From 50c9d049978e096b754415819c521c9d9504173e Mon Sep 17 00:00:00 2001
From: Richard Earnshaw <rearnsha@arm.com>
Date: Thu, 22 Dec 2011 14:13:09 +0000
Subject: [PATCH] re PR target/51643 (Incorrect code produced for tail-call of
 weak function with -O2/-O3 option)

	PR target/51643
	* arm.c (arm_function_ok_for_sibcall): Don't try to tailcall a
	weak function on bare-metal EABI targets.

	* gcc.target/arm/sibcall-2.c: New test.

From-SVN: r182621
---
 gcc/ChangeLog                            |  6 ++++++
 gcc/config/arm/arm.c                     |  8 ++++++++
 gcc/testsuite/ChangeLog                  |  5 +++++
 gcc/testsuite/gcc.target/arm/sibcall-2.c | 12 ++++++++++++
 4 files changed, 31 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/arm/sibcall-2.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a26d8b4f2c67..d1c9a2f62536 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/51643
+	* arm.c (arm_function_ok_for_sibcall): Don't try to tailcall a
+	weak function on bare-metal EABI targets.
+
 2011-12-21  Jonathan Wakely  <jwakely.gcc@gmail.com>
 	    Jim Avera  <james_avera@yahoo.com>
 
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index b682a9f0d9df..fec43fba9039 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -5250,6 +5250,14 @@ arm_function_ok_for_sibcall (tree decl, tree exp)
   if (IS_STACKALIGN (func_type))
     return false;
 
+  /* The AAPCS says that, on bare-metal, calls to unresolved weak
+     references should become a NOP.  Don't convert such calls into
+     sibling calls.  */
+  if (TARGET_AAPCS_BASED
+      && arm_abi == ARM_ABI_AAPCS
+      && lookup_attribute ("weak", DECL_ATTRIBUTES (decl)))
+    return false;
+
   /* Everything else is ok.  */
   return true;
 }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 18db669dcb9d..9e58adc714ca 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-12-21  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR target/51643
+	* gcc.target/arm/sibcall-2.c: New test.
+
 2011-12-22  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR testsuite/51645
diff --git a/gcc/testsuite/gcc.target/arm/sibcall-2.c b/gcc/testsuite/gcc.target/arm/sibcall-2.c
new file mode 100644
index 000000000000..921c0f30284b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/sibcall-2.c
@@ -0,0 +1,12 @@
+/* { dg-require-effective-target arm_eabi } */
+/* { dg-do compile } */
+/* { dg-options "-O2 -mabi=aapcs" } */
+
+
+extern void __attribute__((weak)) wfunc(void);
+void main(void)
+{
+  wfunc();  /* Must not tail-call.  */
+}
+
+/* { dg-final { scan-assembler-not "b\[\\t \]+wfunc" } } */