https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107841
Bug ID: 107841
Summary: Incorrect generation of the function's epilogue code
when there is a _builtin_alloca call.
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: avo2000 at mail dot ru
Target Milestone: ---
Incorrect generation of the function's epilogue code when there is a
_builtin_alloca call. The stack pointer is being restored incorrectly. The
function of the epilogue code generator pdp11_expand_epilogue () does not
handle the situation of having an alloca call.
Proposed solution:
--- pdp11.cc.bak 2022-08-19 11:09:52.684663800 +0300
+++ pdp11.cc 2022-11-23 19:09:11.908916500 +0300
@@ -392,7 +392,10 @@
HOST_WIDE_INT fsize = get_frame_size ();
unsigned regno;
rtx x, reg, via_ac = NULL;
+ int can_trust_sp_p = !cfun->calls_alloca;
+ if (can_trust_sp_p)
+ {
/* Deallocate the local variables. */
if (fsize)
{
@@ -405,6 +408,14 @@
emit_insn (gen_addhi3 (stack_pointer_rtx, stack_pointer_rtx,
GEN_INT (fsize)));
}
+ }
+ else
+ /* Deallocate the areas allocated using the alloca call and local variables.
*/
+ {
+ /* Deallocate the frame with a single move. */
+ gcc_assert (frame_pointer_needed);
+ emit_move_insn (stack_pointer_rtx, frame_pointer_rtx);
+ }
/* Restore the FPU registers. */
if (pdp11_saved_regno (AC4_REGNUM) || pdp11_saved_regno (AC5_REGNUM))
