Compiler Bug: no definitions

[fruffy]

The following program causes a crash with version:

fruffy@fruffy /m/w/P/p4_tv (master) [1]> p4c/build/p4c --version                             
p4c/build/p4c 
Version 1.2.0 (SHA: bdf588b61 BUILD: RELEASE)

action do_global_action(in bool make_zero, out bool val_undefined) {
    bit<16> tmp;
    tmp = tmp *  (make_zero ? 16w0: 16w1);
}
control ingress(inout Headers h, inout Meta m, inout standard_metadata_t sm) {
    bool filler_bool = true;
    bool tmp_bool = false;
    action do_action() {
        do_global_action(tmp_bool, tmp_bool);
    }

    table simple_table {
        key = {
            h.eth_hdr.src_addr : exact;
        }
        actions = {
            do_action();
            do_global_action(true, filler_bool);
        }
    }
    apply {
        simple_table.apply();
    }
}

Output:

FrontEnd_31_SimplifyControlFlow
FrontEnd_32_MoveDeclarations
P4::TypeChecking_0_ResolveReferences
P4::TypeChecking_1_TypeInference
SimplifyDefUse_0_TypeChecking
bugs/crash/bools_and_globals.p4(19): [--Wwarn=uninitialized_use] warning: tmp may be uninitialized
    tmp = tmp * (make_zero ? 16w0: 16w1);
          ^^^
bugs/crash/bools_and_globals.p4(17): [--Wwarn=uninitialized_out_param] warning: out parameter val_undefined may be uninitialized when do_global_action terminates
action do_global_action(in bool make_zero, out bool val_undefined) {
                                                    ^^^^^^^^^^^^^
bugs/crash/bools_and_globals.p4(17)
action do_global_action(in bool make_zero, out bool val_undefined) {
       ^^^^^^^^^^^^^^^^
In file: p4_tv/p4c/frontends/p4/def_use.h:351
�[31mCompiler Bug�[0m: no definitions found for tmp

running cc -E -C -undef -nostdinc -x assembler-with-cpp -I p4_tv/p4c/build/p4include -o ./bools_and_globals.p4i bugs/crash/bools_and_globals.p4
running p4_tv/p4c/build/p4c-bm2-ss -I p4_tv/p4c/build/p4include --p4v=16 -vvv -o ./bools_and_globals.json ./bools_and_globals.p4i --arch v1model

bools_and_globals.p4.txt

[hesingh]

The def_use pass should add smarts to detect that a null definition is caused because the variable is inside an action. Or the pass should just elide all the code inside the action because the local computation is useless when the action exits.