[Bug tree-optimization/121345] New: [16 Regression] obvious incorrect array-bounds warning

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121345

            Bug ID: 121345
           Summary: [16 Regression] obvious incorrect array-bounds warning
           Product: gcc
           Version: 14.2.0
            Status: UNCONFIRMED
          Keywords: needs-bisection, needs-reduction, needs-source
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

While building highway with the current trunk I get:
In file included from /home/apinski/src/highway/hwy/foreach_target.h:362,
                 from
/home/apinski/src/highway/hwy/tests/foreach_vec_test.cc:18:
/home/apinski/src/highway/hwy/tests/foreach_vec_test.cc: In function ‘void
hwy::N_EMU128::{anonymous}::DoTestAllForGEVectors(const Test&) [with long
unsigned int kMinBits = 64; Test = hwy::N_EMU128::ForGEVectors<64,
TestForGEVectors>]’:
/home/apinski/src/highway/hwy/tests/foreach_vec_test.cc:337:62: error: array
subscript -32 is below array bounds of
‘hwy::N_EMU128::{anonymous}::ForeachVectorTestPerLaneSizeState [16]’
[-Werror=array-bounds=]
  337 |         &TestForGEVectorsState.per_lane_size_states[lane_size];
      |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
/home/apinski/src/highway/hwy/tests/foreach_vec_test.cc:35:37: note: while
referencing
‘hwy::N_EMU128::{anonymous}::ForeachVectorTestState::per_lane_size_states’
   35 |   ForeachVectorTestPerLaneSizeState per_lane_size_states[16];
      |                                     ^~~~~~~~~~~~~~~~~~~~


This is obvious wrong as the loop looks like:
  for (int lane_size = 1; lane_size <= kMaxSupportedLaneSize; lane_size <<= 1)
{
    ForeachVectorTestPerLaneSizeState *per_lane_size_state =
        &TestForGEVectorsState.per_lane_size_states[lane_size];

Where kMaxSupportedLaneSize is defined as:
static constexpr int kMaxSupportedLaneSize = HWY_HAVE_INTEGER64 ? 8 : 4;