Hi All, Forgot to attch the patch.
2012/9/18 Yuri Rumyantsev <ysrum...@gmail.com>: > Hi All, > > This patch aims to fix all stability issues related to using the first > scheduler in gcc > for x86 target (there several reported issues related to this problem). > > Main idea of this activity is mostly to provide user a possibility to > safely turn on first scheduler for his codes. In some cases this could > positively affect performance, especially for in-order Atom. > > Below is short description of proposed changes. > > Main idea of this patch is to restrict code motion of instructions > having likely spilled HW registers as their operands - in general > all these instructions are unloading of incoming function argument > in the function entry and passing of outgoing function arguments. > This is essential for correct scheduling since live range of such insns > is not defined before register allocation phase. > This done through 2 hooks: > > 1. ix86_adjust_priority which sets up the priority of moves from > likely spilled HW registers to maximum that allows us to schedule > such insns as soon as possible, i.e. all moves correspondent to > incoming function arguments will be scheduled at the top of > function entry and moves correspondent to function return > value will be scheduled immediately after call. > 2. ix86_dependencies_evaluation_hook which insert additional > dependencies for outgoing function arguments passed in likely > spilled HW registers to avoid their code motion. This is done > through the following steps: > - scan the current schedule region to find all call instructions in > reverse order; > - find out the first argument that passed in likely spilled HW > register. Starting from it insert output dependency between it and > possible previous argument (it does not matter if it passed in likely > spilled register or not). This is done in add_parameter_dependencies; > after it all arguments starting from the first one that is passed in > likely spilled register are pairwise connected through output > dependency. > - add dependencies to the first function argument on > the rest of instructions in the current block (until next call) to avoid > intra block code motion. > - to avoid possible interblock code motion we also check if the first > argument has dependee in another blocks and if so insert dependency to > the last non-jump set instruction. > > This patch was deeply tested on Atom (eembc_2_0, spec2000 in base/peak mode) > and Big Core (spec2006 in base/peak mode). > Also gcc full bootstrapping with turned on 1st scheduler by default was done. > > Tested for i386 and x86-64, ok for trunk? > > ChangeLog: > > 2012-09-18 Yuri Rumyantsev <ysrum...@gmail.com> > > * config/i386/i386.c (ix86_dep_by_shift_count_body) : Add > check on reload_completed since it can be invoked before > register allocation phase in 1st scheduler. > (ia32_multipass_dfa_lookahead) : Do not use dfa_lookahead for 1st > Scheduler to save compile time. > (ix86_sched_reorder) : Do not perform ready list reordering for 1st > Scheduler to save compile time. > (insn_is_function_arg) : New function. Returns true if lhs of insn is > HW function argument register. > (add_parameter_dependencies) : New function. Add output dependencies > for chain of function adjacent arguments if only there is a move to > likely spilled HW registers. Return first argument if at least one > dependence was added or NULL otherwise. > (avoid_func_arg_motion) : New function. Add output or anti dependency > from insn to first_arg to restrict code motion. > (add_dependee_for_func_arg) : New function. Avoid cross block motion > of > function argument through adding dependency from the first non-jump > insn in bb. > (ix86_dependencies_evaluation_hook) : New function. Hook for > schedule1: > avoid motion of function arguments passed in passed in likely spilled > HW registers. > (ix86_adjust_priority) : New function. Hook for schedule1: set > priority > of moves from likely spilled HW registers to maximum to schedule them > as soon as possible. > (ix86_sched_init_global): Do not perform multipass scheduling for 1st > Scheduler to save compile time.
i386-fschedule-insn_for_x86.diff
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