XCore Exchange

robertxmos wrote:Hi Bambus
I would also recommend building with -Os in general.
The -O3 flag also turns on -mdual-issue which does not do a good job at present, hence will fill the slots with too many nops.

I have never heard this piece of advice. Which version of the tools does this apply to? I think with the 14.3 tools the -mdual-issue isn't enabled by default by -O3.

xcc1llvm test.xc -O3 -march=xs2a
xcc2clang test.c -O3 -march=xs2a -S -o -
and you will see ".issue_mode dual"

xcc1llvm test.xc -Os -march=xs2a
xcc2clang test.c -Os -march=xs2a -S -o -
and you will see ".issue_mode single"

It was discussed turning dual issue off for -O2 or even by default - but it remains on for both.