Re: [PATCH, i386, Pointer Bounds Checker 32/x] Pointer Bounds Checker hooks for i386 target

[Ilya Enkovich <enkovich dot gnu at gmail dot com>]

On 23 Sep 09:51, Richard Biener wrote:
> On Mon, 22 Sep 2014, Uros Bizjak wrote:
> 
> > On Mon, Sep 22, 2014 at 5:30 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> > > On 19 Sep 18:21, Uros Bizjak wrote:
> > >> On Fri, Sep 19, 2014 at 2:53 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> > > +static int
> > > +ix86_initialize_bounds (tree var, tree lb, tree ub, tree *stmts)
> > > +{
> > > +  tree size_ptr = build_pointer_type (size_type_node);
> > > +  tree lhs, modify, var_p;
> > > +
> > > +  ub = build1 (BIT_NOT_EXPR, size_type_node, ub);
> > > +  var_p = build1 (CONVERT_EXPR, size_ptr,
> > > +                 build_fold_addr_expr (var));
> 
> Please use fold_convert (size_ptr, build_fold_addr_expr (var)).
> 
> Is 'var' always accessed via a size_t effective type?  Watch out
> for TBAA issues if not.  (if it is, why is 'var' not of type
> size_t or size_t[]?)

var has pointer bounds type.  I have to initialize it by parts and thus access it as a couple of integers having size of a pointer (I use integer instead of pointer because non poiner arithmetic is used).  Size type is not the best for this purpose and therefore I replace it with pointer_sized_int_node.

So I have accesses of var's parts as integers and accesses of whole var as bounds.  Should I expect some problems from TBAA here?  How can I avoid problems with TBAA if any exists?

> 
> > > +  lhs = build1 (INDIRECT_REF, size_type_node, var_p);
> > > +  modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, lb);
> > > +  append_to_statement_list (modify, stmts);
> > > +
> > > +  lhs = build1 (INDIRECT_REF, size_type_node,
> > > +               build2 (POINTER_PLUS_EXPR, size_ptr, var_p,
> > > +                       TYPE_SIZE_UNIT (size_type_node)));
> > > +  modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, ub);
> > > +  append_to_statement_list (modify, stmts);
> 
> This was used from inside the gimplifier?  Thus this is why you
> build GENERIC here and not GIMPLE?
> 
> Didn't spot any other "tree" stuff.
> 
> Richard.
> 

I build GENERIC to pass it to cgraph_build_static_cdtor.  Below is a new version.

Thanks,
Ilya
--
2014-09-23  Ilya Enkovich  <ilya.enkovich@intel.com>

	* config/i386/i386.c: Include tree-iterator.h.
	(ix86_function_value_bounds): New.
	(ix86_builtin_mpx_function): New.
	(ix86_get_arg_address_for_bt): New.
	(ix86_load_bounds): New.
	(ix86_store_bounds): New.
	(ix86_load_returned_bounds): New.
	(ix86_store_returned_bounds): New.
	(ix86_mpx_bound_mode): New.
	(ix86_make_bounds_constant): New.
	(ix86_initialize_bounds):
	(TARGET_LOAD_BOUNDS_FOR_ARG): New.
	(TARGET_STORE_BOUNDS_FOR_ARG): New.
	(TARGET_LOAD_RETURNED_BOUNDS): New.
	(TARGET_STORE_RETURNED_BOUNDS): New.
	(TARGET_CHKP_BOUND_MODE): New.
	(TARGET_BUILTIN_CHKP_FUNCTION): New.
	(TARGET_CHKP_FUNCTION_VALUE_BOUNDS): New.
	(TARGET_CHKP_MAKE_BOUNDS_CONSTANT): New.
	(TARGET_CHKP_INITIALIZE_BOUNDS): New.


diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index d493983..64bf5b4 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -85,6 +85,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-vectorizer.h"
 #include "shrink-wrap.h"
 #include "builtins.h"
+#include "tree-iterator.h"
 #include "tree-chkp.h"
 #include "rtl-chkp.h"
 
@@ -8001,6 +8002,51 @@ ix86_function_value (const_tree valtype, const_tree fntype_or_decl, bool)
   return ix86_function_value_1 (valtype, fntype_or_decl, orig_mode, mode);
 }
 
