Yes, FreeBSD is stuck on GCC 4.2.1 for the system compiler right now, as it is the last GPLv2 version. In general I'd think it's beneficial for the kFreeBSD project to use the same compiler (for building the kernel) as the FreeBSD project does, no?
It would be easier, but it is not possible, as gcc-4.2 will not be shipped with squeeze release. I did some more test. Variant with some added gcc switches (-fno-toplevel-reorder -fno-delete-null-pointer-checks)gcc-4.4 -c -O2 -frename-registers -pipe -fno-strict-aliasing -std=c99 -nostdinc -I. -I../../.. -I../../../contrib/altq -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000 -fno-stack-protector -fno-toplevel-reorder -Wstrict-overflow=5 -fno-delete-null-pointer-checks -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mfpmath=387 -mno-sse -mno-sse2 -mno-sse3 -mno-mmx -mno-3dnow -msoft-float -fno-asynchronous-unwind-tables -ffreestanding
fails (panic in swapper) similarly also for me. But when compiled with "-O1" it boots (and runs) fine on kfreebsd-amd64.gcc-4.4 -c -O1 -frename-registers -pipe -std=c99 -nostdinc -I. -I../../.. -I../../../contrib/altq -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000 -fno-stack-protector -fno-toplevel-reorder -Wstrict-overflow=5 -fno-delete-null-pointer-checks -fno-omit-frame-pointer -mcmodel=kernel -mno-red-zone -mfpmath=387 -mno-sse -mno-sse2 -mno-sse3 -mno-mmx -mno-3dnow -msoft-float -fno-asynchronous-unwind-tables -ffreestanding
ii binutils 2.20.1-14 ii gcc-4.4 4.4.4-14 Petr