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gencode.c
2547 lines (1996 loc) · 83 KB
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gencode.c
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/*
Code generator.
Visit each node, and generate instructions as appropriate.
See ast.h for an overview of the AST node types. For most
nodes/functions, one (and sometimes more) m1_regs are pushed onto
a stack (accessible through the compiler structure parameter),
that holds the type and number of the register that will hold
the result of the expression for which code was generated.
Example: a node representing a floating point number will load
the number in an N register, and push that register so that other
functions can access it (i.e., popping it off the stack).
This happens in gencode_number().
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <assert.h>
#include <string.h>
#include "gencode.h"
#include "ast.h"
#include "compiler.h"
#include "stack.h"
#include "symtab.h"
#include "decl.h"
#include "instr.h"
#include "ann.h"
#define OUT stdout
#define M1DEBUG 1
#ifdef M1DEBUG
#define debug(x) fprintf(stderr, x);
#else
#define debug(x)
#endif
/* See PDD32 for these constants. */
#define M0_REG_I0 12
#define M0_REG_N0 73
#define M0_REG_S0 134
#define M0_REG_P0 195
static unsigned gencode_expr(M1_compiler *comp, m1_expression *e);
static void gencode_block(M1_compiler *comp, m1_block *block);
static unsigned gencode_obj(M1_compiler *comp, m1_object *obj, m1_object **parent, unsigned *dimension, int is_target);
static const char type_chars[REG_TYPE_NUM] = {'i', 'n', 's', 'p'};
static const char reg_chars[REG_TYPE_NUM] = {'I', 'N', 'S', 'P'};
#define LABEL(label) mk_label(comp, label)
#define INS(opcode, format, ...) mk_instr(comp, opcode, format, ##__VA_ARGS__)
#define CHUNK(name) mk_chunk(comp, name)
static void
reset_reg(M1_compiler *comp) {
/* Set all fields in the registers table to 0. */
memset(comp->registers, 0, sizeof(char) * REG_NUM * REG_TYPE_NUM);
}
#define REG_UNUSED 0
#define REG_USED 1
#define REG_SYMBOL 2
static m1_reg
alloc_reg(M1_compiler *comp, m1_valuetype type) {
m1_reg r;
int i = 0;
/* look for first empty slot. */
while (i < REG_NUM && comp->registers[type][i] != REG_UNUSED) {
i++;
}
/* XXX Need to properly handle spilling when out of registers. */
if (i >= REG_NUM) {
fprintf(stderr, "Out of registers!! Resetting it, hoping for the best!\n");
memset(comp->registers[type], 0, sizeof(char) * REG_NUM);
}
/* set the newly allocated register to "used". */
comp->registers[type][i] = REG_USED;
/* return the register. */
r.no = i;
r.type = type;
return r;
}
/*
Throughout the code, we call free_reg() on registers that we think we
no longer need. Sometimes, these registers have been assigned to a symbol.
Symbols get to keep what they get. In order to prevent very difficult code,
just note that the register is used by a symbol by "freezing" it.
When free_reg() is called on it (after it's frozen), it won't be freed by
free_reg().
*/
static void
freeze_reg(M1_compiler *comp, m1_reg r) {
assert(comp != NULL);
assert(r.type < REG_TYPE_NUM);
assert(r.no < REG_NUM);
assert(r.no >= 0);
comp->registers[r.type][r.no] = REG_SYMBOL;
}
/*
Make register C<r> available again, unless it's assigned to a symbol.
In that case, the register is left alone.
*/
static void
free_reg(M1_compiler *comp, m1_reg r) {
/* if m1 was invoked with -r, then switch off free_reg(). */
if (comp->no_reg_opt)
return;
/* if it's not frozen, it may be freed. */
if (comp->registers[r.type][r.no] != REG_SYMBOL) {
// fprintf(stderr, "Unusing %d for good\n", r.no);
comp->registers[r.type][r.no] = REG_UNUSED;
}
/* XXX this is for debugging. */
/*
int i;
for (i = 0; i < REG_NUM; i++)
fprintf(stderr, "%d", i % 10);
fprintf(stderr, "\n");
for (i = 0; i < REG_NUM; i++) {
fprintf(stderr, "%d", comp->registers[r.type][i]);
}
fprintf(stderr, "\n\n");
*/
}
/*
Generate label identifiers.