+/*  Return an RTX representing a place where a function returns
+    or recieves pointer bounds or NULL if no bounds are returned.
+
+    VALTYPE is a data type of a value returned by the function.
+
+    FN_DECL_OR_TYPE is a tree node representing FUNCTION_DECL
+    or FUNCTION_TYPE of the function.
+
+    If OUTGOING is false, return a place in which the caller will
+    see the return value.  Otherwise, return a place where a
+    function returns a value.  */
+
+static rtx
+ix86_function_value_bounds (const_tree valtype,
+			    const_tree fntype_or_decl ATTRIBUTE_UNUSED,
+			    bool outgoing ATTRIBUTE_UNUSED)
+{
+  rtx res = NULL_RTX;
+
+  if (BOUNDED_TYPE_P (valtype))
+    res = gen_rtx_REG (BNDmode, FIRST_BND_REG);
+  else if (chkp_type_has_pointer (valtype))
+    {
+      bitmap slots = chkp_find_bound_slots (valtype);
+      rtx bounds[2];
+      bitmap_iterator bi;
+      unsigned i, bnd_no = 0;
+
+      EXECUTE_IF_SET_IN_BITMAP (slots, 0, i, bi)
+	{
+	  rtx reg = gen_rtx_REG (BNDmode, FIRST_BND_REG + bnd_no);
+	  rtx offs = GEN_INT (i * POINTER_SIZE / BITS_PER_UNIT);
+	  gcc_assert (bnd_no < 2);
+	  bounds[bnd_no++] = gen_rtx_EXPR_LIST (VOIDmode, reg, offs);
+	}
+
+      res = gen_rtx_PARALLEL (VOIDmode, gen_rtvec_v (bnd_no, bounds));
+      BITMAP_FREE (slots);
+    }
+  else
+    res = NULL_RTX;
+
+  return res;
+}
+
 /* Pointer function arguments and return values are promoted to
    word_mode.  */
 
@@ -36754,6 +36800,193 @@ static tree ix86_get_builtin (enum ix86_builtins code)
     return NULL_TREE;
 }
 
