https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63933
Bug ID: 63933
Summary: Build stage1 with -O2 during bootstrap if host
compiler is a recent gcc version
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: bootstrap
Assignee: unassigned at gcc dot gnu.org
Reporter: trippels at gcc dot gnu.org
Currently gcc doesn't add any optimization level flags during stage1.
This means that stage1 is build with the default -O0 and that results
in a very slow compiler. Build times during stage2 are very high
because of this.
One solution would be to detect the host compiler and if it is a
recent (maintained?) version of gcc, then build stage1 with -O2.
I did some rough measurements on gcc112:
With:
../gcc/configure --disable-libstdcxx-pch --disable-libvtv --disable-libitm
--disable-libcilkrts --disable-libssp --disable-libgomp --disable-werror
--disable-multilib --enable-languages=c,c++,fortran
I get for the current default:
make -j160 28473.74s user 481.93s system 2067% cpu 23:20.53 total
Adding -O2 during stage1 almost halves the bootstrap time:
make -j160 15233.80s user 446.17s system 1918% cpu 13:37.25 total
