On 26/07/12 11:27, Andrew Pinski wrote: > On Thu, Jul 26, 2012 at 3:20 AM, Bin Cheng <bin.ch...@arm.com> wrote: >> Hi, >> This patch removes the duplicate check on BRANCH_COST in fold_truth_andor. >> The BRANCH_COST condition removed is a duplicate of the default definition >> of LOGICAL_OP_NON_SHORT_CIRCUIT. >> All current targets (mips and rs6000) that provide non-default definitions >> of LOGICAL_OP_SHORT_CIRCUIT set it to 0, so this patch is therefore just a >> code cleanup and does not change behaviour in the compiler. >> >> I built mipsel-elf cross compiler and compared newlib/libstdc++ compiled by >> the patched/original compilers. >> >> Is it OK? > > Just some history here on this. The BRANCH COST check was there > before LOGICAL_OP_NON_SHORT_CIRCUIT was added. I will be submitting a > patch which changes the MIPS definition soon but it will not be based > on the branch cost but rather than another option. So in the end it > might not be redundant as it is currently. > > Thanks, > Andrew >
You can always factor BRANCH_COST into LOGICAL_OP_NON_SHORT_CIRCUIT (as the default currently does), so there's no loss of functionality from removing this currently redundant check. However, the current definition is broken in that it makes it impossible to force the compiler to use this optimization when the branch cost is low. R.
