On Thu, Jul 12, 2012 at 2:24 PM, Steven Bosscher <stevenb....@gmail.com> wrote: > Hello, > > The global variable first_pass_instance exists to hack jump threading, > see tree-pass.h: > > /* Set to true if the pass is called the first time during compilation of the > current function. Note that using this information in the optimization > passes is considered not to be clean, and it should be avoided if possible. > This flag is currently used to prevent loops from being peeled repeatedly > in jump threading; it will be removed once we preserve loop structures > throughout the compilation -- we will be able to mark the affected loops > directly in jump threading, and avoid peeling them next time. */ > extern bool first_pass_instance; > > AFAIU, GCC now actually does preserve loops, so it should be possible > to remove this hack. > > But the recent changes in tree-ssa-reassoc.c introduced a new user of > first_pass_instance (apparently a fat comment discouraging its use is > not enough...). > > The attached patch fixes this by splitting pass_reassoc in an early > and a late pass. The pass names are reassoc1 and reassoc2 to avoid > changing a large number of test cases. Admittedly also not ideal, but > better than first_pass_instance. > > Richi, could you please have a look at jump threading, and see if > first_pass_instance can be remove? > > Bootstrapped&tested on x86_64-unknown-linux-gnu. OK for trunk?
This was proposed before and I did not like that, it makes -fdump-tree-reassoc non-functional (you have to use -fdump-tree-reassoc1 -fdump-tree-reassoc2). I much prefer an internal "hack" than such externally visible oddity. That said, add to struct pass a member "instance number" which a pass can check via current_pass. Richard. > Ciao! > Steven > > * tree-ssa-reassoc.c (linearize_expr_tree, undistribute_ops_list, > reassociate_bb, do_reassoc, execute_reassoc): Take extra EARLY_PASS > bool argument to distinguish between the early and late reassociation > pass. > (acceptable_pow_call): Do not look at first_pass_instance. > (execute_early_reassoc, execute_late_reassoc): New functions. > (pass_early_reassoc, pass_late_reassoc): New gimple_opt_pass structs. > (pass_reassoc): Removed. > * tree-pass.h (pass_reassoc): Removed. > (pass_early_reassoc, pass_late_reassoc): Declare. > * passes.c (init_optimization_passes): Schedule pass_early_reassoc and > pass_late_reassoc instead of pass_reassoc.
