compiling the GNU compiler sources for 64-bit is not that easy, the same is for compiling as a cross-compiler 32bit/64bit.
It took me a few days and finally I gave up.
I took the binary version for testing: http://tdm-gcc.tdragon.net.
Using a 64bit compiler lead to much trouble as I forgot that a 64bit compiler comes with different size of types :-)
However, I am compiling perl modules for perl on Windows 7 (64bit system) with a 32bit compiler and didn't faced any problems so far.
I have also tested 64bit perl versions and I have come to the point
that there are not as much perl modules available as in the standard installation.
In example the Win32::SerilPort module was not available for 64bit (at that time).
Compiling modules designed for 32bit with 64bit compiler is also leading to an shouting compiler.
So is a 64bit compiler really needed?
Yet I have not tested the Microsoft nmake tool chain with 64bit option, might by worth giving a try.
IMHO modules are best installed with the given maintenance tools of ActiveState or Strawberry.
By manual installation you have to take care for version dependencies for yourself - this is no fun ;-)