*/
static int
gen_label(M1_compiler *comp) {
assert(comp != NULL);
return ++comp->label;
}
static void
gencode_number(M1_compiler *comp, m1_literal *lit) {
/*
deref Nx, CONSTS, <const_id>
*/
m1_reg reg, constindex;
assert(comp != NULL);
assert(lit != NULL);
assert(lit->type == VAL_FLOAT);
assert(lit->sym != NULL);
reg = alloc_reg(comp, VAL_FLOAT);
constindex = alloc_reg(comp, VAL_INT);
INS (M0_SET_IMM, "%I, %d, %d", constindex.no, 0, lit->sym->constindex);
INS (M0_DEREF, "%N, %d, %I", reg.no, CONSTS, constindex.no);
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", constindex.no, lit->sym->constindex);
fprintf(OUT, "\tderef\tN%d, CONSTS, I%d\n", reg.no, constindex.no);
free_reg(comp, constindex);
pushreg(comp->regstack, reg);
}
static void
gencode_char(M1_compiler *comp, m1_literal *lit) {
/*
deref Nx, CONSTS, <const_id>
*/
m1_reg reg;
assert(comp != NULL);
assert(lit != NULL);
assert(lit->type == VAL_INT);
assert(lit->sym != NULL);
reg = alloc_reg(comp, VAL_INT);
INS (M0_SET_IMM, "%I, %d, %d", reg.no, 0, lit->sym->constindex);
INS (M0_DEREF, "%I, %d, %I", reg.no, CONSTS, reg.no);
/* reuse the reg, first for the index, then for the result. */
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", reg.no, lit->sym->constindex);
fprintf(OUT, "\tderef\tI%d, CONSTS, I%d\n", reg.no, reg.no);
pushreg(comp->regstack, reg);
}
static void
gencode_int(M1_compiler *comp, m1_literal *lit) {
/*
If the value is smaller than 256*255 and > 0,
then generate set_imm, otherwise, load the constant
from the constants table.
deref Ix, CONSTS, <const_id>
or:
set_imm Ix, y, z
*/
m1_reg reg;
assert(comp != NULL);
assert(lit != NULL);
assert(lit->type == VAL_INT);
assert(lit->sym != NULL);
reg = alloc_reg(comp, VAL_INT);
/* If the value is small enough, load it with set_imm; otherwise, take it from the constants table.
set_imm X, Y, Z: set X to: 256 * Y + Z. All operands are 8 bit, so maximum value is 255.
*/
if (lit->sym->value.ival < (256 * 255) && lit->sym->value.ival >= 0) {
/* use set_imm X, N*256, remainder) */
int remainder = lit->sym->value.ival % 256;
int num256 = (lit->sym->value.ival - remainder) / 256;
INS (M0_SET_IMM, "%I, %d, %d", reg.no, num256, remainder);
fprintf(OUT, "\tset_imm\tI%d, %d, %d\n", reg.no, num256, remainder);
}
else { /* too big enough for set_imm, so load it from constants segment. */
/* XXX this will fail if constindex > 255. */
INS (M0_SET_IMM, "%I, %d, %d", reg.no, 0, lit->sym->constindex);
INS (M0_DEREF, "%I, %d, %d", reg.no, CONSTS, reg.no);
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", reg.no, lit->sym->constindex);
fprintf(OUT, "\tderef\tI%d, CONSTS, I%d\n", reg.no, reg.no);
}
pushreg(comp->regstack, reg);
}
static void
gencode_null(M1_compiler *comp) {
m1_reg reg;
reg = alloc_reg(comp, VAL_INT);
/* "null" is just 0, but then in a "pointer" context. */
INS (M0_SET_IMM, "%I, %d, %d", reg.no, 0, 0);
fprintf(OUT, "\tset_imm\tI%d, 0, 0\n", reg.no);
pushreg(comp->regstack, reg);
}
static void
gencode_bool(M1_compiler *comp, int boolval) {
/* Generate one of these:
set_imm Ix, 0, 1 # for true
set_imm Ix, 0, 0 # for false
*/
m1_reg reg = alloc_reg(comp, VAL_INT);
INS (M0_SET_IMM, "%I, %d, %d", reg.no, 0, boolval);
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", reg.no, boolval);
