On Tue, 14 Dec 2010 00:16:28 +0100 Wolfgang Denk wd@denx.de wrote:
Just two questions:
Q1: Are we sure that the observed behaviour is intentional, and not eventually unintended behaviour (well, a bug) in the new versions of GCC? In general newer releases are supposed to provide better optimization, but with GCC regressions seem to be more common?
I'm pretty sure it's intentional (though lacking an option to turn it off seems ill-advised). It should reduce code size normally -- it's just that NAND SPL is too small for the savings to overcome the fixed cost of the mechanism. The main U-Boot images do seem to have gotten a bit smaller with 4.5.
Going from 4.3 (doesn't do this) to 4.5 (does do this), I see SPL size increases of between 16 and 112 bytes. None of the boards in this patch went over 4096 bytes. Using -O2 instead of -Os, which disables this "optimization", with 4.5 results in even larger SPLs (with or without this patch).
Q2: What happens with older compilers, that don't need this? Is this change a No-Op for these?
With compilers that don't do this, the symbol references won't be generated, and no part of libgcc.a will be pulled in.
-Scott