s390.c (s390_hotpatch_trampoline_halfwords_default): New constant

2013-12-19  Dominik Vogt  <vogt@linux.vnet.ibm.com>
	    Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* config/s390/s390.c (s390_hotpatch_trampoline_halfwords_default): New
	constant
	(s390_hotpatch_trampoline_halfwords_max): New constant
	(s390_hotpatch_trampoline_halfwords): New static variable
	(get_hotpatch_attribute): New function
	(s390_handle_hotpatch_attribute): New function
	(s390_attribute_table): New target specific attribute table to implement
	the hotpatch attribute
	(s390_option_override): Parse hotpatch options
	(s390_function_num_hotpatch_trampoline_halfwords): New function
	(s390_can_inline_p): Implement target hook to
	suppress hotpatching for explicitly inlined functions
	(s390_asm_output_function_label): Generate hotpatch prologue
	(TARGET_ATTRIBUTE_TABLE): Define to implement target attribute table
	(TARGET_CAN_INLINE_P): Define to implement target hook
	* config/s390/s390.opt (mhotpatch): New options -mhotpatch, -mhotpatch=
	* config/s390/s390-protos.h (s390_asm_output_function_label): Add
	prototype
	* config/s390/s390.h (ASM_OUTPUT_FUNCTION_LABEL): Target specific
	function label generation for hotpatching
	(FUNCTION_BOUNDARY): Align functions to eight bytes
	* doc/extend.texi: Document hotpatch attribute
	* doc/invoke.texi: Document -mhotpatch option

2013-12-19  Dominik Vogt  <vogt@linux.vnet.ibm.com>
	    Andreas Krebbel  <Andreas.Krebbel@de.ibm.com>

	* gcc/testsuite/gcc.target/s390/hotpatch-1.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-2.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-3.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-4.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-5.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-6.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-7.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-8.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-9.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-10.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-11.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-12.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-1.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-2.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-3.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-4.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-5.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-6.c: New test
	* gcc/testsuite/gcc.target/s390/hotpatch-compile-7.c: New test



Co-Authored-By: Andreas Krebbel <Andreas.Krebbel@de.ibm.com>

From-SVN: r206111

4 files changed, 214 insertions, 1 deletions

diff --git a/gcc/config/s390/s390-protos.h b/gcc/config/s390/s390-protos.h
index 67283df..7b43ed0 100644
--- a/gcc/config/s390/s390-protos.h
+++ b/gcc/config/s390/s390-protos.h
@@ -110,5 +110,6 @@ extern bool s390_decompose_shift_count (rtx, rtx *, HOST_WIDE_INT *);
 extern int s390_branch_condition_mask (rtx);
 extern int s390_compare_and_branch_condition_mask (rtx);
 extern bool s390_extzv_shift_ok (int, int, unsigned HOST_WIDE_INT);
+extern void s390_asm_output_function_label (FILE *, const char *, tree);
 
 #endif /* RTX_CODE */
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index f9b7cd0..5319a69 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -434,6 +434,65 @@ struct GTY(()) machine_function
    bytes on a z10 (or higher) CPU.  */
 #define PREDICT_DISTANCE (TARGET_Z10 ? 384 : 2048)
 
