From 710a2a45c4d3d8fa8d984c2371a0a1ae44d3fe93 Mon Sep 17 00:00:00 2001
From: Stan Cox <scox@redhat.com>
Date: Thu, 21 Apr 2011 16:04:24 -0400
Subject: [PATCH] Add -DSTAP_SDT_ARG_CONSTRAINT

    * sdt.h (STAP_SDT_ARG_CONSTRAINT): Allow override of default nor constraint.
    * cxxclass.exp: Use it.
---
 NEWS                                  | 5 +++++
 includes/sys/sdt.h                    | 7 ++++++-
 testsuite/systemtap.base/cxxclass.exp | 4 ++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 4b449d6e3..34c7fabbb 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,10 @@
 * What's new in version 1.5
 
+- Compiler optimization may sometimes result in systemtap not being able to
+  access a user-space probe argument.  Compiling the application with
+  -DSTAP_SDT_ARG_CONSTRAINT=nr will force the argument to be an immediate or
+  register value which should enable systemtap to access the argument.
+
 - GNU Gettext has now been intergrated with systemtap.  Our translation
   page can be found at http://www.transifex.net/projects/p/systemtap/ .
   "make update-po" will generate the necessary files to use translated
diff --git a/includes/sys/sdt.h b/includes/sys/sdt.h
index 101a6a7e2..f7e136039 100644
--- a/includes/sys/sdt.h
+++ b/includes/sys/sdt.h
@@ -45,9 +45,14 @@
 # define _SDT_ASM_STRING_1(x)		_SDT_ASM_1(.asciz #x)
 
 # define _SDT_ARGFMT(no)		%n[_SDT_S##no]@_SDT_ARGTMPL(_SDT_A##no)
+# ifndef STAP_SDT_ARG_CONSTRAINT
+# define STAP_SDT_ARG_CONSTRAINT        nor
+# endif
+# define _SDT_STRINGIFY(x)              #x
+# define _SDT_ARG_CONSTRAINT_STRING(x)  _SDT_STRINGIFY(x)
 # define _SDT_ARG(n, x)			\
   [_SDT_S##n] "n" ((_SDT_ARGSIGNED (x) ? 1 : -1) * (int) _SDT_ARGSIZE (x)), \
-  [_SDT_A##n] "nor" (_SDT_ARGVAL (x))
+  [_SDT_A##n] _SDT_ARG_CONSTRAINT_STRING (STAP_SDT_ARG_CONSTRAINT) (_SDT_ARGVAL (x))
 #endif
 #define _SDT_ASM_STRING(x)		_SDT_ASM_STRING_1(x)
 
diff --git a/testsuite/systemtap.base/cxxclass.exp b/testsuite/systemtap.base/cxxclass.exp
index 3b73c245c..c74d68030 100644
--- a/testsuite/systemtap.base/cxxclass.exp
+++ b/testsuite/systemtap.base/cxxclass.exp
@@ -14,6 +14,10 @@ set test_flags "additional_flags=-g"
 set test_flags "$test_flags additional_flags=-O2"
 set test_flags "$test_flags [sdt_includes]"
 set test_flags "$test_flags compiler=g++"
+# ppc64 needs a more restrictive constraint for the probe args
+if {[regexp "^(x86_64|i.86)$" $::tcl_platform(machine)] == 0} {
+set test_flags "$test_flags additional_flags=-DSTAP_SDT_ARG_CONSTRAINT=nr"
+}
 
 set res [target_compile $srcdir/$subdir/$test.cxx $test.exe executable "$test_flags"]
 if { $res != "" } {
-- 
2.43.5