At the moment I can not reproduce this crash.
I don't even find any bug report or any question about the mentioned qt_blend_argb32_on_argb32_sse2 function.

Maybe I did understand something wrong.
I saved a png of size 15x15 but in 24 bit. So one of my questions is, can you please post a 32bit 15x15 png I can use for testing?

But before that... the crash only happened in your program? Or also in your test code?
Because that is not very clear.

If it does not crash in your test code, can you try to completely clean your build? As in removing your build dir or removing the Makefile and object files. Then rerun qmake and make again. Does this solve the problem?

If not, then there might be something wrong elsewhere.
Can you put in some breakpoints and try some debugging?