implemented that.

Just saw "Excess precision support" in the gcc changelog, which 
might interest you.
https://gcc.gnu.org/gcc-13/changes.html#cxx

"-std=gnu++20 it defaults to -fexcess-precision=fast"

I was aware of -ffast-math but not that the seemingly harmless 
enabling of gnu dialect extensions would change excess-precision!