[Bug tree-optimization/83128] Unable to optimize {m,c}alloc when strings builtin are used

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83128

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2017-11-23
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c        (revision 255093)
+++ gcc/tree-ssa-sccvn.c        (working copy)
@@ -1388,10 +1388,14 @@ fully_constant_vn_reference_p (vn_refere
       else if (base->opcode == MEM_REF
               && base[1].opcode == ADDR_EXPR
               && (TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == VAR_DECL
-                  || TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == CONST_DECL))
+                  || TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == CONST_DECL
+                  || TREE_CODE (TREE_OPERAND (base[1].op0, 0)) == STRING_CST))
        {
          decl = TREE_OPERAND (base[1].op0, 0);
-         ctor = ctor_for_folding (decl);
+         if (TREE_CODE (decl) == STRING_CST)
+           ctor = decl;
+         else
+           ctor = ctor_for_folding (decl);
        }
       if (ctor == NULL_TREE)
        return build_zero_cst (ref->type);
@@ -2331,7 +2335,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree
              rhs = TREE_OPERAND (tem, 0);
              rhs_offset += tree_to_uhwi (TREE_OPERAND (tem, 1));
            }
-         else if (DECL_P (tem))
+         else if (DECL_P (tem)
+                  || TREE_CODE (tem) == STRING_CST)
            rhs = build_fold_addr_expr (tem);
          else
            return (void *)-1;