[PATCH] fix pdp11_expand_epilogue (PR target/107841)

[Mikael Pettersson via Gcc-patches]

If the stack frame only contains an alloca area, then
pdp11_expand_epilogue fails to deallocate it, resulting
in callee-saved registers and the return address being
restored from the wrong stack slots.  Fixed by adding
|| cfun->calls_alloca to the condition for deallocating
the frame.

Tested with a cross to pdp11-unknown-aout.

Ok for master? (Note: I don't have commit rights.)

gcc/

        PR target/107841
        * config/pdp11/pdp11.c (pdp11_expand_epilogue): Also
        deallocate alloca-only frame.

gcc/testsuite/

        PR target/107841
        * gcc.target/pdp11/pr107841.c: New test.
---
 gcc/config/pdp11/pdp11.cc                 |  2 +-
 gcc/testsuite/gcc.target/pdp11/pr107841.c | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/pdp11/pr107841.c

diff --git a/gcc/config/pdp11/pdp11.cc b/gcc/config/pdp11/pdp11.cc
index f6dd841f184..311a1d225e0 100644
--- a/gcc/config/pdp11/pdp11.cc
+++ b/gcc/config/pdp11/pdp11.cc
@@ -393,7 +393,7 @@ pdp11_expand_epilogue (void)
   rtx x, reg, via_ac = NULL;
 
   /* Deallocate the local variables.  */
-  if (fsize)
+  if (fsize || cfun->calls_alloca)
     {
       if (frame_pointer_needed)
        {
diff --git a/gcc/testsuite/gcc.target/pdp11/pr107841.c 
b/gcc/testsuite/gcc.target/pdp11/pr107841.c
new file mode 100644
index 00000000000..a363c468b0b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/pdp11/pr107841.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+/* Verify that the stack frame is deallocated using the frame pointer.  */
+
+void qq (int a)
+{
+    char *s = __builtin_alloca (128);
+    __builtin_sprintf (s, "qq %d", 3);
+}
+
+/* { dg-final { scan-assembler "mov\tr5,sp" } } */
-- 
2.41.0