From b6cbdbd62e15411f79d7b0df3bd080deb4000ae2 Mon Sep 17 00:00:00 2001
From: Richard Lowe <richlowe@richlowe.net>
Date: Sun, 30 Sep 2012 16:44:14 -0400
Subject: allow the global disabling of function cloning

Optimizations which clone functions to create call-specific implementations
which may be better optimized also dissociate these functions from their
symbol names in ways harmful to tracing and debugging (since there are now
several implementations of a single source symbol, quite possibly none of them
having the actual source symbol name).

This allows any function cloning to be disabled, and makes any such
optimization ineffective, and our source safe for debuggers everywhere.
---
 gcc/attribs.c       |  9 +++++++++
 gcc/common.opt      |  5 +++++
 gcc/doc/invoke.texi | 10 ++++++++++
 3 files changed, 24 insertions(+)

diff --git a/gcc/attribs.c b/gcc/attribs.c
index ebc0783c439..6c754caa9f9 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -541,6 +541,15 @@
 	attributes = tree_cons (get_identifier ("no_icf"),  NULL, attributes);
     }
 
+  /* If the user passed -fno-clone-functions, all functions should be treated
+     as "noclone" */
+  if (TREE_CODE (*node) == FUNCTION_DECL
+      && !flag_clone_functions)
+    {
+      if (lookup_attribute ("noclone", attributes) == NULL)
+	attributes = tree_cons (get_identifier ("noclone"),  NULL, attributes);
+    }
+
   targetm.insert_attributes (*node, &attributes);
 
   /* Note that attributes on the same declaration are not necessarily
diff --git a/gcc/common.opt b/gcc/common.opt
index 6dfce7eb42d..f00008e02f3 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1153,6 +1153,11 @@ fcode-hoisting
 Common Var(flag_code_hoisting) Optimization
 Enable code hoisting.
 
+fclone-functions
+Common Var(flag_clone_functions) Init(1)
+Allow the compiler to clone functions to facilitate certain optimizations.
+Enabled by default.
+
 fcombine-stack-adjustments
 Common Var(flag_combine_stack_adjustments) Optimization
 Looks for opportunities to reduce stack adjustments and stack references.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 7cb80dc7346..4f265aeead0 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -492,6 +492,7 @@
 -fassociative-math  -fauto-profile  -fauto-profile[=@var{path}] @gol
 -fauto-inc-dec  -fbranch-probabilities @gol
 -fcaller-saves @gol
+-fclone-functions
 -fcombine-stack-adjustments  -fconserve-stack @gol
 -fcompare-elim  -fcprop-registers  -fcrossjumping @gol
 -fcse-follow-jumps  -fcse-skip-blocks  -fcx-fortran-rules @gol
@@ -11129,6 +11130,15 @@
 
 Enabled by default at @option{-O1} and higher.
 
+@item -fno-clone-functions
+@opindex fno-clone-functions
+Forbid the implicit cloning of functions implicit in certain
+optimizations.  This also effectively will disable any optimization
+which wishes to clone functions, equivalent to each function having
+the ``noclone'' attribute.  This allows the prevention of the
+dissociation of a piece of text from an intelligible and expected
+symbol name, which may hamper debugging and tracing.
+
 @item -fipa-ra
 @opindex fipa-ra
 Use caller save registers for allocation if those registers are not used by