[PATCH] Add -fno-instrument-function

[Andi Kleen <andi at firstfloor dot org>]

From: Andi Kleen <ak@linux.intel.com>

This adds a new C/C++ option to force
__attribute__((no_instrument_function)) on every function compiled.

This is useful together with LTO. You may want to have the whole
program compiled with -pg and have to specify that in the LTO
link, but want to disable it for some specific files. As the
option works on the frontend level it is already passed through
properly by LTO.

Without LTO it is equivalent to not specifing -pg or -mfentry.

This fixes some missing functionality in the Linux kernel LTO port.

Passed bootstrap and test suite on x86_64-linux. Ok?

gcc/:

2012-10-31  Andi Kleen <ak@linux.intel.com>

	* c.opt (fno-instrument-function): Document.

gcc/c:

2012-10-31  Andi Kleen <ak@linux.intel.com>

	* c-decl.c (start_function): Handle force_no_instrument_function

gcc/testsuite:

2012-10-31  Andi Kleen <ak@linux.intel.com>

	* g++.dg/fno-instrument-function.C: Add.
	* gcc.dg/fno-instrument-function.c: Add.
---
 gcc/c-family/c.opt                             |    4 ++++
 gcc/c/c-decl.c                                 |    3 +++
 gcc/doc/invoke.texi                            |    8 +++++++-
 gcc/testsuite/g++.dg/fno-instrument-function.C |   18 ++++++++++++++++++
 gcc/testsuite/gcc.dg/fno-instrument-function.c |   24 ++++++++++++++++++++++++
 5 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/fno-instrument-function.C
 create mode 100644 gcc/testsuite/gcc.dg/fno-instrument-function.c

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 7eb66c6..62dfc57 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -967,6 +967,10 @@ fnil-receivers
 ObjC ObjC++ Var(flag_nil_receivers) Init(1)
 Assume that receivers of Objective-C messages may be nil
 
+fno-instrument-function
+C C++ ObjC ObjC++ RejectNegative Report Var(force_no_instrument_function)
+Force __attribute__((no_instrument_function)) for all functions in translation unit.
+
 fnonansi-builtins
 C++ ObjC++ Var(flag_no_nonansi_builtin, 0)
 
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 80867ca..fe957ab 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -7875,6 +7875,9 @@ start_function (struct c_declspecs *declspecs, struct c_declarator *declarator,
   if (current_scope == file_scope)
     maybe_apply_pragma_weak (decl1);
 
+  if (force_no_instrument_function)
+    DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (decl1) = 1;  
+
   /* Warn for unlikely, improbable, or stupid declarations of `main'.  */
   if (warn_main && MAIN_NAME_P (DECL_NAME (decl1)))
     {
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 15ecaf1..dbabc72 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -174,7 +174,7 @@ in the following sections.
 -aux-info @var{filename} -fallow-parameterless-variadic-functions @gol
 -fno-asm  -fno-builtin  -fno-builtin-@var{function} @gol
 -fhosted  -ffreestanding -fopenmp -fms-extensions -fplan9-extensions @gol
--trigraphs  -traditional  -traditional-cpp @gol
+-trigraphs  -traditional  -traditional-cpp -fno-instrument-function @gol
 -fallow-single-precision  -fcond-mismatch -flax-vector-conversions @gol
 -fsigned-bitfields  -fsigned-char @gol
 -funsigned-bitfields  -funsigned-char}
@@ -1858,6 +1858,12 @@ Allow implicit conversions between vectors with differing numbers of
 elements and/or incompatible element types.  This option should not be
 used for new code.
 
+@item -fno-instrument-function
+@opindex fno-instrument-function
+Override @option{-pg} for this translation unit. This is useful with
+Link Time Optimization (LTO) to override the effects of -pg for a 
+specific source file.
+
 @item -funsigned-char
 @opindex funsigned-char
 Let the type @code{char} be unsigned, like @code{unsigned char}.
diff --git a/gcc/testsuite/g++.dg/fno-instrument-function.C b/gcc/testsuite/g++.dg/fno-instrument-function.C
new file mode 100644
index 0000000..b15cd94
--- /dev/null
+++ b/gcc/testsuite/g++.dg/fno-instrument-function.C
@@ -0,0 +1,18 @@
+/* Test -fno-instrument-function */
+/* { dg-do compile } */
+/* { dg-options "-fno-instrument-function" } */
+/* { dg-final { scan-assembler-not "mcount" } } */
+/* Origin: Andi Kleen */
+extern void foobar(const char *);
+
+void func(void)
+{
+  foobar ("Hello world\n");
+}
+
+void func2(void)
+{
+  int i;
+  for (i = 0; i < 10; i++)
+    foobar ("Hello world");
+}
diff --git a/gcc/testsuite/gcc.dg/fno-instrument-function.c b/gcc/testsuite/gcc.dg/fno-instrument-function.c
new file mode 100644
index 0000000..4fafe4f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fno-instrument-function.c
@@ -0,0 +1,24 @@
+/* Test -fno-instrument-function */
+/* { dg-do compile } */
+/* { dg-options "-fno-instrument-function" } */
+/* { dg-final { scan-assembler-not "mcount" } } */
+/* Origin: Andi Kleen */
+extern void foobar(char *);
+
+void func(void)
+{
+  foobar ("Hello world\n");
+}
+
+void func2(void)
+{
+  int i;
+  for (i = 0; i < 10; i++)
+    foobar ("Hello world");
+}
+
+void func3(a)
+char *a;
+{
+  foobar("Hello world");
+}
-- 
1.7.10.4