Integer multiplication problem

[mikebell]

I've just started experimenting with my new Parallella board, and had a play with the basic_math example in epiphany_examples/cpu

As a simple test to compare integer and floating point operations, I modified that test to do the basic math operations on integers instead of floats.

I then came across a weird problem where the result of the multiplication is wrong - I get 3 * 2 = 0! This only seems to happen when -O or higher is given to e-gcc. Looking at the assembler output nothing seems obviously wrong to my untrained eye.

The repro scenario goes away fairly easily when you start removing code from the example, but I've managed to cut it down a reasonable amount while preserving the bad behavior. Example project attached. If you edit build.sh to remove the -O then the test no longer fails.

Any clues as to what's going on here?