+/* Return function decl for target specific builtin
+   for given MPX builtin passed i FCODE.  */
+static tree
+ix86_builtin_mpx_function (unsigned fcode)
+{
+  switch (fcode)
+    {
+    case BUILT_IN_CHKP_BNDMK:
+      return ix86_builtins[IX86_BUILTIN_BNDMK];
+
+    case BUILT_IN_CHKP_BNDSTX:
+      return ix86_builtins[IX86_BUILTIN_BNDSTX];
+
+    case BUILT_IN_CHKP_BNDLDX:
+      return ix86_builtins[IX86_BUILTIN_BNDLDX];
+
+    case BUILT_IN_CHKP_BNDCL:
+      return ix86_builtins[IX86_BUILTIN_BNDCL];
+
+    case BUILT_IN_CHKP_BNDCU:
+      return ix86_builtins[IX86_BUILTIN_BNDCU];
+
+    case BUILT_IN_CHKP_BNDRET:
+      return ix86_builtins[IX86_BUILTIN_BNDRET];
+
+    case BUILT_IN_CHKP_INTERSECT:
+      return ix86_builtins[IX86_BUILTIN_BNDINT];
+
+    case BUILT_IN_CHKP_NARROW:
+      return ix86_builtins[IX86_BUILTIN_BNDNARROW];
+
+    case BUILT_IN_CHKP_SIZEOF:
+      return ix86_builtins[IX86_BUILTIN_SIZEOF];
+
+    case BUILT_IN_CHKP_EXTRACT_LOWER:
+      return ix86_builtins[IX86_BUILTIN_BNDLOWER];
+
+    case BUILT_IN_CHKP_EXTRACT_UPPER:
+      return ix86_builtins[IX86_BUILTIN_BNDUPPER];
+
+    default:
+      return NULL_TREE;
+    }
+
+  gcc_unreachable ();
+}
+
+/* Helper function for ix86_load_bounds and ix86_store_bounds.
+
+   Return an address to be used to load/store bounds for pointer
+   passed in SLOT.
+
+   SLOT_NO is an integer constant holding number of a target
+   dependent special slot to be used in case SLOT is not a memory.
+
+   SPECIAL_BASE is a pointer to be used as a base of fake address
+   to access special slots in Bounds Table.  SPECIAL_BASE[-1],
+   SPECIAL_BASE[-2] etc. will be used as fake pointer locations.  */
+
+static rtx
+ix86_get_arg_address_for_bt (rtx slot, rtx slot_no, rtx special_base)
+{
+  rtx addr = NULL;
+
+  /* NULL slot means we pass bounds for pointer not passed to the
+     function at all.  Register slot means we pass pointer in a
+     register.  In both these cases bounds are passed via Bounds
+     Table.  Since we do not have actual pointer stored in memory,
+     we have to use fake addresses to access Bounds Table.  We
+     start with (special_base - sizeof (void*)) and decrease this
+     address by pointer size to get addresses for other slots.  */
+  if (!slot || REG_P (slot))
+    {
+      gcc_assert (CONST_INT_P (slot_no));
+      addr = plus_constant (Pmode, special_base,
+			    -(INTVAL (slot_no) + 1) * GET_MODE_SIZE (Pmode));
+    }
+  /* If pointer is passed in a memory then its address is used to
+     access Bounds Table.  */
+  else if (MEM_P (slot))
+    {
+      addr = XEXP (slot, 0);
+      if (!register_operand (addr, Pmode))
+	addr = copy_addr_to_reg (addr);
+    }
+  else
+    gcc_unreachable ();
+
+  return addr;
+}
+
+/* Expand pass uses this hook to load bounds for function parameter
+   PTR passed in SLOT in case its bounds are not passed in a register.
+
+   If SLOT is a memory, then bounds are loaded as for regular pointer
+   loaded from memory.  PTR may be NULL in case SLOT is a memory.
+   In such case value of PTR (if required) may be loaded from SLOT.
+
+   If SLOT is NULL or a register then SLOT_NO is an integer constant
+   holding number of the target dependent special slot which should be
+   used to obtain bounds.
+
+   Return loaded bounds.  */
+
+static rtx
+ix86_load_bounds (rtx slot, rtx ptr, rtx slot_no)
+{
+  rtx reg = gen_reg_rtx (BNDmode);
+  rtx addr;
+
+  /* Get address to be used to access Bounds Table.  Special slots start
+     at the location of return address of the current function.  */
+  addr = ix86_get_arg_address_for_bt (slot, slot_no, arg_pointer_rtx);
+
+  /* Load pointer value from a memory if we don't have it.  */
+  if (!ptr)
+    {
+      gcc_assert (MEM_P (slot));
+      ptr = copy_addr_to_reg (slot);
+    }
+
+  emit_insn (BNDmode == BND64mode
+	     ? gen_bnd64_ldx (reg, addr, ptr)
+	     : gen_bnd32_ldx (reg, addr, ptr));
+
+  return reg;
+}
+
+/* Expand pass uses this hook to store BOUNDS for call argument PTR
+   passed in SLOT in case BOUNDS are not passed in a register.
+
+   If SLOT is a memory, then BOUNDS are stored as for regular pointer
+   stored in memory.  PTR may be NULL in case SLOT is a memory.
+   In such case value of PTR (if required) may be loaded from SLOT.
+
+   If SLOT is NULL or a register then SLOT_NO is an integer constant
+   holding number of the target dependent special slot which should be
+   used to store BOUNDS.  */
+
+static void
+ix86_store_bounds (rtx ptr, rtx slot, rtx bounds, rtx slot_no)
+{
+  rtx addr;
+
+  /* Get address to be used to access Bounds Table.  Special slots start
+     at the location of return address of a called function.  */
+  addr = ix86_get_arg_address_for_bt (slot, slot_no, stack_pointer_rtx);
+
+  /* Load pointer value from a memory if we don't have it.  */
+  if (!ptr)
+    {
+      gcc_assert (MEM_P (slot));
+      ptr = copy_addr_to_reg (slot);
+    }
+
+  gcc_assert (POINTER_BOUNDS_MODE_P (GET_MODE (bounds)));
+  if (!register_operand (bounds, BNDmode))
+    bounds = copy_to_mode_reg (BNDmode, bounds);
+
+  emit_insn (BNDmode == BND64mode
+	     ? gen_bnd64_stx (addr, ptr, bounds)
+	     : gen_bnd32_stx (addr, ptr, bounds));
+}
+
+/* Load and return bounds returned by function in SLOT.  */
+
+static rtx
+ix86_load_returned_bounds (rtx slot)
+{
+  rtx res;
+
+  gcc_assert (REG_P (slot));
+  res = gen_reg_rtx (BNDmode);
+  emit_move_insn (res, slot);
+
+  return res;
+}
+
+/* Store BOUNDS returned by function into SLOT.  */
+
+static void
+ix86_store_returned_bounds (rtx slot, rtx bounds)
+{
+  gcc_assert (REG_P (slot));
+  emit_move_insn (slot, bounds);
+}
+
 /* Returns a function decl for a vectorized version of the builtin function
    with builtin function code FN and the result vector type TYPE, or NULL_TREE
    if it is not available.  */
@@ -47480,6 +47713,73 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree *clear, tree *update)
 		    atomic_feraiseexcept_call);
 }
 
