Installing gcc-explorer and setting it up with gcc6809 and cmoc

A recent version of node.js is needed so I recommend Ubuntu 16.04

sudo apt-get install nodejs npm
git clone https://github.com/mattgodbolt/gcc-explorer.git
cd gcc-explorer/
make

(you can now test the stock installation in your browser)
(stop it with ctrl-C)

sudo add-apt-repository ppa:tormodvolden/m6809

echo "deb http://ppa.launchpad.net/tormodvolden/m6809/ubuntu trusty main" | sudo tee -a /etc/apt/sources.list.d/tormodvolden-ubuntu-m6809-xenial.list 

sudo apt-get update
sudo apt-get install gcc6809 lwtools cmoc

Create these two configuration files:

$ cat etc/config/c.defaults.properties
# Default settings for C
compilers=/usr/bin/gcc
defaultCompiler=/usr/bin/gcc
compileFilename=example.c
stubRe=\bmain\b
stubText=int main(void){return 0;/*stub provided by Compiler Explorer*/}

$ cat etc/config/c.local.properties
compilers=gcc6809:cmoc:gcc
compiler.gcc6809.exe=/usr/bin/m6809-unknown-gcc
compiler.gcc6809.name=gcc6809 4.6.4lw
compiler.cmoc.exe=./cmoc-wrapper
compiler.cmoc.name=cmoc
postProcess=sed -e '/^;\t.stab/d' -e '/^\* /d'

Copy the cmoc-wrapper to the gcc-explorer folder and make it executable:
chmod +x cmoc-wrapper

make run LANG=C


Example study

1) Paste the below test example into the source window, and see
   -Os simply lays out the array in the code while
   -O1 puts the whole array on the stack - because it can.
2) Make the testFunction() static
   See how -O1 now is smarter and much shorter (!) than -Os
3) Move the "a" array definition out of main ()
   See how -O1 avoids the cycle-expensive tfr whereas
   -Os sticks to it. Sizes are similar.
4) Make also the "a" array static. Who's the champ now?

/* test example */

int testFunction(int* input, int length) {
  int sum = 0;
  for (int i = 0; i < length; ++i) {
    sum += input[i];
  }
  return sum;
}

int main (void)
{
	int a[] = {11,22,33,46,55};

	return testFunction(a, 5);
}

/* end test example */