[LLVMdev] Error running spec benchmark with FMA4 on X86

[Anitha Boyapati]

Hi All,

I am facing miscompare error when running povray (and few other C/C++
benchmarks) from spec cpu2006 suite enabling FMA4 (and disabling FMA3). I
have used -ffp-contract=fast to turn on this option. (Compilation options
and targets pasted below).

>>>>>>>>
clang version 3.2 (trunk 163295:163308) (llvm/trunk 163295)
Target: x86_64-unknown-linux-gnu
Thread model: posix


(Options to clang)

 -O3 -march=bdver2 -mavx -mno-fma -mfma4 -ffp-contract=fast -save-temps

<<<<<<<

Note that BDVER2 supports both FMA3 and FMA4. Also the benchmark was
run *successfully* when FMA3 was enabled. Reducing the testcase might take
more time but has anyone noticed this issue?

For those interested, miscompare message is as below

*** Miscompare of SPEC-benchmark.log; for details see
    CPU2006/peak_ref_llvm.0037/SPEC-benchmark.log.mis

0050:  Pixels:             1280   Samples:            8960
           Pixels:             1280   Samples:           47360

 ^
0051:  Rays:               8960   Saved:                 0   Max Level: 1/5
           Rays:              47360   Saved:                 0   Max Level:
1/5
                                          ^
0055:  CSG Intersection                232960               0
           Box                              47360               0
           ^
0056:  Plane                           537600          510304
          Cone/Cylinder                  1515520               0
           ^
...







-- 
* Anitha*
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