Fix function pointer assignment

src/defs.h

@@ -408,6 +408,7 @@ struct var {
     int loop_depth; /* Nesting depth if variable is in a loop */
     int use_count;  /* Number of times variable is used */
     bool space_is_allocated; /* whether space is allocated for this variable */
+    bool aggregate_storage_is_allocated;
 
     /* This flag is used to indicate to the compiler that the offset of
      * the variable is based on the top of the local stack.

src/parser.c

@@ -3321,10 +3321,15 @@ bool read_body_assignment(char *token,
         } else if (lex_peek(T_open_bracket, NULL)) {
             /* dereference lvalue into function address */
             rs1 = opstack_pop();
-            vd = require_var(parent);
-            gen_name_to(vd->var_name);
-            opstack_push(vd);
-            add_insn(parent, *bb, OP_read, vd, rs1, NULL, PTR_SIZE, NULL);
+
+            if (lvalue.is_reference) {
+                vd = require_var(parent);
+                gen_name_to(vd->var_name);
+                opstack_push(vd);
+                add_insn(parent, *bb, OP_read, vd, rs1, NULL, PTR_SIZE, NULL);
+            } else {
+                opstack_push(rs1);
+            }
 
             read_indirect_call(parent, bb);
             return true;
@@ -3455,6 +3460,16 @@ bool read_body_assignment(char *token,
             if (lvalue.is_func) {
                 rs2 = opstack_pop();
                 rs1 = opstack_pop();
+
+                if (!lvalue.is_reference) {
+                    var_t *addr =
+                        require_ref_var(parent, lvalue.type, lvalue.ptr_level);
+                    gen_name_to(addr->var_name);
+                    add_insn(parent, *bb, OP_address_of, addr, rs1, NULL, 0,
+                             NULL);
+                    rs1 = addr;
+                }
+
                 add_insn(parent, *bb, OP_write, NULL, rs1, rs2, PTR_SIZE, NULL);
             } else if (lvalue.is_reference) {
                 rs2 = opstack_pop();

src/reg-alloc.c

@@ -44,6 +44,81 @@ int align_size(int i)
     return i <= 4 ? 4 : (i + 3) & ~3;
 }
 
+bool aggregate_has_func_member_seen(type_t *type, type_t **seen, int seen_count)
+{
+    if (!type)
+        return false;
+
+    for (int i = 0; i < seen_count; i++)
+        if (seen[i] == type)
+            return false;
+
+    if (seen_count >= MAX_TYPES)
+        return false;
+    seen[seen_count++] = type;
+
+    if (type->base_type == TYPE_typedef && type->base_struct)
+        type = type->base_struct;
+
+    for (int i = 0; i < type->num_fields; i++) {
+        var_t *field = &type->fields[i];
+        if (field->is_func)
+            return true;
+
+        /* Pointer fields do not contain the pointed-to object. */
+        if (!field->ptr_level && field->type && !field->type->ptr_level &&
+            (field->type->base_type == TYPE_struct ||
+             field->type->base_type == TYPE_union ||
+             field->type->base_type == TYPE_typedef) &&
+            aggregate_has_func_member_seen(field->type, seen, seen_count))
+            return true;
+    }
+
+    return false;
+}
+
+bool aggregate_has_func_member(type_t *type)
+{
+    type_t *seen[MAX_TYPES];
+    return aggregate_has_func_member_seen(type, seen, 0);
+}
+
+bool var_is_func_param(func_t *func, var_t *var)
+{
+    if (!func || !var)
+        return false;
+
+    for (int i = 0; i < func->num_params; i++) {
+        var_t *param = &func->param_defs[i];
+        if (var == param || var->base == param ||
+            (var->var_name[0] && !strcmp(var->var_name, param->var_name)))
+            return true;
+        for (int j = 0; j < param->subscripts_idx; j++)
+            if (var == param->subscripts[j])
+                return true;
+    }
+
+    return false;
+}
+
+int func_param_index(func_t *func, var_t *var)
+{
+    if (!func || !var)
+        return -1;
+
+    for (int i = 0; i < func->num_params; i++) {
+        var_t *param = &func->param_defs[i];
+        if (var == param || var->base == param ||
+            (var->var_name[0] && !strcmp(var->var_name, param->var_name)))
+            return i;
+        for (int j = 0; j < param->subscripts_idx; j++)
+            if (var == param->subscripts[j])
+                return i;
+    }
+
+    return -1;
+}
+
 bool check_live_out(basic_block_t *bb, var_t *var)
 {
     for (int i = 0; i < bb->live_out.size; i++) {
@@ -709,6 +784,10 @@ void reg_alloc(void)
                     else
                         func->stack_size += align_size(sz);
 
+                    if (!insn->rd->is_global &&
+                        aggregate_has_func_member(insn->rd->type))
+                        insn->rd->aggregate_storage_is_allocated = true;
+
                     dest = prepare_dest(bb, insn->rd, -1, -1);
                     ir = bb_add_ph2_ir(bb, OP_address_of);
                     ir->src0 = src0;
@@ -747,6 +826,91 @@ void reg_alloc(void)
                     insn->rs1->address_taken = true;
                     insn->rs1->is_const = false;
 
