On Thu, 22 Dec 2022, Jakub Jelinek wrote: > Hi! > > The following place in value_replacement is after proving that > x == cst1 ? cst2 : x > phi result is only used in a comparison with constant which doesn't > care if it compares cst1 or cst2 and replaces it with x. > The testcase is miscompiled because we have after the replacement > incorrect range info for the phi result, we would need to > effectively union the phi result range with cst1 (oarg in the code) > because previously that constant might be missing in the range, but > newly it can appear (we've just verified that the single use stmt > of the phi result doesn't care about that value in particular). > > The following patch just resets the info, bootstrapped/regtested > on x86_64-linux and i686-linux, ok for trunk?
OK. > Aldy/Andrew, how would one instead union the SSA_NAME_RANGE_INFO > with some INTEGER_CST and store it back into SSA_NAME_RANGE_INFO > (including adjusting non-zero bits and the like)? There's no get_range_info on SSA_NAMEs (anymore?) but you can construct a value_range from the INTEGER_CST singleton and union that into the SSA_NAMEs range and then do set_range_info with the altered range I guess. Richard. > 2022-12-22 Jakub Jelinek <ja...@redhat.com> > > PR tree-optimization/108166 > * tree-ssa-phiopt.cc (value_replacement): For the maybe_equal_p > case turned into equal_p reset SSA_NAME_RANGE_INFO of phi result. > > * g++.dg/torture/pr108166.C: New test. > > --- gcc/tree-ssa-phiopt.cc.jj 2022-10-28 11:00:53.970243821 +0200 > +++ gcc/tree-ssa-phiopt.cc 2022-12-21 14:27:58.118326548 +0100 > @@ -1491,6 +1491,12 @@ value_replacement (basic_block cond_bb, > default: > break; > } > + if (equal_p) > + /* After the optimization PHI result can have value > + which it couldn't have previously. > + We could instead of resetting it union the range > + info with oarg. */ > + reset_flow_sensitive_info (gimple_phi_result (phi)); > if (equal_p && MAY_HAVE_DEBUG_BIND_STMTS) > { > imm_use_iterator imm_iter; > --- gcc/testsuite/g++.dg/torture/pr108166.C.jj 2022-12-21 > 14:31:02.638661322 +0100 > +++ gcc/testsuite/g++.dg/torture/pr108166.C 2022-12-21 14:30:45.441909725 > +0100 > @@ -0,0 +1,26 @@ > +// PR tree-optimization/108166 > +// { dg-do run } > + > +bool a, b; > +int d, c; > + > +const int & > +foo (const int &f, const int &g) > +{ > + return !f ? f : g; > +} > + > +__attribute__((noipa)) void > +bar (int) > +{ > +} > + > +int > +main () > +{ > + c = foo (b, 0) > ((b ? d : b) ?: 8); > + a = b ? d : b; > + bar (a); > + if (a != 0) > + __builtin_abort (); > +} > > Jakub > > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)