u-boot/scripts/gen_ll_addressable_symbols.sh
Marek Behún c1094987d1 build: support building with Link Time Optimizations
Add plumbing for building U-Boot with Link Time Optimizations.

When building with LTO, $(PLATFORM_LIBS) has to be in --whole-archive /
--no-whole-archive group, otherwise some functions declared in assembly
may not be resolved and linking may fail.

Note: clang may throw away linker list symbols it thinks are unused when
compiling with LTO. To force these symbols to be included, we refer to
them via the __ADDRESSABLE macro in a C file generated from compiled
built-in.o files before linking.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
2021-05-24 14:21:30 -04:00

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#!/bin/bash
# SPDX-License-Identifier: GPL-2.0+
# Copyright (C) 2020 Marek Behún <marek.behun@nic.cz>
# Generate __ADDRESSABLE(symbol) for every linker list entry symbol, so that LTO
# does not optimize these symbols away
set -e
echo '#include <common.h>'
$NM "$@" 2>/dev/null | grep -oe '_u_boot_list_2_[a-zA-Z0-9_]*_2_[a-zA-Z0-9_]*' | \
sort -u | sed -e 's/^\(.*\)/extern char \1[];\n__ADDRESSABLE(\1);/'