+                    /* OP_allocat reserves a word at offset for spilling the
+                     * address of a local function-pointer aggregate, followed
+                     * by its backing storage. Address-of must target that
+                     * backing storage, never the spill slot: otherwise a
+                     * later register spill overwrites a function member.
+                     *
+                     * Parameters do not have OP_allocat, so materialize their
+                     * incoming value in the same layout before taking its
+                     * address.
+                     */
+                    if (!insn->rs1->is_global &&
+                        aggregate_has_func_member(insn->rs1->type)) {
+                        if (!insn->rs1->aggregate_storage_is_allocated) {
+                            int src = -1;
+                            bool is_param =
+                                var_is_func_param(func, insn->rs1) ||
+                                !insn->rs1->space_is_allocated;
+
+                            if (is_param) {
+                                /* Load the incoming value while its original
+                                 * parameter offset is still available. */
+                                int param_idx =
+                                    func_param_index(func, insn->rs1);
+                                if (param_idx >= 0 &&
+                                    param_idx < MAX_ARGS_IN_REG)
+                                    src = param_idx;
+                                else if (param_idx >= MAX_ARGS_IN_REG)
+                                    src = prepare_operand(bb, insn->rs1, -1);
+                                else {
+                                    for (int i = 0; i < REG_CNT; i++)
+                                        if (REGS[i].var &&
+                                            aggregate_has_func_member(
+                                                REGS[i].var->type)) {
+                                            src = i;
+                                            break;
+                                        }
+                                    if (src < 0)
+                                        src = 0;
+                                }
+                                /* Aggregate arguments are passed by address;
+                                 * copy src aggregate value, not that address.
+                                 */
+                                ir = bb_add_ph2_ir(bb, OP_read);
+                                ir->src0 = src;
+                                ir->src1 = insn->rs1->type->size;
+                                ir->dest = src;
+                            }
+
+                            insn->rs1->offset = func->stack_size;
+                            insn->rs1->space_is_allocated = true;
+                            insn->rs1->ofs_based_on_stack_top = false;
+                            func->stack_size += PTR_SIZE;
+                            if (insn->rs1->ptr_level)
+                                sz = PTR_SIZE;
+                            else
+                                sz = insn->rs1->type->size;
+                            if (insn->rs1->array_size)
+                                func->stack_size +=
+                                    align_size(insn->rs1->array_size * sz);
+                            else
+                                func->stack_size += align_size(sz);
+                            insn->rs1->aggregate_storage_is_allocated = true;
+
+                            if (src >= 0) {
+                                ir = bb_add_ph2_ir(bb, OP_store);
+                                ir->src0 = src;
+                                ir->src1 = insn->rs1->offset;
+                                ir = bb_add_ph2_ir(bb, OP_store);
+                                ir->src0 = src;
+                                ir->src1 = insn->rs1->offset + PTR_SIZE;
+                                vreg_clear_phys(insn->rs1);
+                                REGS[src].var = NULL;
+                                REGS[src].polluted = 0;
+                            }
+                        }
+
+                        dest = prepare_dest(bb, insn->rd, -1, -1);
+                        ir = bb_add_ph2_ir(bb, OP_address_of);
+                        ir->src0 = insn->rs1->offset + PTR_SIZE;
+                        ir->dest = dest;
+                        ir->ofs_based_on_stack_top =
+                            insn->rs1->ofs_based_on_stack_top;
+                        break;
+                    }
+
                     /* make sure variable is on stack */
                     if (!insn->rs1->space_is_allocated) {
                         insn->rs1->offset = bb->belong_to->stack_size;
@@ -912,6 +1076,9 @@ void reg_alloc(void)
                     is_pushing_args = false;
                     args = 0;
                     handle_abi = false;
+
+                    for (int i = 0; i < REG_CNT; i++)
+                        REGS[i].var = NULL;
                     break;
                 case OP_func_ret:
                     dest = prepare_dest(bb, insn->rd, -1, -1);

tests/driver.sh

@@ -1643,6 +1643,94 @@ int main() {
 }
 EOF
 
+# Local function pointer, direct struct member, and pointer-to-struct member.
+# The first path must use the pointer value directly; the latter two must load
+# the pointer from the member slot.
+try_ 6 << EOF
+typedef struct {
+    int (*fn)(int);
+} holder_t;
+
+int suc(int x) { return x + 1; }
+
+int main() {
+    int (*local)(int);
+    holder_t h;
+    holder_t *p = &h;
+
+    local = suc;
+    h.fn = suc;
+    p->fn = suc;
+
+    return local(1) + h.fn(1) + p->fn(1);
+}
+EOF
+
+# An indirect call with two arguments must not leave stale argument-register
+# mappings visible to a later one-argument call.
+try_ 155 << EOF
+typedef struct {
+    int (*add)(int, int);
+} pair_holder_t;
+
+int add(int a, int b) { return a + b; }
+int one(int x) { return x + 100; }
+int get_right() { return 20; }
+
+int main() {
+    pair_holder_t h;
+    int left = 10;
+    int right = get_right();
+    h.add = add;
+    return h.add(left, right) + one(5) + right;
+}
+EOF
+
+# A function-pointer-containing aggregate passed in a register must be copied
+# into local backing storage before taking its address.
+try_ 5 << EOF
+typedef struct {
+    int (*fn)(int);
+} holder_t;
+
+int suc(int x) { return x + 1; }
+
+int call(holder_t h) {
+    holder_t *p = &h;
+    return p->fn(4);
+}
+
+int main() {
+    holder_t h;
+    h.fn = suc;
+    return call(h);
+}
+EOF
+
+# Nested aggregates must also receive backing storage when addressed.
+try_ 5 << EOF
+typedef struct {
+    int (*fn)(int);
+} inner_t;
+
+typedef struct {
+    inner_t inner;
+} outer_t;
+
+int suc(int x) { return x + 1; }
+
+int call(outer_t o) {
+    outer_t *p = &o;
+    return p->inner.fn(4);
+}
+
+int main() {
+    outer_t o;
+    o.inner.fn = suc;
+    return call(o);
+}
+EOF
+
 # struct with multiple pointer declarations in same line
 try_ 42 << EOF
 typedef struct chunk {