Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard. 2018-09-25 Richard Biener <rguent...@suse.de> PR tree-optimization/87402 * tree-ssa-sccvn.c (SSA_VISITED): Remove unused function. (visit_phi): Re-instantiate handling of supposed to be VARYING but non-VARYING backedge value. * gcc.dg/torture/pr87402.c: New testcase. Index: gcc/tree-ssa-sccvn.c =================================================================== --- gcc/tree-ssa-sccvn.c (revision 264564) +++ gcc/tree-ssa-sccvn.c (working copy) @@ -464,15 +464,6 @@ SSA_VAL (tree x, bool *visited = NULL) return tem && tem->visited ? tem->valnum : x; } -/* Return whether X was visited. */ - -inline bool -SSA_VISITED (tree x) -{ - vn_ssa_aux_t tem = vn_ssa_aux_hash->find_with_hash (x, SSA_NAME_VERSION (x)); - return tem && tem->visited; -} - /* Return the SSA value of the VUSE x, supporting released VDEFs during elimination which will value-number the VDEF to the associated VUSE (but not substitute in the whole lattice). */ @@ -4196,7 +4187,10 @@ visit_phi (gimple *phi, bool *inserted, } } - /* If we value-number a virtual operand never value-number to the + /* If the value we want to use is flowing over the backedge and we + should take it as VARYING but it has a non-VARYING value drop to + VARYING. + If we value-number a virtual operand never value-number to the value from the backedge as that confuses the alias-walking code. See gcc.dg/torture/pr87176.c. If the value is the same on a non-backedge everything is OK though. */ @@ -4204,7 +4198,8 @@ visit_phi (gimple *phi, bool *inserted, && !seen_non_backedge && TREE_CODE (backedge_val) == SSA_NAME && sameval == backedge_val - && SSA_NAME_IS_VIRTUAL_OPERAND (backedge_val)) + && (SSA_NAME_IS_VIRTUAL_OPERAND (backedge_val) + || SSA_VAL (backedge_val) != backedge_val)) /* Note this just drops to VARYING without inserting the PHI into the hashes. */ result = PHI_RESULT (phi); Index: gcc/testsuite/gcc.dg/torture/pr87402.c =================================================================== --- gcc/testsuite/gcc.dg/torture/pr87402.c (nonexistent) +++ gcc/testsuite/gcc.dg/torture/pr87402.c (working copy) @@ -0,0 +1,33 @@ +/* { dg-do compile } */ + +void +xl (int co) +{ + int ar = 0; + + if (ar != 0) + { + int pp, ll = 0; + int *zx; + + if (co == 0) + { + } + else + { + zx = &pp; + + if (co < 0) + while (co < 1) + { +to: + while (ll < 1) + ++ll; + } + + *zx = (__INTPTR_TYPE__)&ar; + } + } + + goto to; +}