[Bug target/113059] New: [14 regression] fftw fails tests for -O3 -m32 -march=znver2 since r14-6210-ge44ed92dbbe9d4

["sjames at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113059

            Bug ID: 113059
           Summary: [14 regression] fftw fails tests for -O3 -m32
                    -march=znver2 since r14-6210-ge44ed92dbbe9d4
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

fftw started failing tests (very inconsistently - almost always fails, but
sometimes w/ segfault, sometimes with wrong results) since
r14-6210-ge44ed92dbbe9d4.

Might be a continuation of PR112572. We had pinskia's workaround patch applied
until r14-6210-ge44ed92dbbe9d4 landed so I may need to double check.

I can reproduce with the following:
```
./configure CFLAGS="-O3 -m32 -march=znver2 -ggdb3"
make -j$(nproc)
make -j$(nproc) check
```

Just `tests/bench --verbose=1 --verify //obrd896` seems to be a good crasher
for me.

```
Program received signal SIGSEGV, Segmentation fault.
r2cf_32 (R0=0xffff97c0, R1=0xffff98d0, Cr=0xffff97c0, Ci=<optimized out>,
rs=<optimized out>, csr=0x56690040, csi=0x0, v=<optimized out>, ivs=1, ovs=1)
at r2cf_32.c:490
490                         Ci[WS(csi, 8)] = T29 - T28;
(gdb) bt
#0  r2cf_32 (R0=0xffff97c0, R1=0xffff98d0, Cr=0xffff97c0, Ci=<optimized out>,
rs=<optimized out>, csr=0x56690040, csi=0x0, v=<optimized out>, ivs=1, ovs=1)
at r2cf_32.c:490
#1  0x56632963 in dobatch_r2hc (ego=0x566916b0, I=0x56680e80, O=0x56680e80,
buf=0xffff97c0, batchsz=1) at direct-r2c.c:91
#2  0x56632a5d in iterate (ego=0x566916b0, I=<optimized out>, O=<optimized
out>, dobatch=0x56632880 <dobatch_r2hc>) at direct-r2c.c:142
#3  0x565a09f5 in fftw_rdft_solve (ego_=0x566916b0, p_=0x566921d0) at
solve.c:29
#4  0x565603eb in measure (iter=1, p=<optimized out>, pln=<optimized out>) at
timer.c:136
#5  fftw_measure_execution_time (plnr=0x56684690, pln=0x566916b0, p=0x566921d0)
at timer.c:159
#6  0x5655d853 in evaluate_plan (ego=ego@entry=0x56684690,
pln=pln@entry=0x566916b0, p=p@entry=0x566921d0) at planner.c:460
#7  0x5655e773 in search0 (ego=ego@entry=0x56684690, p=p@entry=0x566921d0,
slvndx=slvndx@entry=0xffffbbac, flagsp=<optimized out>) at planner.c:529
#8  0x5655eb37 in search (flagsp=0xffffbbb0, slvndx=0xffffbbac, p=0x566921d0,
ego=0x56684690) at planner.c:600
#9  mkplan (ego=<optimized out>, p=<optimized out>) at planner.c:711
[...]
```

Reducing is challenging so far, as FFTW is massive. I'm not going to waste much
more time on that, but I'll do the usual bisecting object files and such now.