[PATCH v4 4/6] tree-object-size: Handle function parameters

[Siddhesh Poyarekar]

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):
        New function.
        (main): Call it.

Signed-off-by: Siddhesh Poyarekar <siddh...@gotplt.org>
---
 .../gcc.dg/builtin-dynamic-object-size-0.c    | 11 ++++
 gcc/tree-object-size.c                        | 50 ++++++++++++++++++-
 2 files changed, 60 insertions(+), 1 deletion(-)

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 ddedf6a49bd..ce0f4eb17f3 100644
--- a/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
+++ b/gcc/testsuite/gcc.dg/builtin-dynamic-object-size-0.c
@@ -46,6 +46,14 @@ 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);
+}
+
 unsigned nfails = 0;
 
 #define FAIL() ({ \
@@ -64,6 +72,9 @@ main (int argc, char **argv)
     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 ();
 
   if (nfails > 0)
     __builtin_abort ();
diff --git a/gcc/tree-object-size.c b/gcc/tree-object-size.c
index dd6c90efebf..bbc708f8ade 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"
@@ -1449,6 +1450,53 @@ 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);
+
+  /* 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; argpos != access->sizarg && arg;
+          arg = TREE_CHAIN (arg), ++argpos);
+
+      if (arg != NULL_TREE && 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);
+           }
+       }
+    }
+  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.  */
 
@@ -1606,7 +1654,7 @@ 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);
-- 
2.31.1