Current Minimal Binary Size
Andrew Jeffery
andrew at aj.id.au
Tue Sep 17 10:49:28 AEST 2019
Hi Wilfred,
On Mon, 16 Sep 2019, at 23:40, Wilfred Smith wrote:
> >
> > Out of curiosity, how are you generating these results? For instance using
> > the Ubuntu ARM GCC cross compiler I have a smallest executable of less
> > than half the size of what you list above:
> >
> > $ arm-linux-gnueabi-gcc --version
> > arm-linux-gnueabi-gcc (Ubuntu/Linaro 8.3.0-6ubuntu1) 8.3.0
> > Copyright (C) 2018 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions. There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> >
> > $ cat empty.c
> > int main(void)
> > {
> > return 0;
> > }
> > $ make empty CC=arm-linux-gnueabi-gcc CFLAGS=-Os && arm-linux-gnueabi-strip empty && ls -l empty
> > arm-linux-gnueabi-gcc -Os -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed empty.c -o empty
> > -rwxr-xr-x 1 andrew andrew 5544 Sep 16 13:08 empty
> > $ size empty
> > text data bss dec hex filename
> > 759 276 4 1039 40f empty
> >
> > Admittedly it's not the SDK cross-compiler, but some more clarity
> > on how you came to those numbers would be helpful.
> >
> > Andrew
> >
>
> Andrew,
>
> So glad you replied.
>
> I’m doing a Bitbake build for a recipe that uses CMAKE:
>
> add_executable( sizetest.bin source/sizebin.cpp)
> target_compile_options( sizetest.bin PUBLIC -Os -s)
>
> I don’t know if it matters, but I’m compiling in CentOS 7 with the
> OpenBMC/OpenBMC tree and my TemplateConf set to
> meta-facebook/meta-tiogapass.
>
> arm-openbmc-linux-gnueabi-gcc (GCC) 9.2.0
>
> I need to run an errand this morning, but will replicate your precise
> sequence a bit later today.
>
> I’m always open to the possibility that I’m doing something wrong or
> missing something, but last time I checked, -Os generates the smallest
> possible code and -s strips symbols.
Okay. Maybe :) Here are some results. The summary is that there's no
real benefit to -Ox for x > 0 for your test cases beyond a slight saving
for the iostream case, because there's effectively no code to optimise.
Not stripped vs stripped contributes the biggest change as expected,
and it looks like your results are may not have been stripped.
$ ls -l *.O?*
-rwxr-xr-x 1 andrew andrew 12068 Sep 17 10:10 iostream.O0
-rwxr-xr-x 1 andrew andrew 5588 Sep 17 10:10 iostream.O0.stripped
-rwxr-xr-x 1 andrew andrew 11848 Sep 17 10:10 iostream.O1
-rwxr-xr-x 1 andrew andrew 5540 Sep 17 10:10 iostream.O1.stripped
-rwxr-xr-x 1 andrew andrew 11848 Sep 17 10:10 iostream.O2
-rwxr-xr-x 1 andrew andrew 5540 Sep 17 10:10 iostream.O2.stripped
-rwxr-xr-x 1 andrew andrew 11848 Sep 17 10:10 iostream.O3
-rwxr-xr-x 1 andrew andrew 5540 Sep 17 10:10 iostream.O3.stripped
-rwxr-xr-x 1 andrew andrew 11848 Sep 17 10:10 iostream.Os
-rwxr-xr-x 1 andrew andrew 5540 Sep 17 10:10 iostream.Os.stripped
-rwxr-xr-x 1 andrew andrew 11308 Sep 17 10:10 printf.O0
-rwxr-xr-x 1 andrew andrew 5528 Sep 17 10:10 printf.O0.stripped
-rwxr-xr-x 1 andrew andrew 11308 Sep 17 10:10 printf.O1
-rwxr-xr-x 1 andrew andrew 5528 Sep 17 10:10 printf.O1.stripped
