[google] Add attributes: always_patch_for_instrumentation and never_patch_for_instrumentation (issue6821051)
Harshit Chopra
harshit@google.com
Mon Nov 5 20:20:00 GMT 2012
2012-11-05 Harshit Chopra <harshit@google.com>
* gcc/c-family/c-common.c (handle_always_patch_for_instrumentation_attribute): Handle
always_patch_for_instrumentation attribute and turn inlining off for the function.
(handle_never_patch_for_instrumentation_attribute): Handle
never_patch_for_instrumentation attribute of a function.
* gcc/config/i386/i386.c (has_attribute): Checks the presence of an attribute.
(check_should_patch_current_function): Takes into account
always_patch_for_instrumentation or never_patch_for_instrumentation attribute
when deciding that a function should be patched.
* gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c (int main): Test case
to test for never_patch_for_instrumentation attribute.
* gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c: Test case to test for
always_patch_for_instrumentation attribute.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index ab416ff..04b973f 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -396,6 +396,13 @@ static tree ignore_attribute (tree *, tree, tree, int, bool *);
static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
+static tree handle_always_patch_for_instrumentation_attribute (tree *, tree,
+ tree, int,
+ bool *);
+static tree handle_never_patch_for_instrumentation_attribute (tree *, tree,
+ tree, int,
+ bool *);
+
static void check_function_nonnull (tree, int, tree *);
static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
static bool nonnull_check_p (tree, unsigned HOST_WIDE_INT);
@@ -804,6 +811,13 @@ const struct attribute_spec c_common_attribute_table[] =
The name contains space to prevent its usage in source code. */
{ "fn spec", 1, 1, false, true, true,
handle_fnspec_attribute, false },
+ { "always_patch_for_instrumentation", 0, 0, true, false, false,
+ handle_always_patch_for_instrumentation_attribute,
+ false },
+ { "never_patch_for_instrumentation", 0, 0, true, false, false,
+ handle_never_patch_for_instrumentation_attribute,
+ false },
+
{ NULL, 0, 0, false, false, false, NULL, false }
};
@@ -9158,6 +9172,48 @@ handle_no_thread_safety_analysis_attribute (tree *node, tree name,
return NULL_TREE;
}
+/* Handle a "always_patch_for_instrumentation" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_always_patch_for_instrumentation_attribute (tree *node, tree name,
+ tree ARG_UNUSED (args),
+ int ARG_UNUSED (flags),
+ bool *no_add_attrs)
+{
+ if (TREE_CODE (*node) == FUNCTION_DECL)
+ {
+ /* Disable inlining if forced instrumentation. */
+ DECL_UNINLINABLE (*node) = 1;
+ }
+ else
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ *no_add_attrs = true;
+ }
+ return NULL_TREE;
+}
+
+
+/* Handle a "never_patch_for_instrumentation" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_never_patch_for_instrumentation_attribute (tree *node, tree name,
+ tree ARG_UNUSED (args),
+ int ARG_UNUSED (flags),
+ bool *no_add_attrs)
+{
+ if (TREE_CODE (*node) != FUNCTION_DECL)
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ *no_add_attrs = true;
+ }
+ return NULL_TREE;
+}
+
+
+
/* Check for valid arguments being passed to a function with FNTYPE.
There are NARGS arguments in the array ARGARRAY. */
void
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 6972ae6..4e0d770 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10968,6 +10968,13 @@ ix86_expand_epilogue (int style)
returns. */
static bool patch_current_function_p = false;
+static inline bool
+has_attribute (const char* attribute_name)
+{
+ return lookup_attribute (attribute_name,
+ DECL_ATTRIBUTES (current_function_decl)) != NULL;
+}
+
/* Return true if we patch the current function. By default a function
is patched if it has loops or if the number of insns is greater than
patch_functions_min_instructions (number of insns roughly translates
@@ -10983,6 +10990,13 @@ check_should_patch_current_function (void)
int num_loops = 0;
int min_functions_instructions;
+ /* If a function has an attribute forcing patching on or off, do as it
+ indicates. */
+ if (has_attribute ("always_patch_for_instrumentation"))
+ return true;
+ else if (has_attribute ("never_patch_for_instrumentation"))
+ return false;
+
/* Patch the function if it has at least a loop. */
if (!patch_functions_ignore_loops)
{
diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
new file mode 100644
index 0000000..cad6f2d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-no-patching.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
+
+/* Even complicated functions shouldn't get patched if they have the
+ never_patch_for_instrumentation attribute. */
+
+/* { dg-final { scan-assembler-not ".byte\t0xeb,0x09(.*).byte\t0x90" } } */
+/* { dg-final { scan-assembler-not "ret(.*).byte\t0x90(.*).byte\t0x90" } } */
+
+__attribute__ ((never_patch_for_instrumentation))
+int foo () {
+ volatile unsigned x = 0;
+ volatile unsigned y = 1;
+ x += y;
+ x *= y;
+ while (++x)
+ foo ();
+ return y;
+}
+
+
+int main ()
+{
+ int x = 0;
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c b/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c
new file mode 100644
index 0000000..86ad159
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/patch-functions-force-patching.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O3 -mpatch-functions-for-instrumentation -mno-patch-functions-main-always" } */
+
+/* Functions which have the always_patch attribute should be patched no matter
+ what. Check that there are nop-bytes at the beginning and end of the
+ function. We add -O3 so that the compiler will try to inline foo (but it
+ will be blocked by the attribute). */
+
+/* { dg-final { scan-assembler ".byte\t0xeb,0x09(.*).byte\t0x90" } } */
+/* { dg-final { scan-assembler "ret(.*).byte\t0x90(.*).byte\t0x90" } } */
+
+__attribute__ ((always_patch_for_instrumentation))
+static int foo () {
+ return 3;
+}
+
+int main () {
+ volatile int x = foo ();
+}
--
This patch is available for review at http://codereview.appspot.com/6821051
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