[LLVMdev] fptoui calling a function that modifies ECX
Craig Topper
craig.topper at gmail.com
Fri Jul 19 00:45:09 PDT 2013
I don't think that's going to work.
On Fri, Jul 19, 2013 at 12:24 AM, Peter Newman <peter at uformia.com> wrote:
> Thank you, I'm trying this now.
>
>
> On 19/07/2013 5:23 PM, Craig Topper wrote:
>
> Try adding ECX to the Defs of this part of
> lib/Target/X86/X86InstrCompiler.td like I've done below. I don't have a
> Windows machine to test myself.
>
> let Defs = [EAX, EDX, ECX, EFLAGS], FPForm = SpecialFP in {
> def WIN_FTOL_32 : I<0, Pseudo, (outs), (ins RFP32:$src),
> "# win32 fptoui",
> [(X86WinFTOL RFP32:$src)]>,
> Requires<[In32BitMode]>;
>
> def WIN_FTOL_64 : I<0, Pseudo, (outs), (ins RFP64:$src),
> "# win32 fptoui",
> [(X86WinFTOL RFP64:$src)]>,
> Requires<[In32BitMode]>;
> }
>
>
> On Thu, Jul 18, 2013 at 11:59 PM, Peter Newman <peter at uformia.com> wrote:
>
>> Oh, excellent point, I agree. My bad. Now that I'm not assuming those
>> are the sqrt, I see the sqrtpd's in the output. Also there are three
>> fptoui's and there are 3 call instances.
>>
>> (Changing subject line again.)
>>
>> Now it looks like it's bug #13862
>>
>> On 19/07/2013 4:51 PM, Craig Topper wrote:
>>
>> I think those calls correspond to this
>>
>> %110 = fptoui double %109 to i32
>>
>> The calls are followed by an imul with 12 which matches up with what
>> occurs right after the fptoui in the IR.
>>
>>
>> On Thu, Jul 18, 2013 at 11:48 PM, Peter Newman <peter at uformia.com> wrote:
>>
>>> Yes, that is the result of module-dump.ll
>>>
>>>
>>> On 19/07/2013 4:46 PM, Craig Topper wrote:
>>>
>>> Does this correspond to one of the .ll files you sent earlier?
>>>
>>>
>>> On Thu, Jul 18, 2013 at 11:34 PM, Peter Newman <peter at uformia.com>wrote:
>>>
>>>> (Changing subject line as diagnosis has changed)
>>>>
>>>> I'm attaching the compiled code that I've been getting, both with
>>>> CodeGenOpt::Default and CodeGenOpt::None . The crash isn't occurring with
>>>> CodeGenOpt::None, but that seems to be because ECX isn't being used - it
>>>> still gets set to 0x7fffffff by one of the calls to 76719BA1
>>>>
>>>> I notice that X86::SQRTPD[m|r] appear in
>>>> X86InstrInfo::isHighLatencyDef. I was thinking an optimization might be
>>>> removing it, but I don't get the sqrtpd instruction even if the createJIT
>>>> optimization level turned off.
>>>>
>>>> I am trying this with the Release 3.3 code - I'll try it with trunk and
>>>> see if I get a different result there. Maybe there was a recent commit for
>>>> this.
>>>>
>>>> --
>>>> Peter N
>>>>
>>>> On 19/07/2013 4:00 PM, Craig Topper wrote:
>>>>
>>>> Hmm, I'm not able to get those .ll files to compile if I disable SSE
>>>> and I end up with SSE instructions(including sqrtpd) if I don't disable it.
>>>>
>>>>
>>>> On Thu, Jul 18, 2013 at 10:53 PM, Peter Newman <peter at uformia.com>wrote:
>>>>
>>>>> Is there something specifically required to enable SSE? If it's not
>>>>> detected as available (based from the target triple?) then I don't think we
>>>>> enable it specifically.
>>>>>
>>>>> Also it seems that it should handle converting to/from the vector
>>>>> types, although I can see it getting confused about needing to do that if
>>>>> it thinks SSE isn't available at all.
>>>>>
>>>>>
>>>>> On 19/07/2013 3:47 PM, Craig Topper wrote:
>>>>>
>>>>> Hmm, maybe sse isn't being enabled so its falling back to emulating
>>>>> sqrt?
>>>>>
>>>>>
>>>>> On Thu, Jul 18, 2013 at 10:45 PM, Peter Newman <peter at uformia.com>wrote:
>>>>>
>>>>>> In the disassembly, I'm seeing three cases of
>>>>>> call 76719BA1
>>>>>>
>>>>>> I am assuming this is the sqrt function as this is the only function
>>>>>> called in the LLVM IR.