-rwxr-xr-x 1 andrew andrew 11308 Sep 17 10:10 printf.O2
-rwxr-xr-x 1 andrew andrew 5528 Sep 17 10:10 printf.O2.stripped
-rwxr-xr-x 1 andrew andrew 11308 Sep 17 10:10 printf.O3
-rwxr-xr-x 1 andrew andrew 5528 Sep 17 10:10 printf.O3.stripped
-rwxr-xr-x 1 andrew andrew 11308 Sep 17 10:10 printf.Os
-rwxr-xr-x 1 andrew andrew 5528 Sep 17 10:10 printf.Os.stripped
-rwxr-xr-x 1 andrew andrew 11240 Sep 17 10:10 return.O0
-rwxr-xr-x 1 andrew andrew 5524 Sep 17 10:10 return.O0.stripped
-rwxr-xr-x 1 andrew andrew 11240 Sep 17 10:10 return.O1
-rwxr-xr-x 1 andrew andrew 5524 Sep 17 10:10 return.O1.stripped
-rwxr-xr-x 1 andrew andrew 11240 Sep 17 10:10 return.O2
-rwxr-xr-x 1 andrew andrew 5524 Sep 17 10:10 return.O2.stripped
-rwxr-xr-x 1 andrew andrew 11240 Sep 17 10:10 return.O3
-rwxr-xr-x 1 andrew andrew 5524 Sep 17 10:10 return.O3.stripped
-rwxr-xr-x 1 andrew andrew 11240 Sep 17 10:10 return.Os
-rwxr-xr-x 1 andrew andrew 5524 Sep 17 10:10 return.Os.stripped
These results were generated from a patch like:
>From 9661cfd8a299d35c7a834720a537ade62e0637d2 Mon Sep 17 00:00:00 2001
From: Andrew Jeffery <andrew at aj.id.au>
Date: Tue, 17 Sep 2019 10:02:45 +0930
Subject: [PATCH] binsize
Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
---
binsize.bb | 28 ++++++++++++++++++++++++++++
binsize/iostream.cpp | 8 ++++++++
binsize/printf.c | 8 ++++++++
binsize/return.c | 4 ++++
4 files changed, 48 insertions(+)
create mode 100644 binsize.bb
create mode 100644 binsize/iostream.cpp
create mode 100644 binsize/printf.c
create mode 100644 binsize/return.c
diff --git a/binsize.bb b/binsize.bb
new file mode 100644
index 000000000000..9dafc74535f5
--- /dev/null
+++ b/binsize.bb
@@ -0,0 +1,28 @@
+LICENSE = "Apache-2.0"
+LIC_FILES_CHKSUM = "file://${IBMBASE}/COPYING.apache-2.0;md5=34400b68072d710fecd0a2940a0d1658"
+
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+SRC_URI = ""
+SRC_URI += "file://return.c"
+SRC_URI += "file://printf.c"
+SRC_URI += "file://iostream.cpp"
+
+buildit () {
+ OUT="${WORKDIR}/$1"
+ OPT="$2"
+ make CFLAGS=-O${OPT} CXXFLAGS=-O${OPT} ${OUT}
+ cp ${OUT} ${OUT}.O${OPT}.stripped
+ mv ${OUT} ${OUT}.O${OPT}
+ arm-openbmc-linux-gnueabi-strip ${OUT}.O${OPT}.stripped
+}
+
+do_compile () {
+
+ for app in 'return' 'printf' 'iostream'
+ do
+ for O in 0 1 2 3 s
+ do
+ buildit "$app" $O
+ done
+ done
+}
diff --git a/binsize/iostream.cpp b/binsize/iostream.cpp
new file mode 100644
index 000000000000..2595edcd4953
--- /dev/null
+++ b/binsize/iostream.cpp
@@ -0,0 +1,8 @@
+#include <iostream>
+
+int main(int argc, const char *argv[])
+{
+ std::cout << argv[0] << "\n";
+
+ return 0;
+}
diff --git a/binsize/printf.c b/binsize/printf.c
new file mode 100644
index 000000000000..841a1460ae54
--- /dev/null
+++ b/binsize/printf.c
@@ -0,0 +1,8 @@
+#include <stdio.h>>
+
+int main(int argc, const char *argv[])
+{
+ printf("%s", argv[0]);
+
+ return 0;
+}
diff --git a/binsize/return.c b/binsize/return.c
new file mode 100644
index 000000000000..31dbf45bf99c
--- /dev/null
+++ b/binsize/return.c
@@ -0,0 +1,4 @@
+int main(void)
+{
+ return 0;
+}
--
2.20.1
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