+/* Return mode to be used for bounds or VOIDmode
+   if bounds are not supported.  */
+
+static enum machine_mode
+ix86_mpx_bound_mode ()
+{
+  /* Do not support pointer checker if MPX
+     is not enabled.  */
+  if (!TARGET_MPX)
+    {
+      if (flag_check_pointer_bounds)
+	warning (0, "Pointer Checker requires MPX support on this target."
+		 " Use -mmpx options to enable MPX.");
+      return VOIDmode;
+    }
+
+  return BNDmode;
+}
+
+/*  Return constant used to statically initialize constant bounds.
+
+    This function is used to create special bound values.  For now
+    only INIT bounds and NONE bounds are expected.  More special
+    values may be added later.  */
+
+static tree
+ix86_make_bounds_constant (HOST_WIDE_INT lb, HOST_WIDE_INT ub)
+{
+  tree low = lb ? build_minus_one_cst (pointer_sized_int_node)
+    : build_zero_cst (pointer_sized_int_node);
+  tree high = ub ? build_zero_cst (pointer_sized_int_node)
+    : build_minus_one_cst (pointer_sized_int_node);
+
+  /* This function is supposed to be used to create INIT and
+     NONE bounds only.  */
+  gcc_assert ((lb == 0 && ub == -1)
+	      || (lb == -1 && ub == 0));
+
+  return build_complex (NULL, low, high);
+}
+
+/* Generate a list of statements STMTS to initialize pointer bounds
+   variable VAR with bounds LB and UB.  Return the number of generated
+   statements.  */
+
+static int
+ix86_initialize_bounds (tree var, tree lb, tree ub, tree *stmts)
+{
+  tree bnd_ptr = build_pointer_type (pointer_sized_int_node);
+  tree lhs, modify, var_p;
+
+  ub = build1 (BIT_NOT_EXPR, pointer_sized_int_node, ub);
+  var_p = fold_convert (bnd_ptr, build_fold_addr_expr (var));
+
+  lhs = build1 (INDIRECT_REF, pointer_sized_int_node, var_p);
+  modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, lb);
+  append_to_statement_list (modify, stmts);
+
+  lhs = build1 (INDIRECT_REF, pointer_sized_int_node,
+		build2 (POINTER_PLUS_EXPR, bnd_ptr, var_p,
+			TYPE_SIZE_UNIT (pointer_sized_int_node)));
+  modify = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, ub);
+  append_to_statement_list (modify, stmts);
+
+  return 2;
+}
+
 /* Initialize the GCC target structure.  */
 #undef TARGET_RETURN_IN_MEMORY
 #define TARGET_RETURN_IN_MEMORY ix86_return_in_memory
@@ -47897,6 +48197,33 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree *clear, tree *update)
 #undef TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS
 #define TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS true
 
+#undef TARGET_LOAD_BOUNDS_FOR_ARG
+#define TARGET_LOAD_BOUNDS_FOR_ARG ix86_load_bounds
+
+#undef TARGET_STORE_BOUNDS_FOR_ARG
+#define TARGET_STORE_BOUNDS_FOR_ARG ix86_store_bounds
+
+#undef TARGET_LOAD_RETURNED_BOUNDS
+#define TARGET_LOAD_RETURNED_BOUNDS ix86_load_returned_bounds
+
+#undef TARGET_STORE_RETURNED_BOUNDS
+#define TARGET_STORE_RETURNED_BOUNDS ix86_store_returned_bounds
+
+#undef TARGET_CHKP_BOUND_MODE
+#define TARGET_CHKP_BOUND_MODE ix86_mpx_bound_mode
+
+#undef TARGET_BUILTIN_CHKP_FUNCTION
+#define TARGET_BUILTIN_CHKP_FUNCTION ix86_builtin_mpx_function
+
+#undef TARGET_CHKP_FUNCTION_VALUE_BOUNDS
+#define TARGET_CHKP_FUNCTION_VALUE_BOUNDS ix86_function_value_bounds
+
+#undef TARGET_CHKP_MAKE_BOUNDS_CONSTANT
+#define TARGET_CHKP_MAKE_BOUNDS_CONSTANT ix86_make_bounds_constant
+
+#undef TARGET_CHKP_INITIALIZE_BOUNDS
+#define TARGET_CHKP_INITIALIZE_BOUNDS ix86_initialize_bounds
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-i386.h"