>>>>>>
>>>>>> The code at 76719BA1 is:
>>>>>>
>>>>>> 76719BA1 push ebp
>>>>>> 76719BA2 mov ebp,esp
>>>>>> 76719BA4 sub esp,20h
>>>>>> 76719BA7 and esp,0FFFFFFF0h
>>>>>> 76719BAA fld st(0)
>>>>>> 76719BAC fst dword ptr [esp+18h]
>>>>>> 76719BB0 fistp qword ptr [esp+10h]
>>>>>> 76719BB4 fild qword ptr [esp+10h]
>>>>>> 76719BB8 mov edx,dword ptr [esp+18h]
>>>>>> 76719BBC mov eax,dword ptr [esp+10h]
>>>>>> 76719BC0 test eax,eax
>>>>>> 76719BC2 je 76719DCF
>>>>>> 76719BC8 fsubp st(1),st
>>>>>> 76719BCA test edx,edx
>>>>>> 76719BCC js 7671F9DB
>>>>>> 76719BD2 fstp dword ptr [esp]
>>>>>> 76719BD5 mov ecx,dword ptr [esp]
>>>>>> 76719BD8 add ecx,7FFFFFFFh
>>>>>> 76719BDE sbb eax,0
>>>>>> 76719BE1 mov edx,dword ptr [esp+14h]
>>>>>> 76719BE5 sbb edx,0
>>>>>> 76719BE8 leave
>>>>>> 76719BE9 ret
>>>>>>
>>>>>>
>>>>>> As you can see at 76719BD5, it modifies ECX .
>>>>>>
>>>>>> I don't know that this is the sqrtpd function (for example, I'm not
>>>>>> seeing any SSE instructions here?) but whatever it is, it's being called
>>>>>> from the IR I attached earlier, and is modifying ECX under some
>>>>>> circumstances.
>>>>>>
>>>>>>
>>>>>> On 19/07/2013 3:29 PM, Craig Topper wrote:
>>>>>>
>>>>>> That should map directly to sqrtpd which can't modify ecx.
>>>>>>
>>>>>>
>>>>>> On Thu, Jul 18, 2013 at 10:27 PM, Peter Newman <peter at uformia.com>wrote:
>>>>>>
>>>>>>> Sorry, that should have been llvm.x86.sse2.sqrt.pd
>>>>>>>
>>>>>>>
>>>>>>> On 19/07/2013 3:25 PM, Craig Topper wrote:
>>>>>>>
>>>>>>> What is "frep.x86.sse2.sqrt.pd". I'm only familiar with things
>>>>>>> prefixed with "llvm.x86".
>>>>>>>
>>>>>>>
>>>>>>> On Thu, Jul 18, 2013 at 10:12 PM, Peter Newman <peter at uformia.com>wrote:
>>>>>>>
>>>>>>>> After stepping through the produced assembly, I believe I have a
>>>>>>>> culprit.
>>>>>>>>
>>>>>>>> One of the calls to @frep.x86.sse2.sqrt.pd is modifying the value
>>>>>>>> of ECX - while the produced code is expecting it to still contain its
>>>>>>>> previous value.
>>>>>>>>
>>>>>>>> Peter N
>>>>>>>>
>>>>>>>>
>>>>>>>> On 19/07/2013 2:09 PM, Peter Newman wrote:
>>>>>>>>
>>>>>>>> I've attached the module->dump() that our code is producing.
>>>>>>>> Unfortunately this is the smallest test case I have available.
>>>>>>>>
>>>>>>>> This is before any optimization passes are applied. There are two
>>>>>>>> separate modules in existence at the time, and there are no guarantees
>>>>>>>> about the order the surrounding code calls those functions, so there may be
>>>>>>>> some interaction between them? There shouldn't be, they don't refer to any
>>>>>>>> common memory etc. There is no multi-threading occurring.
>>>>>>>>
>>>>>>>> The function in module-dump.ll (called crashfunc in this file) is
>>>>>>>> called with
>>>>>>>> - func_params 0x0018f3b0 double [3]
>>>>>>>> [0x0] -11.339976634695301 double
>>>>>>>> [0x1] -9.7504239056205506 double
>>>>>>>> [0x2] -5.2900856817382804 double
>>>>>>>> at the time of the exception.
>>>>>>>>
>>>>>>>> This is compiled on a "i686-pc-win32" triple. All of the
>>>>>>>> non-intrinsic functions referred to in these modules are the standard
>>>>>>>> equivalents from the MSVC library (e.g. @asin is the standard C lib
>>>>>>>> double asin( double ) ).
>>>>>>>>
>>>>>>>> Hopefully this is reproducible for you.
