Intel ARCHITECTURE IA-32 - Manual (Page 546)

IA-32 Intel® Architecture Optimization
D-10
Inlined Assembly and ebx
When using aligned frames, the ebx register generally should not be
modified in inlined 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 and provided they save ebx and restore it
before the end of the function (since esp is restored relative to ebx in the
function’s epilog).
For additional information on the use of ebx in inline assembly code and
other related issues, see relevant application notes in the Intel
Architecture Performance Training Center.
CAUTION. Do not use the ebx register in inline
assembly functions that use dynamic stack alignment
for double, __m64, and __m128 local variables unless
you save and restore
ebx each time you use it. The
Intel C++ Compiler uses the ebx register to control
alignment of variables of these types, so the use of ebx ,
without preserving it, will cause unexpected program
execution.