PR middle-end/104885: Fix ICE with large stack frame on powerpc64.

My recent testcase for PR c++/84964.C stress tests the middle-end by
attempting to pass a UINT_MAX sized structure on the stack.  Although
my fix to PR84964 avoids the ICE after sorry on x86_64 and similar
targets, a related issue still exists on powerpc64 (and similar
ACCUMULATE_OUTGOING_ARGS/ARGS_GROW_DOWNWARD targets) which don't
issue a "sorry, unimplemented" message, but instead ICE elsewhere.

After attempting several alternate fixes, the simplest solution is
to just defensively check in mark_stack_region_used that the upper
bound of the region lies within the allocated stack_usage_map
array, which is of size highest_outgoing_arg_in_use.  When this isn't
the case, the code now follows the same path as for variable sized
regions, and uses stack_usage_watermark rather than a map.

2022-03-26  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR middle-end/104885
	* calls.cc (mark_stack_region_used): Check that the region
	is within the allocated size of stack_usage_map.

diff --git a/gcc/calls.cc b/gcc/calls.cc
index e13469c..4d0bc45 100644 (file)
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -201,7 +201,8 @@ mark_stack_region_used (poly_uint64 lower_bound, poly_uint64 upper_bound)
 {
   unsigned HOST_WIDE_INT const_lower, const_upper;
   const_lower = constant_lower_bound (lower_bound);
-  if (upper_bound.is_constant (&const_upper))
+  if (upper_bound.is_constant (&const_upper)
+      && const_upper <= highest_outgoing_arg_in_use)
     for (unsigned HOST_WIDE_INT i = const_lower; i < const_upper; ++i)
       stack_usage_map[i] = 1;
   else