pushreg(comp->regstack, reg);
}
static void
gencode_string(M1_compiler *comp, m1_literal *lit) {
m1_reg stringreg,
constidxreg;
assert(comp != NULL);
assert(lit != NULL);
assert(lit->sym != NULL);
assert(lit->type == VAL_STRING);
stringreg = alloc_reg(comp, VAL_STRING);
constidxreg = alloc_reg(comp, VAL_INT);
INS (M0_SET_IMM, "%I, %d, %d", constidxreg.no, 0, lit->sym->constindex);
INS (M0_DEREF, "%S, %d, %I", stringreg.no, CONSTS, constidxreg.no);
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", constidxreg.no, lit->sym->constindex);
fprintf(OUT, "\tderef\tS%d, CONSTS, I%d\n", stringreg.no, constidxreg.no);
free_reg(comp, constidxreg);
pushreg(comp->regstack, stringreg);
}
/* Generate code for assignments. */
static void
gencode_assign(M1_compiler *comp, NOTNULL(m1_assignment *a)) {
m1_object *parent_dummy; /* pointer storage needed for code generation of LHS. */
unsigned lhs_reg_count; /* number of regs holding result of LHS (can be aggregate/indexed) */
unsigned rhs_reg_count; /* number of regs holding result of RHS (can be aggregate/indexed) */
unsigned dimension_dummy = 0;
assert(a != NULL);
/* Generate code for RHS and get number of registers that hold the result
Note that since the AST for an assignment was right-recursive, for a = b = c,
it looks like this:
=
/ \
a =
/ \
b c
Since RHS is evaluated first, code for b=c is generated first.
*/
rhs_reg_count = gencode_expr(comp, a->rhs);
/* Generate code for LHS and get number of registers that hold the result
Note the "1" argument; this is to indicate we want to generate code for LHS
as an l-value.
*/
lhs_reg_count = gencode_obj(comp, a->lhs, &parent_dummy, &dimension_dummy, 1);
if (rhs_reg_count == 2) { /* deref; ... = x[42] */
if (lhs_reg_count == 1) { /* lhs_reg_count + rhs_reg_count == 3, so pop 3 regs. */
/* XXX check whether this code ever gets executed! */
m1_reg target = popreg(comp->regstack);
m1_reg index = popreg(comp->regstack);
m1_reg parent = popreg(comp->regstack);
INS (M0_DEREF, "%R, %R, %R", target, parent, index);
fprintf(OUT, "\tderef\t%c%d, %c%d, %c%d\n", reg_chars[(int)target.type], target.no,
reg_chars[(int)parent.type], parent.no,
reg_chars[(int)index.type], index.no);
free_reg(comp, target);
free_reg(comp, index);
free_reg(comp, parent);
}
else {
assert(0); /* should never happen. */
}
}
else { /* must be set_ref or set */
if (lhs_reg_count == 1) { /* just a simple lvalue; a = b; */
m1_reg lhs = popreg(comp->regstack);
m1_reg rhs = popreg(comp->regstack);
INS (M0_SET, "%R, %R", lhs, rhs);
fprintf(OUT, "\tset \t%c%d, %c%d, x\n", reg_chars[(int)lhs.type], lhs.no,
reg_chars[(int)rhs.type], rhs.no);
pushreg(comp->regstack, lhs);
free_reg(comp, rhs); /* to free regs for constants; for symbols they should be frozen. */
}
else if (lhs_reg_count == 2) { /* complex lvalue; x[10] = 42 */
assert(rhs_reg_count == 1); /* lhs_reg_count+rhs_reg_count == 3, so pop 3 regs. */
m1_reg index = popreg(comp->regstack);
m1_reg parent = popreg(comp->regstack);
m1_reg rhs = popreg(comp->regstack);
INS (M0_SET_REF, "%R, %R, %R", parent, index, rhs);
fprintf(OUT, "\tset_ref\t%c%d, %c%d, %c%d\n", reg_chars[(int)parent.type], parent.no,
reg_chars[(int)index.type], index.no,
reg_chars[(int)rhs.type], rhs.no);