>>>>>>>>
>>>>>>>> --
>>>>>>>> PeterN
>>>>>>>>
>>>>>>>> On 18/07/2013 4:37 PM, Craig Topper wrote:
>>>>>>>>
>>>>>>>> Are you able to send any IR for others to reproduce this issue?
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wed, Jul 17, 2013 at 11:23 PM, Peter Newman <peter at uformia.com>wrote:
>>>>>>>>
>>>>>>>>> Unfortunately, this doesn't appear to be the bug I'm hitting. I
>>>>>>>>> applied the fix to my source and it didn't make a difference.
>>>>>>>>>
>>>>>>>>> Also further testing found me getting the same behavior with other
>>>>>>>>> SIMD instructions. The common factor is in each case, ECX is set to
>>>>>>>>> 0x7fffffff, and it's an operation using xmm ptr ecx+offset .
>>>>>>>>>
>>>>>>>>> Additionally, turning the optimization level passed to createJIT
>>>>>>>>> down appears to avoid it, so I'm now leaning towards a bug in one of the
>>>>>>>>> optimization passes.
>>>>>>>>>
>>>>>>>>> I'm going to dig through the passes controlled by that parameter
>>>>>>>>> and see if I can narrow down which optimization is causing it.
>>>>>>>>>
>>>>>>>>> Peter N
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 17/07/2013 1:58 PM, Solomon Boulos wrote:
>>>>>>>>>
>>>>>>>>>> As someone off list just told me, perhaps my new bug is the same
>>>>>>>>>> issue:
>>>>>>>>>>
>>>>>>>>>> http://llvm.org/bugs/show_bug.cgi?id=16640
>>>>>>>>>>
>>>>>>>>>> Do you happen to be using FastISel?
>>>>>>>>>>
>>>>>>>>>> Solomon
>>>>>>>>>>
>>>>>>>>>> On Jul 16, 2013, at 6:39 PM, Peter Newman <peter at uformia.com>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>> Hello all,
>>>>>>>>>>>
>>>>>>>>>>> I'm currently in the process of debugging a crash occurring in
>>>>>>>>>>> our program. In LLVM 3.2 and 3.3 it appears that JIT generated code is
>>>>>>>>>>> attempting to perform access unaligned memory with a SSE2 instruction.
>>>>>>>>>>> However this only happens under certain conditions that seem (but may not
>>>>>>>>>>> be) related to the stacks state on calling the function.
>>>>>>>>>>>
>>>>>>>>>>> Our program acts as a front-end, using the LLVM C++ API to
>>>>>>>>>>> generate a JIT generated function. This function is primarily mathematical,
>>>>>>>>>>> so we use the Vector types to take advantage of SIMD instructions (as well
>>>>>>>>>>> as a few SSE2 intrinsics).
>>>>>>>>>>>
>>>>>>>>>>> This worked in LLVM 2.8 but started failing in 3.2 and has
>>>>>>>>>>> continued to fail in 3.3. It fails with no optimizations applied to the
>>>>>>>>>>> LLVM Function/Module. It crashes with what is reported as a memory access
>>>>>>>>>>> error (accessing 0xffffffff), however it's suggested that this is how the
>>>>>>>>>>> SSE fault raising mechanism appears.
>>>>>>>>>>>
>>>>>>>>>>> The generated instruction varies, but it seems to often be
>>>>>>>>>>> similar to (I don't have it in front of me, sorry):
>>>>>>>>>>> movapd xmm0, xmm[ecx+0x???????]
>>>>>>>>>>> Where the xmm register changes, and the second parameter is a
>>>>>>>>>>> memory access.
>>>>>>>>>>> ECX is always set to 0x7ffffff - however I don't know if this is
>>>>>>>>>>> part of the SSE error reporting process or is part of the situation causing
>>>>>>>>>>> the error.
>>>>>>>>>>>
>>>>>>>>>>> I haven't worked out exactly what code path etc is causing this
>>>>>>>>>>> crash. I'm hoping that someone can tell me if there were any changed
>>>>>>>>>>> requirements for working with SIMD in LLVM 3.2 (or earlier, we haven't
>>>>>>>>>>> tried 3.0 or 3.1). I currently suspect the use of GlobalVariable (we first
>>>>>>>>>>> discovered the crash when using a feature that uses them), however I have
>>>>>>>>>>> attempted using setAlignment on the GlobalVariables without any change.
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> Peter N
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> LLVM Developers mailing list
>>>>>>>>>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
>>>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> LLVM Developers mailing list
>>>>>>>>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> ~Craig
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> ~Craig
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> ~Craig
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> ~Craig
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> ~Craig
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> ~Craig
>>>
>>>
>>>
>>
>>
>> --
>> ~Craig
>>
>>
>>
>
>
> --
> ~Craig
>
>
>
--
~Craig
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