[PATCH v6 2/4] tree-object-size: Handle function parameters

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

Handle hints provided by __attribute__ ((access (...))) to compute
dynamic sizes for objects.

gcc/ChangeLog:

	* tree-object-size.c: Include tree-dfa.h.
	(parm_object_size): New function.
	(collect_object_sizes_for): Call it.

gcc/testsuite/ChangeLog:

	* gcc.dg/builtin-dynamic-object-size-0.c (test_parmsz_simple,
	test_parmsz_scaled, test_parmsz_unknown): New functions.
	(main): Call them.  Add new arguments argc and argv.

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
---
 .../gcc.dg/builtin-dynamic-object-size-0.c    | 35 +++++++++++-
 gcc/tree-object-size.c                        | 54 ++++++++++++++++++-
 2 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
index b1013e19fd0..c89e2268943 100644
--- a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
@@ -34,6 +34,30 @@ test_deploop (size_t sz, size_t cond)
   return __builtin_dynamic_object_size (bin, 0);
 }
 
+size_t
+__attribute__ ((access (__read_write__, 1, 2)))
+__attribute__ ((noinline))
+test_parmsz_simple (void *obj, size_t sz)
+{
+  return __builtin_dynamic_object_size (obj, 0);
+}
+
+size_t
+__attribute__ ((access (__read_write__, 1, 2)))
+__attribute__ ((noinline))
+test_parmsz_scaled (int *obj, size_t sz)
+{
+  return __builtin_dynamic_object_size (obj, 0);
+}
+
+size_t
+__attribute__ ((access (__read_write__, 1, 3)))
+__attribute__ ((noinline))
+test_parmsz_unknown (void *obj, void *unknown, size_t sz, int cond)
+{
+  return __builtin_dynamic_object_size (cond ? obj : unknown, 0);
+}
+
 unsigned nfails = 0;
 
 #define FAIL() ({ \
@@ -42,7 +66,7 @@ unsigned nfails = 0;
 })
 
 int
-main ()
+main (int argc, char **argv)
 {
   if (test_builtin_malloc_condphi (1) != 32)
     FAIL ();
@@ -50,6 +74,15 @@ main ()
     FAIL ();
   if (test_deploop (128, 129) != 32)
     FAIL ();
+  if (test_parmsz_simple (argv[0], __builtin_strlen (argv[0]) + 1)
+      != __builtin_strlen (argv[0]) + 1)
+    FAIL ();
+  int arr[42];
+  if (test_parmsz_scaled (arr, 42) != sizeof (arr))
+    FAIL ();
+  if (test_parmsz_unknown (argv[0], argv[0], __builtin_strlen (argv[0]) + 1, 0)
+      != -1)
+    FAIL ();
 
   if (nfails > 0)
     __builtin_abort ();
diff --git a/gcc/tree-object-size.c b/gcc/tree-object-size.c
index 775792b4419..47e1c27bfd3 100644
--- a/gcc/tree-object-size.c
+++ b/gcc/tree-object-size.c
@@ -32,6 +32,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-fold.h"
 #include "gimple-iterator.h"
 #include "tree-cfg.h"
+#include "tree-dfa.h"
 #include "stringpool.h"
 #include "attribs.h"
 #include "builtins.h"
@@ -1443,6 +1444,57 @@ cond_expr_object_size (struct object_size_info *osi, tree var, gimple *stmt)
   return reexamine;
 }
 
+/* Find size of an object passed as a parameter to the function.  */
+
+static void
+parm_object_size (struct object_size_info *osi, tree var)
+{
+  int object_size_type = osi->object_size_type;
+  tree parm = SSA_NAME_VAR (var);
+
+  if (!(object_size_type & OST_DYNAMIC) || !POINTER_TYPE_P (TREE_TYPE (parm)))
+    {
+      expr_object_size (osi, var, parm);
+      return;
+    }
+
+  /* Look for access attribute.  */
+  rdwr_map rdwr_idx;
+
+  tree fndecl = cfun->decl;
+  const attr_access *access = get_parm_access (rdwr_idx, parm, fndecl);
+  tree typesize = TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (parm)));
+  tree sz = NULL_TREE;
+
+  if (access && access->sizarg != UINT_MAX)
+    {
+      tree fnargs = DECL_ARGUMENTS (fndecl);
+      tree arg = NULL_TREE;
+      unsigned argpos = 0;
+
+      /* Walk through the parameters to pick the size parameter and safely
+	 scale it by the type size.  */
+      for (arg = fnargs; arg; arg = TREE_CHAIN (arg), ++argpos)
+	{
+	  if (argpos == access->sizarg && INTEGRAL_TYPE_P (TREE_TYPE (arg)))
+	    {
+	      sz = get_or_create_ssa_default_def (cfun, arg);
+	      if (sz != NULL_TREE)
+		{
+		  sz = fold_convert (sizetype, sz);
+		  if (typesize)
+		    sz = size_binop (MULT_EXPR, sz, typesize);
+		}
+	      break;
+	    }
+	}
+    }
+  if (!sz)
+    sz = size_unknown (object_size_type);
+
+  object_sizes_set (osi, SSA_NAME_VERSION (var), sz, sz);
+}
+
 /* Compute an object size expression for VAR, which is the result of a PHI
    node.  */
 
@@ -1620,7 +1672,7 @@ collect_object_sizes_for (struct object_size_info *osi, tree var)
     case GIMPLE_NOP:
       if (SSA_NAME_VAR (var)
 	  && TREE_CODE (SSA_NAME_VAR (var)) == PARM_DECL)
-	expr_object_size (osi, var, SSA_NAME_VAR (var));
+	parm_object_size (osi, var);
       else
 	/* Uninitialized SSA names point nowhere.  */
 	unknown_object_size (osi, var);
-- 
2.33.1