+static const int s390_hotpatch_trampoline_halfwords_default = 12;
+static const int s390_hotpatch_trampoline_halfwords_max = 1000000;
+static int s390_hotpatch_trampoline_halfwords = -1;
+
+/* Return the argument of the given hotpatch attribute or the default value if
+   no argument is present.  */
+
+static inline int
+get_hotpatch_attribute (tree hotpatch_attr)
+{
+  const_tree args;
+
+  args = TREE_VALUE (hotpatch_attr);
+
+  return (args) ?
+    TREE_INT_CST_LOW (TREE_VALUE (args)):
+    s390_hotpatch_trampoline_halfwords_default;
+}
+
+/* Check whether the hotpatch attribute is applied to a function and, if it has
+   an argument, the argument is valid.  */
+
+static tree
+s390_handle_hotpatch_attribute (tree *node, tree name, tree args,
+				int flags ATTRIBUTE_UNUSED, bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FUNCTION_DECL)
+    {
+      warning (OPT_Wattributes, "%qE attribute only applies to functions",
+	       name);
+      *no_add_attrs = true;
+    }
+  else if (args)
+    {
+      tree expr = TREE_VALUE (args);
+
+      if (TREE_CODE (expr) != INTEGER_CST
+	  || !INTEGRAL_TYPE_P (TREE_TYPE (expr))
+	  || TREE_INT_CST_HIGH (expr) != 0
+	  || TREE_INT_CST_LOW (expr) > (unsigned int)
+	  s390_hotpatch_trampoline_halfwords_max)
+	{
+	  error ("requested %qE attribute is not a non-negative integer"
+		 " constant or too large (max. %d)", name,
+		 s390_hotpatch_trampoline_halfwords_max);
+	  *no_add_attrs = true;
+	}
+    }
+
+  return NULL_TREE;
+}
+
+static const struct attribute_spec s390_attribute_table[] = {
+  { "hotpatch", 0, 1, true, false, false, s390_handle_hotpatch_attribute, false
+  },
+  /* End element.  */
+  { NULL,        0, 0, false, false, false, NULL, false }
+};
+
 /* Return the alignment for LABEL.  We default to the -falign-labels
    value except for the literal pool base label.  */
 int
@@ -1622,6 +1681,46 @@ s390_init_machine_status (void)
 static void
 s390_option_override (void)
 {
+  unsigned int i;
+  cl_deferred_option *opt;
+  vec<cl_deferred_option> *v =
+    (vec<cl_deferred_option> *) s390_deferred_options;
+
+  if (v)
+    FOR_EACH_VEC_ELT (*v, i, opt)
+      {
+	switch (opt->opt_index)
+	  {
+	  case OPT_mhotpatch:
+	    s390_hotpatch_trampoline_halfwords = (opt->value) ?
+	      s390_hotpatch_trampoline_halfwords_default : -1;
+	    break;
+	  case OPT_mhotpatch_:
+	    {
+	      int val;
+
+	      val = integral_argument (opt->arg);
+	      if (val == -1)
+		{
+		  /* argument is not a plain number */
+		  error ("argument to %qs should be a non-negative integer",
+			 "-mhotpatch=");
+		  break;
+		}
+	      else if (val > s390_hotpatch_trampoline_halfwords_max)
+		{
+		  error ("argument to %qs is too large (max. %d)",
+			 "-mhotpatch=", s390_hotpatch_trampoline_halfwords_max);
+		  break;
+		}
+	      s390_hotpatch_trampoline_halfwords = val;
+	      break;
+	    }
+	  default:
+	    gcc_unreachable ();
+	  }
+      }
+
   /* Set up function hooks.  */
   init_machine_status = s390_init_machine_status;
 
@@ -5347,6 +5446,102 @@ get_some_local_dynamic_name (void)
   gcc_unreachable ();
 }
 
