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Re: About the is_gimple_min_invariant predicate


> This is invalid gimple.

Right, but nevertheless is_gimple_val.

> Can you figure our why we don't gimplify this to 
>
> tmp_1 = MAX_EXPR <D.738_31, 0>;
> tmp_2 = (<unnamed-signed:32>)tmp_1;
> tmp_3 = tmp_2 + 1;
> &p_name_buffer[tmp3]

Because there is no code to do it.  If I add it:

Index: tree-ssa-pre.c
===================================================================
--- tree-ssa-pre.c      (revision 126300)
+++ tree-ssa-pre.c      (working copy)
@@ -3682,6 +3682,8 @@ eliminate (void)
                  && (TREE_CODE (*rhs_p) != SSA_NAME
                      || may_propagate_copy (*rhs_p, sprime)))
                {
+                 tree forced_stmts;
+
                  gcc_assert (sprime != *rhs_p);

                  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -3705,7 +3707,24 @@ eliminate (void)
                    sprime = fold_convert (TREE_TYPE (*rhs_p), sprime);

                  pre_stats.eliminations++;
+
+                /* Force the available computation to be a sequence of GIMPLE
+                    statements.
+                    We have to call unshare_expr because force_gimple_operand
+                    may modify the tree we pass to it.  */
+                 sprime = force_gimple_operand (unshare_expr (sprime),
+                                                &forced_stmts, false, NULL);
                  propagate_tree_value (rhs_p, sprime);
+
+                 if (forced_stmts)
+                   {
+                     tree_stmt_iterator tsi = tsi_start (forced_stmts);
+                     for (; !tsi_end_p (tsi); tsi_next (&tsi))
+                       mark_symbols_for_renaming (tsi_stmt (tsi));
+
+                     bsi_insert_before (&i, forced_stmts, BSI_SAME_STMT);
+                   }
+

it doesn't do anything since the expression is_gimple_val.

-- 
Eric Botcazou


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