free_reg(comp, index);
free_reg(comp, parent);
/* make result available for next in "chain" of assignments, if any (e.g, a = b = c = 42;). */
pushreg(comp->regstack, rhs);
}
}
}
/*
Generate instructions for an m1_object node; this may be as simple as a single identifier
(e.g., "x"), or as complex as a combination of array access and struct member access
(e.g., x[1][2][3], x.y.z). The function returns the number of registers that are used
to refer to the object; this is either 1 (simple case) or 2 (array or struct). Though
an object can be of arbitrary complexity, this is always reduced to 2 registers
(possibly emitting instructions in this function; as soon as 3 registers are needed,
an instruction is emitted, and one register is removed. See the comments inside.)
The dimension parameter is also an OUT parameter, and is used in particular for arrays.
When handling x[1][2][3], and we're calculating the offset from the base address (x),
we need to know which dimension we're in (1, 2 or 3 in the example of x[1][2][3]).
The <parent> parameter always points to the last identifier; in case of x.y.z, when
handling y, <parent> points to x; when handling z, <parent> points to y.
The <dimension> parameter always counts the array dimension that we're handling. It is
ONLY needed for multi-dimensional arrays. In x[10][11][12], when handling [10],
<dimension> is 1, when handling [11], it's 2, when handling [12], it's 3.
In x[10].y[11].z[12], it's always 1, because the dimensions are separated; that is,
none of the arrays is multi-dimensional.
*/
static unsigned
gencode_obj(M1_compiler *comp, m1_object *obj, m1_object **parent, unsigned *dimension, int is_target)
{
unsigned numregs_pushed = 0;
assert(comp != NULL);
assert(comp->currentchunk != NULL);
assert(comp->currentsymtab != NULL);
/* visit this node's parent recursively, depth-first.
parent parameter will return a pointer to it so it can
be passed on when visiting the field. Note that this invocation
is recursive, so THIS function will be called again. Note also that
the tree was built upside down, so obj->parent is really its parent
in which the current node is a (link-node to a) field.
x.y.z looks like this:
OBJECT_MAIN
|
| OBJECT_FIELD
| |
| | OBJECT_FIELD
V V V
x y z
\ / /
OBJECT_LINK-----> L1 /
\ /
OBJECT_LINK-------> L2
^
|
ROOT
Node L2 is the root in this tree. Both L1 and L2 are of type OBJECT_LINK.
Node "x" is OBJECT_MAIN, whereas nodes "y" and "z" are OBJECT_FIELD.
First this function (gencode_obj) goes all the way down to x, sets the
OUT parameter "parent" to itself, then as the function returns, comes
back to L1, then visits y, passing on a pointer to node for "x" through
the parent parameter. Then, node y sets the parent OUT parameter to itself
(again, in this funciton gencode_obj), and then control goes up to L2,
visiting z, passing a pointer to node "y" through the parent parameter.
x[42] looks like this:
OBJECT_MAIN
|
| OBJECT_INDEX
| |
V V
x 42
\ /
\/
OBJECT_LINK-----> L1
^
|
ROOT
As an example of multi-dimensional arrays:
x[1][2][3] looks like this:
OBJECT_MAIN
| OBJECT_INDEX (3x)
| | | |
V V V V
x 1 2 3
\ / / /
OBJECT_LINK------> L1 / /
\ / /
OBJECT_LINK------> L2 /
\ /
OBJECT_LINK------> L3
^
|
ROOT
Case for l-values: (x[1][2] = ...)
