Qt 5.3 Might Depend On SSE2 CPUs
Phoronix: Qt 5.3 Might Depend On SSE2 CPUs
Thiago Macieira of Intel is coordinating a proposal to enable SSE2 by default for the 32-bit builds of the Qt tool-kit beginning with the Qt 5.3 release. This likely change is due to the V4 JIT engine generating floating-point math for Qt's QML only using SSE x86 registers...
Before everyone freaks out
Distros can just compile Qt to allow older processors. This only affects people who download the binaries straight from the Qt website.