C Program Control

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Chapter 5: C
C Program Control

Generating C code to effect loops, branches and the like.

§1.

void CProgramControl::initialise(code_generation_target *cgt) {
    METHOD_ADD(c_target, COMPILE_PRIMITIVE_MTID, CProgramControl::compile_primitive);
}

int CProgramControl::compile_primitive(code_generation_target *cgt, code_generation *gen,
    inter_symbol *prim_name, inter_tree_node *P) {
    inter_tree *I = gen->from;
    inter_ti bip = Primitives::to_bip(I, prim_name);

    int r = CReferences::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CArithmetic::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CMemoryModel::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CObjectModel::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CLiteralsModel::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CInputOutputModel::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    r = CConditions::compile_primitive(gen, bip, P);
    if (r != NOT_APPLICABLE) return r;
    return CProgramControl::compile_control_primitive(gen, bip, P);
}

int CProgramControl::compile_control_primitive(code_generation *gen, inter_ti bip, inter_tree_node *P) {
    int suppress_terminal_semicolon = FALSE;
    text_stream *OUT = CodeGen::current(gen);
    inter_tree *I = gen->from;
    switch (bip) {
        case PUSH_BIP:          WRITE("i7_push("); INV_A1; WRITE(")"); break;
        case PULL_BIP:          INV_A1; WRITE(" = i7_pull()"); break;
        case BREAK_BIP:         WRITE("break"); break;
        case CONTINUE_BIP:      WRITE("continue"); break;
        case RETURN_BIP:        Generate primitive for return1.1; break;
        case JUMP_BIP:          WRITE("goto "); INV_A1; break;
        case QUIT_BIP:          WRITE("exit(0)"); break;
        case RESTORE_BIP:       break;  we won't support this in C

        case INDIRECT0_BIP: case INDIRECT0V_BIP: case CALLMESSAGE0_BIP:
                                WRITE("i7_call_0("); INV_A1; WRITE(")"); break;
        case INDIRECT1_BIP: case INDIRECT1V_BIP: case CALLMESSAGE1_BIP:
                                WRITE("i7_call_1("); INV_A1; WRITE(", ");
                                INV_A2; WRITE(")"); break;
        case INDIRECT2_BIP: case INDIRECT2V_BIP: case CALLMESSAGE2_BIP:
                                WRITE("i7_call_2("); INV_A1; WRITE(", ");
                                INV_A2; WRITE(", "); INV_A3; WRITE(")"); break;
        case INDIRECT3_BIP: case INDIRECT3V_BIP: case CALLMESSAGE3_BIP:
                                WRITE("i7_call_3("); INV_A1; WRITE(", ");
                                INV_A2; WRITE(", "); INV_A3; WRITE(", "); INV_A4; WRITE(")"); break;
        case INDIRECT4_BIP: case INDIRECT4V_BIP:
                                WRITE("i7_call_4("); INV_A1; WRITE(", ");
                                INV_A2; WRITE(", "); INV_A3; WRITE(", "); INV_A4; WRITE(", ");
                                INV_A5; WRITE(")"); break;
        case INDIRECT5_BIP: case INDIRECT5V_BIP:
                                WRITE("i7_call_5("); INV_A1; WRITE(", ");
                                INV_A2; WRITE(", "); INV_A3; WRITE(", "); INV_A4; WRITE(", ");
                                INV_A5; WRITE(", "); INV_A6; WRITE(")"); break;

        case IF_BIP: Generate primitive for if1.2; break;
        case IFDEBUG_BIP: Generate primitive for ifdebug1.3; break;
        case IFSTRICT_BIP: Generate primitive for ifstrict1.4; break;
        case IFELSE_BIP: Generate primitive for ifelse1.5; break;
        case WHILE_BIP: Generate primitive for while1.6; break;
        case DO_BIP: Generate primitive for do1.7; break;
        case FOR_BIP: Generate primitive for for1.8; break;
        case OBJECTLOOP_BIP: Generate primitive for objectloop1.9; break;
        case OBJECTLOOPX_BIP: Generate primitive for objectloopx1.10; break;
        case LOOP_BIP: Generate primitive for loop1.11; break;
        case SWITCH_BIP: Generate primitive for switch1.12; break;
        case CASE_BIP: Generate primitive for case1.13; break;
        case ALTERNATIVECASE_BIP: INV_A1; WRITE(", "); INV_A2; break;
        case DEFAULT_BIP: Generate primitive for default1.14; break;

        default: internal_error("unimplemented prim");
    }
    return suppress_terminal_semicolon;
}

§1.1. Generate primitive for return1.1 =

    int rboolean = NOT_APPLICABLE;
    inter_tree_node *V = InterTree::first_child(P);
    if (V->W.data[ID_IFLD] == VAL_IST) {
        inter_ti val1 = V->W.data[VAL1_VAL_IFLD];
        inter_ti val2 = V->W.data[VAL2_VAL_IFLD];
        if (val1 == LITERAL_IVAL) {
            if (val2 == 0) rboolean = FALSE;
            if (val2 == 1) rboolean = TRUE;
        }
    }
    switch (rboolean) {
        case FALSE: WRITE("return 0"); break;
        case TRUE: WRITE("return 1"); break;
        case NOT_APPLICABLE: WRITE("return (i7val) "); CodeGen::FC::frame(gen, V); break;
    }

This code is used in §1.

