[fortran,committed] Don't check for NULL pointers before calling free()

[fortran,committed] Don't check for NULL pointers before calling free()

[FX]

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The attached patch changes the gfc_call_free() function to simply call __builtin_free() without first checking if the pointer is NULL, because free(NULL) is a nop. This simplifies code, but could lead to pessimization in cases where the pointer is likely to be NULL, and the test would have saved the function call. After auditing all the gfc_call_free() callers in the front-end, I come to the conclusion that there are no such cases (in fact, in most cases, the front-end knows for sure that the pointer is non-NULL, because it was just allocated some lines earlier).

Committed as rev. 227336 after bootstrap and regtesting on x86_64-apple-darwin15.

FX



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2015-08-31  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>

	PR fortran/54833
	* trans.c (gfc_call_free): Don't check if pointer is NULL.
	* trans.h (gfc_call_free): Adjust comment.


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Index: gcc/fortran/trans.c
===================================================================
--- gcc/fortran/trans.c	(revision 227316)
+++ gcc/fortran/trans.c	(working copy)
@@ -850,23 +850,14 @@ gfc_allocate_allocatable (stmtblock_t * 
 }
 
 
-/* Free a given variable, if it's not NULL.  */
+/* Free a given variable.  */
 
 tree
 gfc_call_free (tree var)
 {
-  tree cond, call;
-
-  /* Only evaluate the variable once.  */
-  var = save_expr (fold_convert (pvoid_type_node, var));
-
-  cond = fold_build2_loc (input_location, NE_EXPR, boolean_type_node, var,
-			  build_int_cst (pvoid_type_node, 0));
-  call = build_call_expr_loc (input_location,
+  return build_call_expr_loc (input_location,
 			      builtin_decl_explicit (BUILT_IN_FREE),
-			      1, var);
-  return fold_build3_loc (input_location, COND_EXPR, void_type_node,
-			  cond, call, build_empty_stmt (input_location));
+			      1, fold_convert (pvoid_type_node, var));
 }
 
 
Index: gcc/fortran/trans.h
===================================================================
--- gcc/fortran/trans.h	(revision 227316)
+++ gcc/fortran/trans.h	(working copy)
@@ -642,7 +642,7 @@ void gfc_trans_runtime_check (bool, bool
 void gfc_trans_same_strlen_check (const char*, locus*, tree, tree,
 				  stmtblock_t*);
 
-/* Generate a call to free() after checking that its arg is non-NULL.  */
+/* Generate a call to free().  */
 tree gfc_call_free (tree);
 
 /* Allocate memory after performing a few checks.  */