Steven Bosscher <stevenb....@gmail.com> writes: > And finally: expand. This should be just a change of IR format, from > GIMPLE to RTL. I have no idea why this pass always shows up in the top > 10 of slowest parts of GCC. Lowering passes on e.g. WHIRL, or GENERIC > lowering to GIMPLE, never show up in the compile time overviews.
expand unfortunately does more than just convert IR. It also does things like changing division by a constant into multiplication by a constant, and changing multiplication by a constant into a set of shifts and adds. It does various optimizations involving store flags (a = b == c;). When expanding function calls, it generates instructions to put arguments in the right place in registers and on the stack. Etc. Ian
