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ir_sccp.c
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/*
* IR - Lightweight JIT Compilation Framework
* (SCCP - Sparse Conditional Constant Propagation)
* Copyright (C) 2022 Zend by Perforce.
* Authors: Dmitry Stogov <[email protected]>
*
* The SCCP algorithm is based on M. N. Wegman and F. K. Zadeck publication
* See: M. N. Wegman and F. K. Zadeck. "Constant propagation with conditional branches"
* ACM Transactions on Programming Languages and Systems, 13(2):181-210, April 1991
*/
#include "ir.h"
#include "ir_private.h"
#define IR_COMBO_COPY_PROPAGATION 1
#define IR_TOP IR_UNUSED
#define IR_BOTTOM IR_LAST_OP
#define IR_MAKE_TOP(ref) do {IR_ASSERT(ref > 0); _values[ref].optx = IR_TOP;} while (0)
#define IR_MAKE_BOTTOM(ref) do {IR_ASSERT(ref > 0); _values[ref].optx = IR_BOTTOM;} while (0)
#define IR_IS_TOP(ref) (ref >= 0 && _values[ref].op == IR_TOP)
#define IR_IS_BOTTOM(ref) (ref >= 0 && _values[ref].op == IR_BOTTOM)
#define IR_IS_REACHABLE(ref) _ir_is_reachable_ctrl(ctx, _values, ref)
#define IR_IS_CONST(ref) (IR_IS_CONST_REF(ref) || IR_IS_CONST_OP(_values[ref].op))
IR_ALWAYS_INLINE bool _ir_is_reachable_ctrl(ir_ctx *ctx, ir_insn *_values, ir_ref ref)
{
IR_ASSERT(!IR_IS_CONST_REF(ref));
IR_ASSERT(ir_op_flags[ctx->ir_base[ref].op] & IR_OP_FLAG_CONTROL);
return _values[ref].op != IR_TOP; /* BOTTOM, IF or MERGE */
}
IR_ALWAYS_INLINE void ir_sccp_add_uses(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref)
{
ir_use_list *use_list;
ir_ref n, *p, use;
IR_ASSERT(!IR_IS_CONST_REF(ref));
use_list = &ctx->use_lists[ref];
n = use_list->count;
for (p = &ctx->use_edges[use_list->refs]; n > 0; p++, n--) {
use = *p;
if (_values[use].op != IR_BOTTOM) {
ir_bitqueue_add(worklist, use);
}
}
}
IR_ALWAYS_INLINE void ir_sccp_add_input(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref)
{
IR_ASSERT(!IR_IS_CONST_REF(ref));
IR_ASSERT(_values[ref].op == IR_TOP);
/* do backward propagaton only once */
if (!_values[ref].op1) {
_values[ref].op1 = 1;
ir_bitqueue_add(worklist, ref);
}
}
#if IR_COMBO_COPY_PROPAGATION
IR_ALWAYS_INLINE ir_ref ir_sccp_identity(ir_ctx *ctx, ir_insn *_values, ir_ref a)
{
if (a > 0 && _values[a].op == IR_COPY) {
do {
a = _values[a].op1;
IR_ASSERT(a > 0);
} while (_values[a].op == IR_COPY);
IR_ASSERT(_values[a].op == IR_BOTTOM);
}
return a;
}
#if 0
static void CHECK_LIST(ir_insn *_values, ir_ref ref)
{
ir_ref member = _values[ref].op2;
while (member != ref) {
IR_ASSERT(_values[_values[member].op2].op3 == member);
member = _values[member].op2;
}
IR_ASSERT(_values[_values[ref].op2].op3 == ref);
}
#else
# define CHECK_LIST(_values, ref)
#endif
static void ir_sccp_add_identity(ir_ctx *ctx, ir_insn *_values, ir_ref src, ir_ref dst)
{
IR_ASSERT(dst > 0 && _values[dst].op != IR_BOTTOM && _values[dst].op != IR_COPY);
IR_ASSERT((src > 0 && (_values[src].op == IR_BOTTOM || _values[src].op == IR_COPY)));
IR_ASSERT(ir_sccp_identity(ctx, _values, src) != dst);
_values[dst].optx = IR_COPY;
_values[dst].op1 = src;
if (_values[src].op == IR_BOTTOM) {
/* initialize empty double-linked list */
if (_values[src].op1 != src) {
_values[src].op1 = src;
_values[src].op2 = src;
_values[src].op3 = src;
}
} else {
src = ir_sccp_identity(ctx, _values, src);
}
/* insert into circular double-linked list */
ir_ref prev = _values[src].op3;
_values[dst].op2 = src;
_values[dst].op3 = prev;
_values[src].op3 = dst;
_values[prev].op2 = dst;
