[Mesa-dev] [PATCH] nir: only override previous alu during loop analysis if supported

[Timothy Arceri]

Users of this function expect alu to be a supported comparision
if the induction variable is not NULL. Since we attempt to
override the return values if the first limit is not a const, we
must make sure we are dealing with a valid comparision before
overriding the alu instruction.

Fixes an unreachable in inverse_comparison() with the game
Assasins Creed Odyssey.

Fixes: 3235a942c16b ("nir: find induction/limit vars in iand instructions")
---
 src/compiler/nir/nir_loop_analyze.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_loop_analyze.c b/src/compiler/nir/nir_loop_analyze.c
index c8304611b28..cb71a55f2f1 100644
--- a/src/compiler/nir/nir_loop_analyze.c
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -847,9 +847,11 @@ try_find_trip_count_vars_in_iand(nir_alu_instr **alu,
        !is_var_constant(*limit)) {
       src = iand->src[1].src.ssa;
       if (src->parent_instr->type == nir_instr_type_alu) {
-         *alu = nir_instr_as_alu(src->parent_instr);
-         if (is_supported_terminator_condition(*alu))
+         nir_alu_instr *tmp_alu = nir_instr_as_alu(src->parent_instr);
+         if (is_supported_terminator_condition(tmp_alu)) {
+            *alu = tmp_alu;
             *limit_rhs = get_induction_and_limit_vars(*alu, ind, limit, state);
+         }
       }
    }
 }
-- 
2.20.1