<div dir="ltr">What is "frep.x86.sse2.sqrt.pd". I'm only familiar with things prefixed with "llvm.x86".</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jul 18, 2013 at 10:12 PM, Peter Newman <span dir="ltr"><<a href="mailto:peter@uformia.com" target="_blank">peter@uformia.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>After stepping through the produced
assembly, I believe I have a culprit.<br>
<br>
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.<br>
<br>
Peter N<div><div class="h5"><br>
<br>
On 19/07/2013 2:09 PM, Peter Newman wrote:<br>
</div></div></div><div><div class="h5">
<blockquote type="cite">
<div>I've attached the module->dump()
that our code is producing. Unfortunately this is the smallest
test case I have available.<br>
<br>
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.<br>
<br>
The function in module-dump.ll (called crashfunc in this file)
is called with<br>
- func_params 0x0018f3b0 double [3]<br>
[0x0] -11.339976634695301 double<br>
[0x1] -9.7504239056205506 double<br>
[0x2] -5.2900856817382804 double<br>
at the time of the exception.<br>
<br>
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 ) ).<br>
<br>
Hopefully this is reproducible for you.<br>
<br>
--<br>
PeterN<br>
<br>
On 18/07/2013 4:37 PM, Craig Topper wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Are you able to send any IR for others to
reproduce this issue?</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Wed, Jul 17, 2013 at 11:23 PM,
Peter Newman <span dir="ltr"><<a href="mailto:peter@uformia.com" target="_blank">peter@uformia.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">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.<br>
<br>
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 .<br>
<br>
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.<br>
<br>
I'm going to dig through the passes controlled by that
parameter and see if I can narrow down which optimization
is causing it.<br>
<br>
Peter N
<div>
<div><br>
<br>
On 17/07/2013 1:58 PM, Solomon Boulos wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
As someone off list just told me, perhaps my new bug
is the same issue:<br>
<br>
<a href="http://llvm.org/bugs/show_bug.cgi?id=16640" target="_blank">http://llvm.org/bugs/show_bug.cgi?id=16640</a><br>
<br>
Do you happen to be using FastISel?<br>
<br>
Solomon<br>
<br>
On Jul 16, 2013, at 6:39 PM, Peter Newman <<a href="mailto:peter@uformia.com" target="_blank">peter@uformia.com</a>>
wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hello all,<br>
<br>
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.<br>
<br>
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).<br>
<br>
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.<br>
<br>
The generated instruction varies, but it seems to
often be similar to (I don't have it in front of
me, sorry):<br>
movapd xmm0, xmm[ecx+0x???????]<br>
Where the xmm register changes, and the second
parameter is a memory access.<br>
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.<br>
<br>
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.<br>
<br>
--<br>
Peter N<br>
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<div><br>
</div>
-- <br>
~Craig </div>
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<br>
</div></div></div>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>~Craig
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