==================================
When traversing the tree starting at ROOT (L3), we go down towards OBJECT_MAIN
first by following the nodes' <parent> links. From L3->L2->L1->x. Then the OUT
parameter <parent> is set to x, and the register containing x (say, I0) is
pushed onto the regstack. We go back to L1, as x's parent is NULL. Then
L1's field will be visited, which is [3]. We load [1] into a register, and push
it onto the regstack. Then we go back to L2. We visit its <field>, which is
[2]. We load [2] into a register and push that register onto the regstack.
The regstack now looks like (growing bottom-up) this:
| |
| I2 (2) | <--SP (stack pointer)
| I1 (1) |
| I0 (x) |
---------- <--SB (stack base)
Since set_ref and deref ops only use 2 operands for the target or source, respectively,
we need to combine 2 registers into 1. We'll combine I0 and I1, by adding I1 to I0.
Access to an array element x[1][2] in an array defined as "int x[4][3]" is laid out
as follows, marked with "XX" : (|--| is 1 integer)
x[0][0] x[1][2]
| x[1] |
| | |
V | V
V XX
|--|--|--| |--|--|--| |--|--|--| |--|--|--|
0 1 2 0 1 2 0 1 2 0 1 2 [3]
__________ __________ __________ __________
0 1 2 3 x[4]
Therefore, x[1] represents the base address of "x" + "1 X 3" (since each "element"
in the first dimension has length 3). Therefore, generate the following instruction:
set_imm I4, 0, 3 # length of each "element" in first dimension.
mult_i I1, I1, I4 # multiply [1] by 3
add_i I0, I0, I1 # x = x + 3.
For this, we can pop off the 3 register so far, and push back I0 and I2, resulting in:
| |
| I2 (4) | <---SP
| I0 (x+[3]) |
-------------- <---SB
For each additional dimension, do the same thing, whenever there are 3 registers
on the stack, reduce it to two.
Case for r-values: ( ... = x[1][2])
===================================
Same example, accessing x[1][2] in same array defined as x[4][3], as above.
Instead of "set_ref", we want to generate "deref".
I0 contains pointer to "x".
Load 1 and 2 in registers I1 and I2 respectively, so the stack looks like this:
| |
| I2 | # holds 2
| I1 | # holds 1
| I0 | # holds x
------
Since we want to "dereference" x with indices [1] and [2], storing the result in [3]
we want to write:
deref I3, I0, I1, I2
but since there are only 3 operands, I0 and I1 are combined into I0:
deref I3, I0, I2
For that to work, I0 and I1 need to be combined:
set_imm I4, 0, 3 # load size of elements in first dimension
mult_i I1, I1, I4 # multiply I1 by 3
add_i I0, I0, I1 # x = x + 3
and then the deref instruction.
*/
switch (obj->type) {
case OBJECT_LINK:
{
/* set OUT parameter to this node (that's currently visited, obj) */
*parent = obj;
/* count the number of regs pushed by the parent, which is 1. */
numregs_pushed += gencode_obj(comp, obj->parent, parent, dimension, is_target);
/* At this point, we're done visiting parents, so now visit the "fields".
In x.y.z, after returning from x, we're visiting y. After that, we'll visit z.
As we do this, keep track of how many registers were used to store the result.
*/
numregs_pushed += gencode_obj(comp, obj->obj.field, parent, dimension, is_target);
if (numregs_pushed == 3) {
/* if the field was an index. (a[b]) */
if (obj->obj.field->type == OBJECT_INDEX) {
m1_reg last = popreg(comp->regstack); /* latest added; store here for now. */
m1_reg field = popreg(comp->regstack); /* 2nd latest, this one needs to be removed. */
m1_reg parentreg = popreg(comp->regstack); /* x in x[2][3]. */
m1_reg size_reg = alloc_reg(comp, VAL_INT); /* to hold amount to add. */
m1_reg updated_parent = alloc_reg(comp, VAL_INT); /* need to copy base address from parent. */
/* 3 registers only the case when 2 dimensions are parsed, e.g., x[10][20].
