I just tried to compile Linux kernel version 2.6.18.2 with gcc-4.3-20061118 snapshot on a x86_64 box.
The compiler said /home/dcb/gnu/43-20061118/results/bin/gcc -g -O3 -Wall -march=opteron -Wp,-MD,arch/x86_64/lib/.csum-partial.o.d -nostdinc -isystem /home/dcb/gnu/43-20061118/results/lib/gcc/x86_64-unknown-linux-gnu/4.3.0/include -D__KERNEL__ -Iinclude -include include/linux/autoconf.h -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Os -m64 -mno-red-zone -mcmodel=kernel -pipe -fno-reorder-blocks -Wno-sign-compare -funit-at-a-time -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -fno-omit-frame-pointer -fno-optimize-sibling-calls -fasynchronous-unwind-tables -g -fno-stack-protector -Wdeclaration-after-statement -Wno-pointer-sign -funroll-loops -ffunction-sections -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(csum_partial)" -D"KBUILD_MODNAME=KBUILD_STR(csum_partial)" -c -o arch/x86_64/lib/.tmp_csum-partial.o arch/x86_64/lib/csum-partial.c arch/x86_64/lib/csum-partial.c: In function 'csum_partial': arch/x86_64/lib/csum-partial.c:138: error: verify_flow_info: Block 29 has loop_father, but there are no loops arch/x86_64/lib/csum-partial.c:138: error: verify_flow_info: Block 28 has loop_father, but there are no loops Preprocessed source code attached. Flags -Os -funroll-loops required. If it is any help, this code worked fine in gcc snapshot 4.3-20051111 -- Summary: ice for legal code Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: dcb314 at hotmail dot com GCC host triplet: x86_64_linux_suse http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29895