Re: Recent TCG commit breaks PPC

[Philippe Mathieu-Daudé]

On 1/16/21 8:46 PM, BALATON Zoltan wrote:
> On Sat, 16 Jan 2021, Richard Henderson wrote:
>> On 1/16/21 4:38 AM, BALATON Zoltan wrote:
>>>
>>> Commit 8fe35e0444be (tcg/optimize: Use tcg_constant_internal with
>>> constant
>>> folding) seems to break PPC emulation for me:
>>>
>>> Thread 3 "qemu-system-ppc" received signal SIGSEGV, Segmentation fault.
>>> [Switching to Thread 0x7ffff51e7700 (LWP 22636)]
>>> 0x0000555555afd4ee in ts_are_copies (ts2=0x7fff8c008f90,
>>> ts1=0x7fff8c001510) at
>>> ../tcg/optimize.c:68
>>> 68        return ts_info(ts)->next_copy != ts;
>>
>> I don't replicate this assertion.
>>
>> Interestingly, I replicate a different assertion:
>>
>> qemu-system-ppc: ../qemu/tcg/tcg.c:1210: tcg_temp_alloc: Assertion `n
>> < 512'
>> failed.
>> Aborted (core dumped)
>>
>> What compiler version(s) are you guys using?
> 
> With --enable-debug (that I don't normally use because it makes PPC
> emulation too slow) I get the same assertion:
> 
> qemu-system-ppc: ../tcg/tcg.c:1210: tcg_temp_alloc: Assertion `n < 512'
> failed.
> 
> Thread 3 "qemu-system-ppc" received signal SIGABRT, Aborted.
> 
> (gdb) bt
> #0  0x00007ffff6b29a7a in raise () at /lib64/libc.so.6
> #1  0x00007ffff6b12524 in abort () at /lib64/libc.so.6
> #2  0x00007ffff6b1240f in _nl_load_domain.cold.0 () at /lib64/libc.so.6
> #3  0x00007ffff6b1e9a2 in  () at /lib64/libc.so.6
> #4  0x0000555555c5e7a6 in tcg_temp_alloc (s=0x7fff50000b60) at
> tcg/tcg.c:1210
> #5  0x0000555555c5efcb in tcg_constant_internal (type=TCG_TYPE_I32,
> val=-7401584) at tcg/tcg.c:1436
> #6  0x0000555555c7f921 in tcg_opt_gen_movi
>     (s=0x7fff50000b60, temps_used=0x7ffff51e94c0, op=0x7fff505d6308,
> dst=140734535570720, val=18446744073702150032)
>     at tcg/optimize.c:247
> #7  0x0000555555c81e4b in tcg_optimize (s=0x7fff50000b60) at
> tcg/optimize.c:1178
> #8  0x0000555555c6580a in tcg_gen_code (s=0x7fff50000b60,
> tb=0x7fffb3181a00) at tcg/tcg.c:4490
> #9  0x0000555555c34f9c in tb_gen_code (cpu=0x5555567851e0,
> pc=4287582720, cs_base=0, flags=24576, cflags=-16777216)
>     at accel/tcg/translate-all.c:1952
> #10 0x0000555555c79842 in tb_find (cpu=0x5555567851e0, last_tb=0x0,
> tb_exit=0, cf_mask=0) at accel/tcg/cpu-exec.c:454
> #11 0x0000555555c7a109 in cpu_exec (cpu=0x5555567851e0) at
> accel/tcg/cpu-exec.c:810
> #12 0x0000555555c6e906 in tcg_cpus_exec (cpu=0x5555567851e0) at
> accel/tcg/tcg-cpus.c:57
> #13 0x0000555555cbf18e in rr_cpu_thread_fn (arg=0x5555567851e0) at
> accel/tcg/tcg-cpus-rr.c:217
> #14 0x0000555555ea8531 in qemu_thread_start (args=0x5555567c63d0) at
> util/qemu-thread-posix.c:521
> #15 0x00007ffff6cc004c in start_thread () at /lib64/libpthread.so.0
> #16 0x00007ffff6bf13af in clone () at /lib64/libc.so.6
> 
> Previous one was when configuring without --enable-debug, so maybe it
> depends on compiler flags (-O2 vs. -O0).

--debug enables CONFIG_DEBUG_TCG (the n < 512 assertion).