Intel® 64 and IA-32 Architectures Optimization Reference Manual

STACK ALIGNMENTD.2 INLINED ASSEMBLY AND EBXWhen using aligned frames, the EBX register generally should not be modified ininlined assembly blocks since EBX is used to keep track of the argument block.Programmers may modify EBX only if they do not need to access the arguments andprovided they save EBX and restore it before the end of the function (since ESP isrestored relative to EBX in the function’s epilog).NOTEDo not use the EBX register in inline assembly functions that usedynamic stack alignment for double, __m64, and __m128 localvariables unless you save and restore EBX each time you use it. TheIntel C++ Compiler uses the EBX register to control alignment ofvariables of these types, so the use of EBX, without preserving it, willcause unexpected program execution.D-7