Find the size of the first dimension, since that's the one that's
added to the parent's base address, i.e., adding 10 * sizeof(type).
Get a pointer to the m1_var node for the parent; this is accessible
through the <sym> field of the parent; m1_var and m1_symbol nodes
have pointers to each other.
*/
assert((*parent)->sym != NULL);
assert((*parent)->sym->var != NULL);
/* get pointer to AST node for parent's m1_var node. */
m1_var *parent_var = (*parent)->sym->var;
m1_dimension *current_dimension = parent_var->dims;
/* Now find right dimension. The number in dimension keeps track of
which dimension we're currently visiting. Dimensions are stored in a
linked list, so set the pointer <num_get_next> times to the dimension
node's next.
*/
{ /* local scope to limit num_get_text. */
unsigned num_get_next;
for (num_get_next = *dimension - 1; num_get_next != 0; num_get_next--) {
assert(current_dimension->next != NULL);
current_dimension = current_dimension->next;
}
}
/* Calculate the offset; load the number of elements in the current dimension,
and multiply by the index of this dimension. In other words, x[2] in the
array declared as x[4][5] means 2 * 4 is added to base address of x.
The added offset is indicated by the <---> line below:
<----------->
^
V
|-----|-----|-----|-----|
^ ^ ^ ^
x[0] x[1] x[2] x[3]
*/
INS (M0_SET_IMM, "%I, %d, %d", size_reg.no, 0, current_dimension->num_elems);
INS (M0_MULT_I, "%I, %I, %I", field.no, field.no, size_reg.no);
fprintf(OUT, "\tset_imm\tI%d, 0, %d\n", size_reg.no, current_dimension->num_elems);
fprintf(OUT, "\tmult_i\tI%d, I%d, I%d\n", field.no, field.no, size_reg.no);
/* Need to have the following instruction (set X, Y), otherwise it doesn't work. */
INS (M0_SET, "%I, %I", updated_parent.no, parentreg.no);
INS (M0_ADD_I, "%I, %I, %I", updated_parent.no, updated_parent.no, field.no);
fprintf(OUT, "\tset \tI%d, I%d, x\n", updated_parent.no, parentreg.no);
fprintf(OUT, "\tadd_i\tI%d, I%d, I%d\n", updated_parent.no, updated_parent.no, field.no);
pushreg(comp->regstack, updated_parent); /* push back address of "x+[2]" */
pushreg(comp->regstack, last); /* push back the latest added one. */
free_reg(comp, size_reg);
free_reg(comp, field);
free_reg(comp, parentreg);
/* we popped 3, and pushed 2, so effectively decrement by 1. */
--numregs_pushed;
}
else if (obj->obj.field->type == OBJECT_FIELD) {
/* field is a struct member access (a.b) */
m1_reg last = popreg(comp->regstack);
m1_reg offset = popreg(comp->regstack);
m1_reg parentreg = popreg(comp->regstack);
m1_reg target = alloc_reg(comp, VAL_INT);
INS (M0_DEREF, "%I, %I, %I", target.no, parentreg.no, offset.no);
fprintf(OUT, "\tderef\tI%d, I%d, I%d\n", target.no, parentreg.no, offset.no);
pushreg(comp->regstack, target);
pushreg(comp->regstack, last);
/* popped 3 regs; pushed 2, so decrement numregs_pushed. */
free_reg(comp, offset);
free_reg(comp, parentreg); /* root parent (x in x.y.z) won't be freed, but y in x.y.z would. */
--numregs_pushed;
}
}
break;
}
case OBJECT_MAIN:
{
m1_reg reg;
assert(obj->obj.field != NULL);
assert(obj->sym != NULL);
assert(obj->sym->typedecl != NULL);
/* if symbol has not register allocated yet, do it now. */
