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Re: underflow exceptions
On Fri, 25 May 2012, Marek Polacek wrote:
> I see one failure on x86_64:
> testing double (without inline functions)
> Failure: fma (-0x1.d2eaed6e8e9d3p-979, -0x1.4e066c62ac9ddp-63, -0x0.9245e6b003454p-1022) == -0x0.9245c09c5fb5dp-1022: Exception
> "Underflow" not set
This is probably an instance of the same issue as in bug 14152, but for
fma. I suggest updating the summary of that bug to reflect that the issue
applies to this fma test as well, and changing UNDERFLOW_EXCEPTION to
UNDERFLOW_EXCEPTION_OK in the test (with a comment above it referring to
bug 14152).
I generally do libm testing with --disable-multi-arch so that it's
predictable what version of a function is used and to be sure that the
generic versions are properly fixed. In this case, I suspect you had
multi-arch enabled, but a processor without FMA4 instructions, and this
combination meant your testing ended up using the dbl-64 version of
s_fma.c whereas mine used the ldbl-96 one (and this issue of missing
underflow exceptions may only arise when the operation is done in the same
internal precision as the final result).
--
Joseph S. Myers
joseph@codesourcery.com