[cfe-dev] fixing overly-demanding-of-exact-equality FP tests: MultiSource/Benchmarks/MiBench/telecomm-FFT

[Abe Skolnik via cfe-dev]

Dear all,

As a result of my proposed patch at <https://reviews.llvm.org/D24481> being reverted b/c it 
breaks test-suite tests that either expect exact equality [as this one, i.e. "telecomm-FFT", 
currently does] or too-strict tolerance, I am investigating 20 tests and working on solutions. 
This is the first publicly-proposed solution, or at least the beginnings of one.

The first problem with "telecomm-FFT" is that the test is currently configured to capture the 
output [688111 bytes of floating-point text, including lots of spaces and just a few newlines], 
hash it, throw away the original text, then compare the hashes.  Unless somebody wants to 
rewrite this test in integer code [good luck ;-)], this obviously won`t "do".

Does anybody know of a way to have test-suite automatically uncompress a compressed reference 
file, run the test and compare [with "fpcmp" and a tolerance, in this case], then delete the 
temporarily-uncompressed reference file and compress the raw output [for post-run analysis]?  I 
don`t yet know enough about the inner workings of test-suite to write that by myself.

As for the tolerance, I experimentally derived the absolute tolerance 0.000002 using [after 
minimization] the following:

   > ../../../../tools/fpcmp -a 0.000001 new_reference_output 
/work/Abe/Sept._27_2016/LLVM_test-suite_build_004___AArch64___Clang_2016-09-07-20-03-19-b0768e8-master/MultiSource/Benchmarks/MiBench/telecomm-FFT/new_reference_output
   ../../../../tools/fpcmp: Compared: 3.610700e-02 and 3.610600e-02
   abs. diff = 1.000000e-06 rel.diff = 2.769623e-05
   Out of tolerance: rel/abs: 0.000000e+00/1.000000e-06

   > ../../../../tools/fpcmp -a 0.000002 new_reference_output 
/work/Abe/Sept._27_2016/LLVM_test-suite_build_004___AArch64___Clang_2016-09-07-20-03-19-b0768e8-master/MultiSource/Benchmarks/MiBench/telecomm-FFT/new_reference_output
   > echo $?
   0


... where the two runs were both on the same AArch64 device, once built with a compiler from 
this commit:

   commit b0768e805d1d33d730e5bd44ba578df043dfbc66
   Author: George Burgess IV <george.burgess.iv at gmail.com>
   Date:   Wed Sep 7 20:03:19 2016 +0000

... and the other with my fusion-enabling patch on top of that.

Regards,

Abe