+# When bootstrapping with GCC, build stage 1 in C++98 mode to ensure that a
+# C++98 compiler can still start the bootstrap.
+if test "$enable_bootstrap:$GXX" = "yes:yes"; then
+ CXX="$CXX -std=gnu++98"
+fi
+
+AC_ARG_ENABLE([pgo-build],
+[AS_HELP_STRING([--enable-pgo-build[[=lto]]],
+ [enable the PGO build])],
+[enable_pgo_build=$enableval],
+[enable_pgo_build=no])
+
+# Issue errors and warnings for invalid/strange PGO build combinations.
+case "$have_compiler:$host:$target:$enable_pgo_build" in
+ *:*:*:no) ;;
+
+ # Allow the PGO build only if we aren't building a compiler and
+ # we are in a native configuration.
+ no:$build:$build:yes | no:$build:$build:lto) ;;
+
+ # Disallow the PGO bootstrap if we are building a compiler.
+ yes:*:*:yes | yes:*:*:lto)
+ AC_MSG_ERROR([cannot perform the PGO bootstrap when building a compiler]) ;;
+
+ *)
+ AC_MSG_ERROR([invalid option for --enable-pgo-build])
+ ;;
+esac
+
+if test "$enable_pgo_build" != "no"; then
+ AC_MSG_CHECKING([whether the compiler supports -fprofile-generate])
+ old_CFLAGS="$CFLAGS"
+ PGO_BUILD_GEN_CFLAGS="-fprofile-generate"
+ CFLAGS="$CFLAGS $PGO_BUILD_CFLAGS"
+ AC_COMPILE_IFELSE([AC_LANG_SOURCE([int foo;])],,
+ [PGO_BUILD_GEN_CFLAGS=])
+ CFLAGS="$old_CFLAGS"
+ if test -n "$PGO_BUILD_GEN_CFLAGS"; then
+ AC_MSG_RESULT([yes])
+ PGO_BUILD_USE_CFLAGS="-fprofile-use"
+ else
+ AC_MSG_RESULT([no])
+ AC_MSG_ERROR([cannot perform the PGO build without -fprofile-generate])
+ fi
+
+ if test "$enable_pgo_build" = "lto"; then
+ AC_MSG_CHECKING([whether the compiler supports -flto=jobserver -ffat-lto-objects])
+ old_CFLAGS="$CFLAGS"
+ PGO_BUILD_LTO_CFLAGS="-flto=jobserver -ffat-lto-objects"
+ CFLAGS="$CFLAGS $PGO_BUILD_LTO_CFLAGS"
+ AC_COMPILE_IFELSE([AC_LANG_SOURCE([int foo;])],,
+ [PGO_BUILD_LTO_CFLAGS=])
+ CFLAGS="$old_CFLAGS"
+ if test -n "$PGO_BUILD_LTO_CFLAGS"; then
+ AC_MSG_RESULT([yes])
+ else
+ AC_MSG_RESULT([no])
+ AC_MSG_WARN([LTO is disabled for the PGO build])
+ fi
+ fi
+fi
+AC_SUBST(PGO_BUILD_GEN_CFLAGS)
+AC_SUBST(PGO_BUILD_USE_CFLAGS)
+AC_SUBST(PGO_BUILD_LTO_CFLAGS)
+