+/* Returns -1 if the function should not be made hotpatchable.  Otherwise it
+   returns a number >= 0 that is the desired size of the hotpatch trampoline
+   in halfwords. */
+
+static int s390_function_num_hotpatch_trampoline_halfwords (tree decl,
+							    bool do_warn)
+{
+  tree attr;
+
+  if (DECL_DECLARED_INLINE_P (decl)
+      || DECL_ARTIFICIAL (decl)
+      || MAIN_NAME_P (DECL_NAME (decl)))
+    {
+      /* - Explicitly inlined functions cannot be hotpatched.
+	 - Artificial functions need not be hotpatched.
+	 - Making the main function hotpatchable is useless. */
+      return -1;
+    }
+  attr = lookup_attribute ("hotpatch", DECL_ATTRIBUTES (decl));
+  if (attr || s390_hotpatch_trampoline_halfwords >= 0)
+    {
+      if (lookup_attribute ("always_inline", DECL_ATTRIBUTES (decl)))
+	{
+	  if (do_warn)
+	    warning (OPT_Wattributes, "function %qE with the %qs attribute"
+		     " is not hotpatchable", DECL_NAME (decl), "always_inline");
+	  return -1;
+	}
+      else
+	{
+	  return (attr) ?
+	    get_hotpatch_attribute (attr) : s390_hotpatch_trampoline_halfwords;
+	}
+    }
+
+  return -1;
+}
+
+/* Hook to determine if one function can safely inline another.  */
+
+static bool
+s390_can_inline_p (tree caller, tree callee)
+{
+  if (s390_function_num_hotpatch_trampoline_halfwords (callee, false) >= 0)
+    return false;
+
+  return default_target_can_inline_p (caller, callee);
+}
+
+/* Write the extra assembler code needed to declare a function properly.  */
+
+void
+s390_asm_output_function_label (FILE *asm_out_file, const char *fname,
+				tree decl)
+{
+  int hotpatch_trampoline_halfwords = -1;
+
+  if (decl)
+    {
+      hotpatch_trampoline_halfwords =
+	s390_function_num_hotpatch_trampoline_halfwords (decl, true);
+      if (hotpatch_trampoline_halfwords >= 0
+	  && decl_function_context (decl) != NULL_TREE)
+	{
+	  warning_at (0, DECL_SOURCE_LOCATION (decl),
+		      "hotpatch_prologue is not compatible with nested"
+		      " function");
+	  hotpatch_trampoline_halfwords = -1;
+	}
+    }
+
+  if (hotpatch_trampoline_halfwords > 0)
+    {
+      int i;
+
+      /* Add a trampoline code area before the function label and initialize it
+	 with two-byte nop instructions.  This area can be overwritten with code
+	 that jumps to a patched version of the function.  */
+      for (i = 0; i < hotpatch_trampoline_halfwords; i++)
+	asm_fprintf (asm_out_file, "\tnopr\t%%r7\n");
+      /* Note:  The function label must be aligned so that (a) the bytes of the
+	 following nop do not cross a cacheline boundary, and (b) a jump address
+	 (eight bytes for 64 bit targets, 4 bytes for 32 bit targets) can be
+	 stored directly before the label without crossing a cacheline
+	 boundary.  All this is necessary to make sure the trampoline code can
+	 be changed atomically.  */
+    }
+
+  ASM_OUTPUT_LABEL (asm_out_file, fname);
+
+  /* Output a four-byte nop if hotpatching is enabled.  This can be overwritten
+     atomically with a relative backwards jump to the trampoline area.  */
+  if (hotpatch_trampoline_halfwords >= 0)
+    asm_fprintf (asm_out_file, "\tnop\t0\n");
+}
+
 /* Output machine-dependent UNSPECs occurring in address constant X
    in assembler syntax to stdio stream FILE.  Returns true if the
    constant X could be recognized, false otherwise.  */
@@ -11920,6 +12115,12 @@ s390_loop_unroll_adjust (unsigned nunroll, struct loop *loop)
 #undef TARGET_HARD_REGNO_SCRATCH_OK
 #define TARGET_HARD_REGNO_SCRATCH_OK s390_hard_regno_scratch_ok
 
+#undef TARGET_ATTRIBUTE_TABLE
+#define TARGET_ATTRIBUTE_TABLE s390_attribute_table
+
+#undef TARGET_CAN_INLINE_P
+#define TARGET_CAN_INLINE_P s390_can_inline_p
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-s390.h"
diff --git a/gcc/config/s390/s390.h b/gcc/config/s390/s390.h
index bca18fe..75b642b 100644
--- a/gcc/config/s390/s390.h
+++ b/gcc/config/s390/s390.h
@@ -217,7 +217,7 @@ enum processor_flags
 #define STACK_BOUNDARY 64
 
 /* Allocation boundary (in *bits*) for the code of a function.  */
-#define FUNCTION_BOUNDARY 32
+#define FUNCTION_BOUNDARY 64
 
 /* There is no point aligning anything to a rounder boundary than this.  */
 #define BIGGEST_ALIGNMENT 64
@@ -878,6 +878,9 @@ do {									\
   fputc ('\n', (FILE));							\
 } while (0)
 
+#undef ASM_OUTPUT_FUNCTION_LABEL
+#define ASM_OUTPUT_FUNCTION_LABEL(FILE, NAME, DECL) \
+  s390_asm_output_function_label (FILE, NAME, DECL)
 
 /* Miscellaneous parameters.  */
 
diff --git a/gcc/config/s390/s390.opt b/gcc/config/s390/s390.opt
index 7dedb83..ef92f46 100644
--- a/gcc/config/s390/s390.opt
+++ b/gcc/config/s390/s390.opt
@@ -96,6 +96,14 @@ mhard-float
 Target Report RejectNegative Negative(msoft-float) InverseMask(SOFT_FLOAT, HARD_FLOAT)
 Enable hardware floating point
 
+mhotpatch
+Target Report Var(s390_deferred_options) Defer
+Prepend the function label with 12 two-byte Nop instructions, and add a four byte Nop instruction after the label for hotpatching.
+
+mhotpatch=
+Target RejectNegative Report Joined Var(s390_deferred_options) Defer
+Prepend the function label with the given number of two-byte Nop instructions, and add a four byte Nop instruction after the label for hotpatching.
+
 mlong-double-128
 Target Report RejectNegative Negative(mlong-double-64) Mask(LONG_DOUBLE_128)
 Use 128-bit long double