if (obj->sym->regno == NO_REG_ALLOCATED_YET) {
m1_reg r = alloc_reg(comp, obj->sym->typedecl->valtype);
obj->sym->regno = r.no;
freeze_reg(comp, r);
}
/* Decide what type of register to use; for arrays it's always INT
as pointers are stored as integers. */
if (obj->sym->num_elems > 1) { /* it's an array! store it in an int register. */
reg.type = VAL_INT;
}
else {
/* it's not an array; just get the root type (in string[10], that's string). */
assert(obj->sym->num_elems == 1);
reg.type = obj->sym->typedecl->valtype;
}
reg.no = obj->sym->regno;
freeze_reg(comp, reg);
/* return a pointer to this node by OUT parameter. */
*parent = obj;
pushreg(comp->regstack, reg);
++numregs_pushed; /* just pushed, count it. */
break;
}
case OBJECT_FIELD: /* example: b in a.b */
{
m1_reg fieldreg = alloc_reg(comp, VAL_INT);/* reg for storing offset of field. */
assert((*parent) != NULL);
assert((*parent)->sym != NULL);
assert((*parent)->sym->typedecl != NULL);
/* parent's symbol has a typedecl node, which holds the structdef (d.s), which has a symbol table. */
m1_symbol *fieldsym = sym_lookup_symbol(&(*parent)->sym->typedecl->d.s->sfields, obj->obj.name);
assert(fieldsym != NULL);
/* load the offset into a reg. and make it available through the regstack. */
INS (M0_SET_IMM, "%I, %d, %d", fieldreg.no, 0, fieldsym->offset);
fprintf(OUT, "\tset_imm I%d, 0, %d\n", fieldreg.no, fieldsym->offset);
/* make it available through the regstack */
pushreg(comp->regstack, fieldreg);
++numregs_pushed;
/* set parent OUT parameter to the current node. */
*parent = obj;
/* whenever there's a field, reset dimension;
e.g. in x[4].y[5], when handling [5], dimension should be 1 again,
not 2. Since the "chain" is broken by the field y in the middle,
dimension needs to be reset. (both x and y are single-dimension arrays).
*/
(*dimension) = 0;
break;
}
case OBJECT_DEREF: /* b in a->b */
{
fprintf(stderr, "a->b is not yet implemented\n");
assert(0);
break;
}
case OBJECT_INDEX: /* b in a[b] */
{
(*dimension)++; /* increment dimension whenever we handle an index. */
numregs_pushed += gencode_expr(comp, obj->obj.index);
break;
}
default:
fprintf(stderr, "unknown object type in gencode_obj()\n");
assert(0);
break;
}
/* return the number of registers that are pushed onto the stack in this function. */
return numregs_pushed;
}
static void
gencode_while(M1_compiler *comp, m1_whileexpr *w) {
/*
...
goto LTEST
LBLOCK
<block>
LTEST:
code for <cond>
goto_if <cond>, LBLOCK
...
*/
m1_reg reg;
int startlabel = gen_label(comp),
endlabel = gen_label(comp);
/* push break label onto stack so break statement knows where to go. */
push(comp->breakstack, endlabel);
push(comp->continuestack, startlabel);
INS (M0_GOTO, "%L", endlabel);
fprintf(OUT, "\tgoto L%d\n", endlabel);
LABEL (startlabel);
fprintf(OUT, "L%d:\n", startlabel);
gencode_expr(comp, w->block);
LABEL (endlabel);
fprintf(OUT, "L%d:\n", endlabel);
gencode_expr(comp, w->cond);
reg = popreg(comp->regstack);
INS (M0_GOTO_IF, "%L, %R", startlabel, reg);
fprintf(OUT, "\tgoto_if\tL%d, %c%d\n", startlabel, reg_chars[(int)reg.type], reg.no);
free_reg(comp, reg);
/* remove break and continue labels from stack. */
