On Wed, Dec 12, 2012 at 12:27 PM, Yuri Rumyantsev <ysrum...@gmail.com> wrote: > Hi All, > > 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). Richard. > ChangeLog: > > 2012-12-12 Yuri Rumyantsev <ysrum...@gmail.com> > > * config/i386/i386.c (ix86_legitimate_combined_insn) : Avoid combining > of load and if_then_else instructions.
