Ping? https://gcc.gnu.org/ml/gcc-patches/2016-08/msg00872.html
Thanks, Kugan On 11 August 2016 at 09:09, kugan <kugan.vivekanandara...@linaro.org> wrote: > Hi, > > > On 10/08/16 20:28, Richard Biener wrote: >> >> On Wed, Aug 10, 2016 at 10:57 AM, Jakub Jelinek <ja...@redhat.com> wrote: >>> >>> On Wed, Aug 10, 2016 at 08:51:32AM +1000, kugan wrote: >>>> >>>> I see it now. The problem is we are just looking at (-1) being in the >>>> ops >>>> list for passing changed to rewrite_expr_tree in the case of >>>> multiplication >>>> by negate. If we have combined (-1), as in the testcase, we will not >>>> have >>>> the (-1) and will pass changed=false to rewrite_expr_tree. >>>> >>>> We should set changed based on what happens in try_special_add_to_ops. >>>> Attached patch does this. Bootstrap and regression testing are ongoing. >>>> Is >>>> this OK for trunk if there is no regression. >>> >>> >>> I think the bug is elsewhere. In particular in >>> undistribute_ops_list/zero_one_operation/decrement_power. >>> All those look problematic in this regard, they change RHS of statements >>> to something that holds a different value, while keeping the LHS. >>> So, generally you should instead just add a new stmt next to the old one, >>> and adjust data structures (replace the old SSA_NAME in some ->op with >>> the new one). decrement_power might be a problem here, dunno if all the >>> builtins are const in all cases that DSE would kill the old one, >>> Richard, any preferences for that? reset flow sensitive info + reset >>> debug >>> stmt uses, or something different? Though, replacing the LHS with a new >>> anonymous SSA_NAME might be needed too, in case it is before SSA_NAME of >>> a >>> user var that doesn't yet have any debug stmts. >> >> >> I'd say replacing the LHS is the way to go, with calling the appropriate >> helper >> on the old stmt to generate a debug stmt for it / its uses (would need >> to look it >> up here). >> > > Here is an attempt to fix it. The problem arises when in > undistribute_ops_list, we linearize_expr_tree such that NEGATE_EXPR is added > (-1) MULT_EXPR (OP). Real problem starts when we handle this in > zero_one_operation. Unlike what was done earlier, we now change the stmt > (with propagate_op_to_signle use or by directly) such that the value > computed by stmt is no longer what it used to be. Because of this, what is > computed in undistribute_ops_list and rewrite_expr_tree are also changed. > > undistribute_ops_list already expects this but rewrite_expr_tree will not if > we dont pass the changed as an argument. > > The way I am fixing this now is, in linearize_expr_tree, I set ops_changed > to true if we change NEGATE_EXPR to (-1) MULT_EXPR (OP). Then when we call > zero_one_operation with ops_changed = true, I replace all the LHS in > zero_one_operation with the new SSA and replace all the uses. I also call > the rewrite_expr_tree with changed = false in this case. > > Does this make sense? Bootstrapped and regression tested for > x86_64-linux-gnu without any new regressions. > > Thanks, > Kugan > > > gcc/testsuite/ChangeLog: > > 2016-08-10 Kugan Vivekanandarajah <kug...@linaro.org> > > PR tree-optimization/72835 > * gcc.dg/tree-ssa/pr72835.c: New test. > > gcc/ChangeLog: > > 2016-08-10 Kugan Vivekanandarajah <kug...@linaro.org> > > PR tree-optimization/72835 > * tree-ssa-reassoc.c (zero_one_operation): Incase of NEGATE_EXPR > create and use > new SSA_NAME. > (try_special_add_to_ops): Return true if we changed the value in > operands. > (linearize_expr_tree): Return true if try_special_add_top_ops set > ops_changed to true. > (undistribute_ops_list): Likewise. > (reassociate_bb): Pass ops_changed returned by linearlize_expr_tree > to rewrite_expr_tree. > > > > whil cif we change the operands such that the > > /zero_one_operation