(void)pop(comp->breakstack);
(void)pop(comp->continuestack);
}
static void
gencode_dowhile(M1_compiler *comp, m1_whileexpr *w) {
/*
LSTART:
<code for block>
cond = <code for cond>
goto_if LSTART, cond
*/
m1_reg reg;
int startlabel = gen_label(comp);
int endlabel = gen_label(comp);
push(comp->breakstack, endlabel);
push(comp->continuestack, startlabel);
LABEL (startlabel);
fprintf(OUT, "L%d:\n", startlabel);
gencode_expr(comp, w->block);
gencode_expr(comp, w->cond);
reg = popreg(comp->regstack);
INS (M0_GOTO_IF, "%L, %R", startlabel, reg);
fprintf(OUT, "\tgoto_if\tL%d, %c%d\n", startlabel, reg_chars[(int)reg.type], reg.no);
LABEL (endlabel);
fprintf(OUT, "L%d:\n", endlabel);
free_reg(comp, reg);
(void)pop(comp->breakstack);
(void)pop(comp->continuestack);
}
static void
gencode_for(M1_compiler *comp, m1_forexpr *i) {
/*
<code for init>
LSTART:
<code for cond>
goto_if cond, LBLOCK
goto LEND
LBLOCK:
<code for block>
<code for step>
goto LSTART
LEND:
*/
int startlabel = gen_label(comp),
endlabel = gen_label(comp),
steplabel = gen_label(comp),
blocklabel = gen_label(comp); /* label where the block starts */
push(comp->breakstack, endlabel);
push(comp->continuestack, steplabel); /* XXX check if this is the right label. */
if (i->init)
gencode_expr(comp, i->init);
LABEL (startlabel);
fprintf(OUT, "L%d:\n", startlabel);
if (i->cond) {
m1_reg reg;
gencode_expr(comp, i->cond);
reg = popreg(comp->regstack);
INS (M0_GOTO_IF, "%L, %R", blocklabel, reg);
fprintf(OUT, "\tgoto_if L%d, %c%d\n", blocklabel, reg_chars[(int)reg.type], reg.no);
free_reg(comp, reg);
}
INS (M0_GOTO, "%L", endlabel);
fprintf(OUT, "\tgoto L%d\n", endlabel);
LABEL (blocklabel);
fprintf(OUT, "L%d:\n", blocklabel);
if (i->block)
gencode_expr(comp, i->block);
LABEL (steplabel);
fprintf(OUT, "L%d:\n", steplabel);
if (i->step)
gencode_expr(comp, i->step);
INS (M0_GOTO, "%L", startlabel);
fprintf(OUT, "\tgoto L%d\n", startlabel);
LABEL (endlabel);
fprintf(OUT, "L%d:\n", endlabel);
(void)pop(comp->breakstack);
(void)pop(comp->continuestack);
}
static void
gencode_if(M1_compiler *comp, m1_ifexpr *i) {
/*
result = <evaluate condition>
goto_if LIF, result
<code for elseblock>
goto LEND
LIF:
<code for ifblock>
LEND:
*/
m1_reg condreg;
int endlabel = gen_label(comp),
iflabel = gen_label(comp);
gencode_expr(comp, i->cond);
condreg = popreg(comp->regstack);
INS (M0_GOTO_IF, "%L, %R", iflabel, condreg);
fprintf(OUT, "\tgoto_if\tL%d, %c%d\n", iflabel, reg_chars[(int)condreg.type], condreg.no);
free_reg(comp, condreg);
/* else block */
if (i->elseblock) {
gencode_expr(comp, i->elseblock);
}
INS (M0_GOTO, "%L", endlabel);
fprintf(OUT, "\tgoto L%d\n", endlabel);
/* if block */
LABEL (iflabel);
fprintf(OUT, "L%d:\n", iflabel);
gencode_expr(comp, i->ifblock);
LABEL (endlabel);
fprintf(OUT, "L%d:\n", endlabel);
}
static void
gencode_deref(M1_compiler *comp, m1_object *o) {
unsigned dimension_dummy = 0;
/* XXX need equivalent of C's *obj operator. */
gencode_obj(comp, o, NULL, &dimension_dummy, 0);
}
static void
gencode_address(M1_compiler *comp, m1_object *o) {
unsigned dimension_dummy = 0;
/* XXX need equivalent of C's &obj operator. */
gencode_obj(comp, o, NULL, &dimension_dummy, 0);