[Bug tree-optimization/102983] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102983 Andrew Macleod changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #4 from Andrew Macleod --- Rather than trying to fix this after the fact in the VRP folder when something is simplified, I fixed it directly inside ranger when it is processing gcond statements. Ranger will now update the cache following any range_of_stmt calls on a gcond so we will always be up to date. This way non-vrp clients will also get the same updates.
[Bug tree-optimization/102983] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102983 --- Comment #3 from CVS Commits --- The master branch has been updated by Andrew Macleod : https://gcc.gnu.org/g:cb596fd43667f92c4cb037a4ee8b2061c393ba60 commit r12-4788-gcb596fd43667f92c4cb037a4ee8b2061c393ba60 Author: Andrew MacLeod Date: Thu Oct 28 13:31:17 2021 -0400 Perform on-entry propagation after range_of_stmt on a gcond. Propagation is automatically done by the temporal cache when defs are out of date from the names on the RHS, but a gcond has no LHS, and any updates on the RHS are never propagated. Always propagate them. gcc/ PR tree-optimization/102983 * gimple-range-cache.h (propagate_updated_value): Make public. * gimple-range.cc (gimple_ranger::range_of_stmt): Propagate exports when processing gcond stmts. gcc/testsuite/ * gcc.dg/pr102983.c: New.
[Bug tree-optimization/102983] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102983 --- Comment #2 from Andrew Macleod --- This is a bit more interesting. The IL starts the pass as : if (c_3 < b_4) goto ; [INV] else goto ; [INV] : if (c_3 != 0) goto ; [INV] else goto ; [INV] <...> : # c_3 = PHI <0(2), c_2(10)> # b_4 = PHI <0(2), b_16(10)> if (b_4 <= 0) goto ; [INV] else goto ; [INV] so the initial condition is "if (c_3 < b_4)" the initial attempt to calculate c_3 = PHI flows along and uses a value of b_4 determined by loop analysis of [0,1]. (we haven't gotten to propagating b_4 along the back edges yet) so it ends up deciding c_3 has a range of [-INF, 1] We then plod along, and eventually handle b_4, and propagate that b_4 is [0,0[ on the edge 11->3. There is no direct dependency between c_3 and b_4, so there are no values going stale due to this updated value. Meanwhile, we eventually visit the if (c_3 < b_4) stmt, and b_4 is known to be 0, so the simplifier changes this to if (c_3 < 0). Ranger however, doesnt know this was simplified, and at the moment doesn't think it needs to recalculate any outgoing ranges and update on-entry cache values in successor blocks. It dDoesn't realize there is a reason to recalculate it. Whenever we successfully fold or simplify a conditional, we probably need to check if any values should then be propagated. I believe that it will happen automatically for anything that is defined by the statement due to the nature of the temporal cache. Statements like GIMPLE_COND which have no LHS have no triggers.
[Bug tree-optimization/102983] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102983 Richard Biener changed: What|Removed |Added Priority|P3 |P1
[Bug tree-optimization/102983] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102983 Andrew Pinski changed: What|Removed |Added Status|UNCONFIRMED |NEW Keywords||missed-optimization Last reconfirmed||2021-10-28 Ever confirmed|0 |1 Target Milestone|--- |12.0 --- Comment #1 from Andrew Pinski --- Hmm: : if (c_3 < 0) goto ; [INV] else goto ; [INV] : if (c_3 != 0) goto ; [INV] else goto ; [INV] === BB 5 Imports: c_3 b_4 Exports: c_3 b_4 c_3 int [-INF, 1] b_4 int [0, 0] : if (c_3 < 0) goto ; [INV] else goto ; [INV] 5->6 (T) c_3 : int [-INF, -1] 5->6 (T) b_4 : int [0, 0] 5->9 (F) c_3 : int [0, 1] 5->9 (F) b_4 : int [0, 0] === BB 6 Imports: c_3 Exports: c_3 c_3 int [-INF, 0] b_4 int [0, 0] : if (c_3 != 0) goto ; [INV] else goto ; [INV] 6->7 (T) c_3 : int [-INF, -1] 6->8 (F) c_3 : int [0, 0] H.
