8903: Skip gas accounting for fake rows

barretenberg/cpp/pil/avm/gas.pil

@@ -48,15 +48,32 @@ namespace main(256);
     pol commit abs_l2_rem_gas;
     pol commit abs_da_rem_gas;
 
+    // TODO(8945): Temporary workaround until we remove fake rows
+    // A boolean to toggle "fake" rows in main trace. It serves to remove them from gas accounting.
+    // The values in l2/da_gas_remaining will not change on such rows.
+    // Once all fake rows are removed, we can replace is_gas_accounted by sel_execution_row in all relations below.
+    pol commit is_fake_row;
+    pol commit is_gas_accounted;
+    #[IS_GAS_ACCOUNTED]
+    is_gas_accounted = (1 - is_fake_row) * sel_execution_row;
+
     // Boolean constraints
     l2_out_of_gas * (1 - l2_out_of_gas) = 0;
     da_out_of_gas * (1 - da_out_of_gas) = 0;
+    // TODO(8945): clean up fake row related code
+    is_fake_row * (1 - is_fake_row) = 0; // Temporary
+
+    //TODO(8945): clean up fake row related code
+    #[L2_GAS_NO_DECREMENT_FAKE_ROW]
+    is_fake_row * (l2_gas_remaining - l2_gas_remaining') = 0;
+    #[DA_GAS_NO_DECREMENT_FAKE_ROW]
+    is_fake_row * (da_gas_remaining - da_gas_remaining') = 0;
 
     // Constrain that the gas decrements correctly per instruction
     #[L2_GAS_REMAINING_DECREMENT_NOT_CALL]
-    sel_execution_row * (1 - sel_op_external_call - sel_op_static_call) * (l2_gas_remaining' - l2_gas_remaining + base_l2_gas_op_cost + (dyn_l2_gas_op_cost * dyn_gas_multiplier)) = 0;
+    is_gas_accounted * (1 - sel_op_external_call - sel_op_static_call) * (l2_gas_remaining' - l2_gas_remaining + base_l2_gas_op_cost + (dyn_l2_gas_op_cost * dyn_gas_multiplier)) = 0;
     #[DA_GAS_REMAINING_DECREMENT_NOT_CALL]
-    sel_execution_row * (1 - sel_op_external_call - sel_op_static_call) * (da_gas_remaining' - da_gas_remaining + base_da_gas_op_cost + (dyn_da_gas_op_cost * dyn_gas_multiplier)) = 0;
+    is_gas_accounted * (1 - sel_op_external_call - sel_op_static_call) * (da_gas_remaining' - da_gas_remaining + base_da_gas_op_cost + (dyn_da_gas_op_cost * dyn_gas_multiplier)) = 0;
     // We need to special-case external calls since the gas cost format is
     // base_l2 + nested_call_cost + dyn_gas_cost * dyn_gas_multiplier.
     // TODO: Unconstrained until CALL is properly implemented.
@@ -67,11 +84,11 @@ namespace main(256);
 
     // Prove that XX_out_of_gas == 0 <==> XX_gas_remaining' >= 0
     // TODO: Ensure that remaining gas values are initialized as u32 and that gas l2_gas_op_cost/da_gas_op_cost are u32.
-    sel_execution_row * ((1 - 2 * l2_out_of_gas) * l2_gas_remaining' - abs_l2_rem_gas) = 0;
-    sel_execution_row * ((1 - 2 * da_out_of_gas) * da_gas_remaining' - abs_da_rem_gas) = 0;
+    is_gas_accounted * ((1 - 2 * l2_out_of_gas) * l2_gas_remaining' - abs_l2_rem_gas) = 0;
+    is_gas_accounted * ((1 - 2 * da_out_of_gas) * da_gas_remaining' - abs_da_rem_gas) = 0;
 
     #[LOOKUP_OPCODE_GAS]
-    sel_execution_row {opcode_val, base_l2_gas_op_cost, base_da_gas_op_cost, dyn_l2_gas_op_cost, dyn_da_gas_op_cost}
+    is_gas_accounted {opcode_val, base_l2_gas_op_cost, base_da_gas_op_cost, dyn_l2_gas_op_cost, dyn_da_gas_op_cost}
     in
     gas.sel_gas_cost {clk, gas.base_l2_gas_fixed_table, gas.base_da_gas_fixed_table, gas.dyn_l2_gas_fixed_table, gas.dyn_da_gas_fixed_table};
 
@@ -80,10 +97,10 @@ namespace main(256);
     #[PERM_RNG_GAS_L2]
     range_check.gas_l2_rng_chk {range_check.clk, range_check.value}
     is
-    main.sel_execution_row {main.clk, main.abs_l2_rem_gas };
+    is_gas_accounted {main.clk, main.abs_l2_rem_gas };
 
     #[PERM_RNG_GAS_DA]
     range_check.gas_da_rng_chk {range_check.clk, range_check.value}
     is
-    main.sel_execution_row {main.clk, main.abs_da_rem_gas };
+    is_gas_accounted {main.clk, main.abs_da_rem_gas };
 

barretenberg/cpp/src/barretenberg/vm/avm/generated/circuit_builder.cpp

@@ -193,6 +193,8 @@ AvmCircuitBuilder::ProverPolynomials AvmCircuitBuilder::compute_polynomials() co
                 polys.main_ind_addr_d.set_if_valid_index(i, rows[i].main_ind_addr_d);
                 polys.main_internal_return_ptr.set_if_valid_index(i, rows[i].main_internal_return_ptr);
                 polys.main_inv.set_if_valid_index(i, rows[i].main_inv);
+                polys.main_is_fake_row.set_if_valid_index(i, rows[i].main_is_fake_row);
+                polys.main_is_gas_accounted.set_if_valid_index(i, rows[i].main_is_gas_accounted);
                 polys.main_kernel_in_offset.set_if_valid_index(i, rows[i].main_kernel_in_offset);
                 polys.main_kernel_out_offset.set_if_valid_index(i, rows[i].main_kernel_out_offset);
                 polys.main_l1_to_l2_msg_exists_write_offset.set_if_valid_index(