[Mingw-notify] [ mingw-Bugs-2967395 ] Crash on sse2 instructions

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Bugs item #2967395, was opened at 2010-03-10 15:12
Message generated for change (Comment added) made by thierryoslo
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Category: gcc
Group: None
>Status: Closed
Resolution: Works For Me
Priority: 5
Private: No
Submitted By: Thierry Bastian (thierryoslo)
Assigned to: Nobody/Anonymous (nobody)
Summary: Crash on sse2 instructions

Initial Comment:
OS: Windows 7 Enterprise 64 bit

Compiler:
Configured with: ../gcc-4.4.0/configure --enable-languages=c,ada,c++,fortran,jav
a,objc,obj-c++ --disable-sjlj-exceptions --enable-shared --enable-libgcj --enabl
e-libgomp --with-dwarf2 --disable-win32-registry --enable-libstdcxx-debug --enab
le-version-specific-runtime-libs --prefix=/mingw --with-gmp=/mingw/src/gmp/root
--with-mpfr=/mingw/src/mpfr/root --build=mingw32
Thread model: win32
gcc version 4.4.0 (GCC)

GNU ld (GNU Binutils) 2.19.1

shell: cmd.exe


To reproduce the problem, run the attached program:
you can simply compile it with gcc -msse2 main.c (avoid optimizations here; since I don't really use the result of the SSE operation they would be optimized away).

If you run it with the debugger (gdb), you'll see it crashes on the last sse2 instruction (_mm_andnot_si128) for no good reason. This seems to happen when the call to the SSE comes from the Windows callback. Only this SSE instruction seems to cause a problem on our side (even though I haven't tested all of them).

For that reason we had to deactivate SSE2 optimizations in our library (Qt) for mingw.

Note: I would be very interested in a workaround if you have one.


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>Comment By: Thierry Bastian (thierryoslo)
Date: 2010-03-11 11:46

Message:
Great. Thanks for the quick feedback. It looks like finally Qt will be
supporting SSE on mingw.

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Comment By: Danny Smith (dannysmith)
Date: 2010-03-10 21:20

Message:
Add  __attribute__ ((force_align_arg_pointer))  to your definition of 
MyWndProc
like so:

LRESULT CALLBACK 
__attribute__ ((force_align_arg_pointer))
 MyWndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

As it says in the gcc docs:

On the Intel x86, the @code{force_align_arg_pointer} attribute may be
applied to individual function definitions, generating an alternate
prologue and epilogue that realigns the runtime stack if necessary.
This supports mixing legacy codes that run with a 4-byte aligned stack
with modern codes that keep a 16-byte stack for SSE compatibility.

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