On Wed, Dec 12, 2012 at 12:44 PM, Richard Biener <richard.guent...@gmail.com> wrote:
>> This fix is aimed to remove performance degradation introduced by new >> LRA phase that in fact is combining problem. Gcc combiner does >> propagation of memory load to if-then-else gimple that was splitted >> back by old reload phase. LRA does not perform such splitting. To >> avoid performance slowdown on important benchmark (this is true for >> all x86 targets) we decided to enhance 'ix86_legitimate_combined_insn' >> with a check on such propagation and consider such conditional >> instruction with memory operand as illegal one from performance point >> of view. >> >> The fix was bootstrapped and regtested for x86-64. >> Is it OK for 4.8 and mainline? > > Isn't it a win for -Os though? Thus, optimize_insn_for_size ()? It can > also increase register pressure, no? So eventually this splitting should > be done post-reload only. Not sure what appropriate machinery there is, > besides from mdreorg (or split itself). So, you are proposing to use peephole2 with (match_scratch) conditional temporary? Uros.
