musl: Add mimalloc as a possible malloc implementation

Add mimalloc as an alternative malloc implementation and use it. This closes glibc's malloc performance advantage over musl and in some situations makes more efficient use of memory.

In testing, mimalloc outperformed mallocng, jemalloc and dlmalloc. Not yet tested: Bionic malloc

Signed-off-by: Bernhard Rosenkränzer bernhard.rosenkraenzer.ext@huawei.com

meta-oniro-staging/recipes-core/musl/musl/import-mimalloc.sh

+#!/bin/sh
+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Import mimalloc into the musl tree as an alternative to
+# oldmalloc and mallocng
+if [ -z "$1" ]; then
+	echo "Usage: $0 /path/to/mimalloc"
+	echo "	Where /path/to/mimalloc is the path to the mimalloc source,"
+	echo "	with the tag/branch you want to import already checked out."
+	exit 1
+fi
+cd "$(realpath $(dirname $0))"
+cp "$1"/src/* "$1"/include/* .
+# We don't need the overrides, given we're system malloc
+rm alloc-override*
+sed -i -e '/alloc-override.c/d' alloc.c
+# Name functions the way musl likes it
+# glue code must come after mimalloc.h because
+# of __attribute__((malloc))
+sed -i -e '/mimalloc.h/a#include "glue.h"' alloc.c
+sed -i -e '/mimalloc.h/i#include "glue.h"' alloc-aligned.c alloc-posix.c heap.c
+# page-queue.c is supposed to be #included by page.c and not
+# built standalone (but musl's build system builds $MALLOC/*.c)
+mv page-queue.c page-queue.inc
+sed -i -e 's,page-queue.c,page-queue.inc,' page.c
+# musl's define weak clashes with mimalloc's use of
+# __attribute((weak))
+sed -i -e 's,__attribute((weak)),weak,g' *.c
+# This seems to be obsolete -- not referenced in mimalloc's
+# CMake files and not included by anything
+rm region.c
+# Helper for including mimalloc into a project. Not useful
+# in our context.
+rm static.c
+# musl aligned_alloc() is the same as mimalloc's mi_malloc_aligned... but
+# with parameters reversed
+cat >>alloc.c <<EOF
+void *aligned_alloc(size_t align, size_t len) {
+	return mi_malloc_aligned(len, align);
+}
+EOF
+# FIXME malloc_donate() is currently not implemented for mimalloc. Implement a
+# stub so ldso doesn't freak out, but it would be nice to implement this
+# properly to allow reclaiming the wasted space from shared libraries...
+cat >>alloc.c <<EOF
+void __malloc_donate(char *start, char *end) {
+}
+EOF