re PR tree-optimization/84486 (code hoisting removes alignment assumption)

2018-03-05  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/84486
	* tree-ssa-pre.c (create_expression_by_pieces): Remove dead code.
	When inserting a __builtin_assume_aligned call set the LHS
	SSA name alignment info accordingly.

From-SVN: r258249

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index eeb3633..c523256 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-03-05  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/84486
+       * tree-ssa-pre.c (create_expression_by_pieces): Remove dead code.
+       When inserting a __builtin_assume_aligned call set the LHS
+       SSA name alignment info accordingly.
+
 2018-03-05  Wilco Dijkstra  <wdijkstr@arm.com>
 
        PR tree-optimization/84114

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index fa3daf4..8df15bf 100644 (file)
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -2749,11 +2749,7 @@ create_expression_by_pieces (basic_block block, pre_expr expr,
          unsigned int operand = 1;
          vn_reference_op_t currop = &ref->operands[0];
          tree sc = NULL_TREE;
-         tree fn;
-         if (TREE_CODE (currop->op0) == FUNCTION_DECL)
-           fn = currop->op0;
-         else
-           fn = find_or_generate_expression (block, currop->op0, stmts);
+         tree fn  = find_or_generate_expression (block, currop->op0, stmts);
          if (!fn)
            return NULL_TREE;
          if (currop->op1)
@@ -2771,14 +2767,27 @@ create_expression_by_pieces (basic_block block, pre_expr expr,
                return NULL_TREE;
              args.quick_push (arg);
            }
-         gcall *call
-           = gimple_build_call_vec ((TREE_CODE (fn) == FUNCTION_DECL
-                                     ? build_fold_addr_expr (fn) : fn), args);
+         gcall *call = gimple_build_call_vec (fn, args);
          gimple_call_set_with_bounds (call, currop->with_bounds);
          if (sc)
            gimple_call_set_chain (call, sc);
          tree forcedname = make_ssa_name (currop->type);
          gimple_call_set_lhs (call, forcedname);
+         /* There's no CCP pass after PRE which would re-compute alignment
+            information so make sure we re-materialize this here.  */
+         if (gimple_call_builtin_p (call, BUILT_IN_ASSUME_ALIGNED)
+             && args.length () - 2 <= 1
+             && tree_fits_uhwi_p (args[1])
+             && (args.length () != 3 || tree_fits_uhwi_p (args[2])))
+           {
+             unsigned HOST_WIDE_INT halign = tree_to_uhwi (args[1]);
+             unsigned HOST_WIDE_INT hmisalign
+               = args.length () == 3 ? tree_to_uhwi (args[2]) : 0;
+             if ((halign & (halign - 1)) == 0
+                 && (hmisalign & ~(halign - 1)) == 0)
+               set_ptr_info_alignment (get_ptr_info (forcedname),
+                                       halign, hmisalign);
+           }
          gimple_set_vuse (call, BB_LIVE_VOP_ON_EXIT (block));
          gimple_seq_add_stmt_without_update (&forced_stmts, call);
          folded = forcedname;