What is the problem with the vfmadd231ps instruction which throws a floating point Exception?
00007ff9`88f05108 62b26558b81482 vfmadd231ps zmm2,zmm3,dword bcst [rdx+r8*4] ds:00000220`7de9dc00=00000000
0:112> .exr -1
ExceptionAddress: 00007ff988f05108
ExceptionCode: c0000090
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 0000000000000000
Parameter[1]: 0000000000001923
0:112> rZ
zmm0=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
zmm1=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
zmm2=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
zmm3=0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0:112> r zmm2:f
zmm2= 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0:112> r zmm3:f
zmm3= 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0:112> r zmm3:ub
zmm3= 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0:112> r zmm2:ub
zmm2= 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0:112> db 0220`7de9dc00 L0x40
00000220`7de9dc00 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
00000220`7de9dc10 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
00000220`7de9dc20 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
00000220`7de9dc30 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
mxcsr=1923
According to https://help.totalview.io/previous_releases/2019/html/index.html#page/Reference_Guide/Intelx86MXSCRRegister.html
the flag 0x1923 indicates
- 0x1 Invalid Operation Flag
- 0x2 Denormal Flag
- 0x20 Precision Flag
- 0x1000 Precision Mask
- 0x100 Denormal Mask
- 0x800 Underflow Mask
Which value of the register is responsible for throwing an exception and what is wrong with the inputs? I am no AVX expert. To me Fused Multiply Add with all zeros looks ok to me.