§1.2. Generate primitive for if1.2 =

    WRITE("if ("); INV_A1; WRITE(") {\n"); INDENT; INV_A2;
    OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.3. Generate primitive for ifdebug1.3 =

    WRITE("#ifdef DEBUG\n"); INDENT; INV_A1; OUTDENT; WRITE("#endif\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.4. Generate primitive for ifstrict1.4 =

    WRITE("#ifdef STRICT_MODE\n"); INDENT; INV_A1; OUTDENT; WRITE("#endif\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.5. Generate primitive for ifelse1.5 =

    WRITE("if ("); INV_A1; WRITE(") {\n"); INDENT; INV_A2; OUTDENT;
    WRITE("} else {\n"); INDENT; INV_A3; OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.6. Generate primitive for while1.6 =

    WRITE("while ("); INV_A1; WRITE(") {\n"); INDENT; INV_A2; OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.7. Generate primitive for do1.7 =

    WRITE("do {"); INV_A2; WRITE("} while (!(\n"); INDENT; INV_A1; OUTDENT; WRITE("))\n");

This code is used in §1.

§1.8. Generate primitive for for1.8 =

    WRITE("for (");
    inter_tree_node *INIT = InterTree::first_child(P);
    if (!((INIT->W.data[ID_IFLD] == VAL_IST) && (INIT->W.data[VAL1_VAL_IFLD] == LITERAL_IVAL) && (INIT->W.data[VAL2_VAL_IFLD] == 1))) INV_A1;
    WRITE(";"); INV_A2;
    WRITE(";");
    inter_tree_node *U = InterTree::third_child(P);
    if (U->W.data[ID_IFLD] != VAL_IST)
    CodeGen::FC::frame(gen, U);
    WRITE(") {\n"); INDENT; INV_A4;
    OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.9. Generate primitive for objectloop1.9 =

    int in_flag = FALSE;
    inter_tree_node *U = InterTree::third_child(P);
    if ((U->W.data[ID_IFLD] == INV_IST) && (U->W.data[METHOD_INV_IFLD] == INVOKED_PRIMITIVE)) {
        inter_symbol *prim = Inter::Inv::invokee(U);
        if ((prim) && (Primitives::to_bip(I, prim) == IN_BIP)) in_flag = TRUE;
    }

    WRITE("for (i7val "); INV_A1;
    WRITE(" = 1; "); INV_A1;
    WRITE(" < i7_max_objects; "); INV_A1;
    WRITE("++) ");
    if (in_flag == FALSE) {
        WRITE("if (i7_ofclass("); INV_A1; WRITE(", "); INV_A2; WRITE(")) ");
    }
    WRITE("if (");
    INV_A3;
    WRITE(") {\n"); INDENT; INV_A4;
    OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.10. Generate primitive for objectloopx1.10 =

    WRITE("for (i7val "); INV_A1;
    WRITE(" = 1; "); INV_A1;
    WRITE(" < i7_max_objects; "); INV_A1;
    WRITE("++) ");
    WRITE("if (i7_ofclass("); INV_A1; WRITE(", "); INV_A2; WRITE(")) ");
    WRITE(" {\n"); INDENT; INV_A3;
    OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.11. Generate primitive for loop1.11 =

    WRITE("{\n"); INDENT; INV_A1; OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.12. Generate primitive for switch1.12 =

    WRITE("switch ("); INV_A1;
    WRITE(") {\n"); INDENT; INV_A2; OUTDENT; WRITE("}\n");
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.13. Generate primitive for case1.13 =

    CProgramControl::caser(gen,  InterTree::first_child(P));
    INDENT; INV_A2; WRITE(";\n"); WRITE("break;\n"); OUTDENT;
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§1.14. Generate primitive for default1.14 =

    WRITE("default:\n"); INDENT; INV_A1; WRITE(";\n"); WRITE("break;\n"); OUTDENT;
    suppress_terminal_semicolon = TRUE;

This code is used in §1.

§2.

void CProgramControl::caser(code_generation *gen, inter_tree_node *X) {
    if (X->W.data[ID_IFLD] == INV_IST) {
        if (X->W.data[METHOD_INV_IFLD] == INVOKED_PRIMITIVE) {
            inter_symbol *prim = Inter::Inv::invokee(X);
            inter_ti xbip = Primitives::to_bip(gen->from, prim);
            if (xbip == ALTERNATIVECASE_BIP) {
                CProgramControl::caser(gen, InterTree::first_child(X));
                CProgramControl::caser(gen, InterTree::second_child(X));
                return;
            }
        }
    }
    text_stream *OUT = CodeGen::current(gen);
    WRITE("case ");
    CodeGen::FC::frame(gen, X);
    WRITE(": ");
}