gdb/

* arm-tdep.c (thumb_analyze_prologue): Always fallback on the SP
register when the frame can't be determined.
* arm-tdep.c (arm_analyze_prologue): Ditto.

gdb/testsuite/
* gdb.arch/thumb-prologue.c (switch_stack_to_same): New test function.
(switch_stack_to_other): New test function.
* gdb.arch/thumb-prologue.exp: New test cases.

2 files changed, 61 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.arch/thumb-prologue.c b/gdb/testsuite/gdb.arch/thumb-prologue.c
index bb24df0..a726149 100644
--- a/gdb/testsuite/gdb.arch/thumb-prologue.c
+++ b/gdb/testsuite/gdb.arch/thumb-prologue.c
@@ -18,11 +18,15 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 void tpcs_frame (void);
+void switch_stack_to_same (void);
+void switch_stack_to_other (void);
 
 int
 main (void)
 {
   tpcs_frame ();
+  switch_stack_to_same ();
+  switch_stack_to_other ();
   return 0;
 }
 
@@ -104,3 +108,33 @@ asm(".text\n"
     "	mov	lr, r3\n"
     "	bx	lr\n"
 );
+
+asm(".text\n"
+    "	.align 2\n"
+    "	.thumb_func\n"
+    "	.code 16\n"
+    "write_sp:\n"
+    "	mov	sp, r0\n"
+    "	bx	lr\n"
+
+    "	.align 2\n"
+    "	.thumb_func\n"
+    "	.code 16\n"
+    "switch_stack_to_same:\n"
+    "	push	{lr}\n"
+    "	mov	r0, sp\n"
+    "	bl	write_sp\n"
+    "	pop	{r1}\n"
+    "	bx	r1\n"
+
+    "	.align 2\n"
+    "	.thumb_func\n"
+    "	.code 16\n"
+    "switch_stack_to_other:\n"
+    "	push	{lr}\n"
+    "	mov	r7, sp\n"
+    "	mov	r0, #128\n"
+    "	bl	write_sp\n"
+    "	mov	sp, r7\n"
+    "	pop	{r1}\n"
+    "	bx	r1\n");
diff --git a/gdb/testsuite/gdb.arch/thumb-prologue.exp b/gdb/testsuite/gdb.arch/thumb-prologue.exp
index e685bc5..39b61c4 100644
--- a/gdb/testsuite/gdb.arch/thumb-prologue.exp
+++ b/gdb/testsuite/gdb.arch/thumb-prologue.exp
@@ -59,3 +59,30 @@ gdb_test "backtrace 10" \
 gdb_test "info frame" \
 	".*Saved registers:.*r7 at.*r10 at.*r11 at.*lr at.*" \
 	"saved registers in TPCS"
+
+
+# Testcase for "switching" the stack to the same stack in the prologue.
+
+gdb_breakpoint "switch_stack_to_same"
+
+gdb_test "continue" "Breakpoint .*, $hex in switch_stack_to_same \\(\\)" \
+	"continue to switch_stack_to_same"
+
+gdb_test "stepi 2" "in write_sp \\(\\)" "stepi over mov sp, sp"
+
+gdb_test "backtrace 10" \
+	"#0\[ \t\]*$hex in write_sp .*\r\n#1\[ \t\]*$hex in switch_stack_to_same .*\r\n#2\[ \t\]*$hex in main.*" \
+	"backtrace in write_sp"
+
+# Testcase for switching to another stack in the prologue.
+
+gdb_breakpoint "switch_stack_to_other"
+
+gdb_test "continue" "Breakpoint .*, $hex in switch_stack_to_other \\(\\)" \
+	"continue to switch_stack_to_other"
+
+gdb_test "stepi 2" "in write_sp \\(\\)" "stepi over mov sp, 128"
+
+gdb_test "backtrace 10" \
+	"#0\[ \t\]*$hex in write_sp .*\r\n#1\[ \t\]*$hex in switch_stack_to_other .*\r\n#2\[ \t\]*$hex in main.*" \
+	"backtrace in write_sp"