[cfe-dev] [RFC] FP contract = on

[Renato Golin via cfe-dev]

Hey folks,

Some progress has been made since the first thread:

http://lists.llvm.org/pipermail/llvm-dev/2017-March/111129.html

And also I think the consensus is to enable "-ffp-contract=on" by
default (instead of "fast"), which seems to be working on some
preliminary tests I made.

I just ran the test-suite on x86_64 and AArch64. The former is ok, the
latter still has some failures:

MultiSource/Applications/oggenc/oggenc
MultiSource/Benchmarks/MiBench/telecomm-FFT/telecomm-fft
MultiSource/Benchmarks/VersaBench/beamformer/beamformer

SingleSource/Benchmarks/Linpack/linpack-pc
SingleSource/Benchmarks/Misc-C++/Large/sphereflake
SingleSource/Benchmarks/Polybench/datamining
SingleSource/Benchmarks/Polybench/linear-algebra
SingleSource/Benchmarks/Polybench/stencils

Sebastian, how's the progress to get those benchmarks contract-friendly?

We mainly need to make sure that the difference in precision is *just*
because the contraction, not something else, and hopefully reduce them
below e10-4 with some tricks, to avoid surprises.

cheers,
--renato