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.
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check to confirm there are no surprises, and with the cc1plus
of a cross-compiler to powerpc64-linux-gnu to confirm the new test
case no longer ICEs. Ok for mainline?
2022-03-12 Roger Sayle <ro...@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.
Thanks in advance,
Roger
--
diff --git a/gcc/calls.cc b/gcc/calls.cc
index 50fa7b8..1ca96e7 100644
--- 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
