Fix wrong-code issue in VN

The following fixes the wrong removed dead store discovered on the
PR108657 testcase when the reported DSE issue is not fixed.
The issue is we were using ssa_undefined_value_p on virtual operands
which returns a result based on the real definition of the definition
statement.  That doesn't make sense so this patch guards the calls
properly and makes sure nobody else does the same mistake.

	* tree-ssa.cc (ssa_undefined_value_p): Assert we are not
	called on virtual operands.
	* tree-ssa-sccvn.cc (vn_phi_lookup): Guard
	ssa_undefined_value_p calls.
	(vn_phi_insert): Likewise.
	(set_ssa_val_to): Likewise.
	(visit_phi): Avoid extra work with equivalences for
	virtual operand PHIs.

diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index 8ee77fd2b7877539649c0f760ef373d29c595cac..d5b081a309fe1ed93a3e8b36371bd2365a6979a5 100644 (file)
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -4824,7 +4824,8 @@ vn_phi_lookup (gimple *phi, bool backedges_varying_p)
       if (TREE_CODE (def) == SSA_NAME
          && (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK)))
        {
-         if (ssa_undefined_value_p (def, false))
+         if (!virtual_operand_p (def)
+             && ssa_undefined_value_p (def, false))
            def = VN_TOP;
          else
            def = SSA_VAL (def);
@@ -4877,7 +4878,8 @@ vn_phi_insert (gimple *phi, tree result, bool backedges_varying_p)
       if (TREE_CODE (def) == SSA_NAME
          && (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK)))
        {
-         if (ssa_undefined_value_p (def, false))
+         if (!virtual_operand_p (def)
+             && ssa_undefined_value_p (def, false))
            def = VN_TOP;
          else
            def = SSA_VAL (def);
@@ -5059,6 +5061,7 @@ set_ssa_val_to (tree from, tree to)
        }
       curr_invariant = is_gimple_min_invariant (currval);
       curr_undefined = (TREE_CODE (currval) == SSA_NAME
+                       && !virtual_operand_p (currval)
                        && ssa_undefined_value_p (currval, false));
       if (currval != VN_TOP
          && !curr_invariant
@@ -5081,6 +5084,7 @@ set_ssa_val_to (tree from, tree to)
       else if (currval != VN_TOP
               && !curr_undefined
               && TREE_CODE (to) == SSA_NAME
+              && !virtual_operand_p (to)
               && ssa_undefined_value_p (to, false))
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
@@ -5116,6 +5120,7 @@ set_and_exit:
          PR82320 for a testcase were we'd otherwise not terminate iteration.  */
       && !(curr_undefined
           && TREE_CODE (to) == SSA_NAME
+          && !virtual_operand_p (to)
           && ssa_undefined_value_p (to, false))
       /* ???  For addresses involving volatile objects or types operand_equal_p
          does not reliably detect ADDR_EXPRs as equal.  We know we are only
@@ -5880,7 +5885,14 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
            sameval = def;
            sameval_e = e;
          }
-       else if (!expressions_equal_p (def, sameval))
+       else if (expressions_equal_p (def, sameval))
+         sameval_e = NULL;
+       else if (virtual_operand_p (def))
+         {
+           sameval = NULL_TREE;
+           break;
+         }
+       else
          {
            /* We know we're arriving only with invariant addresses here,
               try harder comparing them.  We can do some caching here
@@ -5957,8 +5969,6 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
            sameval = NULL_TREE;
            break;
          }
-       else
-         sameval_e = NULL;
       }
 
   /* If the value we want to use is flowing over the backedge and we

diff --git a/gcc/tree-ssa.cc b/gcc/tree-ssa.cc
index 5126020d40ff87bbee721158711e956c9052897b..a5cad2d344e6d7d79961288b9bd1856aead35b0e 100644 (file)
--- a/gcc/tree-ssa.cc
+++ b/gcc/tree-ssa.cc
@@ -1320,6 +1320,8 @@ ssa_undefined_value_p (tree t, bool partial)
 {
   gimple *def_stmt;
 
+  gcc_checking_assert (!virtual_operand_p (t));
+
   if (ssa_defined_default_def_p (t))
     return false;