The windows X86 compilers (and maybe amd64 too) documents /O1 as reducing size. Regardless of what hotspot uses, the rest of the j2se might benefit from a footprint reduction of the dlls if /01 is used over /O2. Builds and alacrity runs may be necessary. Windows amd64 might have the same issue, but that's typically a server class machine and speed may be more important there.

At the same time, it might be interesting to use /Oy- so that all the X86 code has the frame pointer register used as a frame pointer instead of being used as a general purpose register. There is a concern that this optimization might be needed to keep performance numbers up on X86, but I don't think builds with /Oy- have ever been tried. The Solaris and Linux builds use -xregs=no%frameptr and -fno-omit-frame-pointer which is the functional equivalent of windows /Oy-. Without this frame pointer, serviceability and debugability usually suffers, so even if this is a slight performance loss, it still might be worth it.