instruction: 0.753
syscall: 0.136
runtime: 0.111



instruction 'denbcdq' misbehaving

Instruction 'denbcdq' appears to have no effect.  Test case attached.

On ppc64le native:
--
gcc -g -O -mcpu=power9 bcdcfsq.c test-denbcdq.c -o test-denbcdq
$ ./test-denbcdq
0x00000000000000000000000000000000
0x0000000000000000000000000000000c
0x22080000000000000000000000000000
$ ./test-denbcdq 1
0x00000000000000000000000000000001
0x0000000000000000000000000000001c
0x22080000000000000000000000000001
$ ./test-denbcdq $(seq 0 99)
0x00000000000000000000000000000064
0x0000000000000000000000000000100c
0x22080000000000000000000000000080
--

With "qemu-ppc64le -cpu power9"
--
$ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq
0x00000000000000000000000000000000
0x0000000000000000000000000000000c
0x0000000000000000000000000000000c
$ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq 1
0x00000000000000000000000000000001
0x0000000000000000000000000000001c
0x0000000000000000000000000000001c
$ qemu-ppc64le -cpu power9 -L [...] ./test-denbcdq $(seq 100)
0x00000000000000000000000000000064
0x0000000000000000000000000000100c
0x0000000000000000000000000000100c
--

I started looking at the code, but I got confused rather quickly.  Could be related to endianness? I think denbcdq arrived on the scene before little-endian was a big deal.  Maybe something to do with utilizing implicit floating-point register pairs...  I don't think the right data is getting to helper_denbcdq, which would point back to the gen_fprp_ptr uses in dfp-impl.inc.c (GEN_DFP_T_FPR_I32_Rc).  (Maybe?)