CHECK_LIST(_values, dst);
}
static void ir_sccp_split_partition(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref)
{
ir_ref member, head, tail, next, prev;
CHECK_LIST(_values, ref);
IR_MAKE_BOTTOM(ref);
_values[ref].op1 = ref;
member = _values[ref].op2;
head = tail = IR_UNUSED;
while (member != ref) {
if (_values[member].op != IR_BOTTOM) {
ir_bitqueue_add(worklist, member);
}
ir_sccp_add_uses(ctx, _values, worklist, member);
next = _values[member].op2;
if (ir_sccp_identity(ctx, _values, member) == ref) {
/* remove "member" from the old circular double-linked list */
prev = _values[member].op3;
_values[prev].op2 = next;
_values[next].op3 = prev;
/* insert "member" into the new double-linked list */
if (!head) {
head = tail = member;
} else {
_values[tail].op2 = member;
_values[member].op3 = tail;
tail = member;
}
}
member = next;
}
/* remove "ref" from the old circular double-linked list */
next = _values[ref].op2;
prev = _values[ref].op3;
_values[prev].op2 = next;
_values[next].op3 = prev;
CHECK_LIST(_values, next);
/* close the new circle */
if (head) {
_values[ref].op2 = head;
_values[ref].op3 = tail;
_values[tail].op2 = ref;
_values[head].op3 = ref;
} else {
_values[ref].op2 = ref;
_values[ref].op3 = ref;
}
CHECK_LIST(_values, ref);
}
IR_ALWAYS_INLINE void ir_sccp_make_bottom_ex(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref)
{
if (_values[ref].op == IR_COPY) {
ir_sccp_split_partition(ctx, _values, worklist, ref);
} else {
IR_MAKE_BOTTOM(ref);
}
}
# define IR_MAKE_BOTTOM_EX(ref) ir_sccp_make_bottom_ex(ctx, _values, worklist, ref)
#else
# define ir_sccp_identity(_ctx, _values, ref) (ref)
# define IR_MAKE_BOTTOM_EX(ref) IR_MAKE_BOTTOM(ref)
#endif
IR_ALWAYS_INLINE bool ir_sccp_meet_const(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref, ir_insn *val_insn)
{
IR_ASSERT(IR_IS_CONST_OP(val_insn->op) || IR_IS_SYM_CONST(val_insn->op));
if (_values[ref].op == IR_TOP) {
/* TOP meet NEW_CONST => NEW_CONST */
_values[ref].optx = val_insn->opt;
_values[ref].val.u64 = val_insn->val.u64;
return 1;
} else if (_values[ref].opt == val_insn->opt) {
/* OLD_CONST meet NEW_CONST => (OLD_CONST == NEW_CONST) ? OLD_CONST : BOTTOM */
if (_values[ref].val.u64 == val_insn->val.u64) {
return 0;
}
}
IR_MAKE_BOTTOM_EX(ref);
return 1;
}
IR_ALWAYS_INLINE bool ir_sccp_meet(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref, ir_ref val)
{
ir_ref val_identity = ir_sccp_identity(ctx, _values, val);
ir_insn *val_insn;
if (IR_IS_CONST_REF(val_identity)) {
val_insn = &ctx->ir_base[val_identity];
} else {
val_insn = &_values[val_identity];
if (!IR_IS_CONST_OP(val_insn->op) && !IR_IS_SYM_CONST(val_insn->op)) {
#if IR_COMBO_COPY_PROPAGATION
if (_values[ref].op == IR_COPY) {
/* COPY(OLD_VAL) meet COPY(NEW_VAL) =>
* (IDENTITY(OLD_VAL) == IDENTITY(NEW_VAL) ? COPY(OLD_VAL) ? BOTTOM */
if (ir_sccp_identity(ctx, _values, ref) == val_identity) {
return 0; /* not changed */
}
ir_sccp_split_partition(ctx, _values, worklist, ref);
return 1;
} else {
IR_ASSERT(_values[ref].op != IR_BOTTOM);
/* TOP meet COPY(NEW_VAL) -> COPY(NEW_VAL) */
/* OLD_CONST meet COPY(NEW_VAL) -> COPY(NEW_VAL) */
ir_sccp_add_identity(ctx, _values, val, ref);
return 1;
}
#endif
IR_MAKE_BOTTOM(ref);
return 1;
}
}
return ir_sccp_meet_const(ctx, _values, worklist, ref, val_insn);
}
static ir_ref ir_sccp_fold(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref ref, ir_insn *insn)
{
ir_insn *op1_insn, *op2_insn, *op3_insn;
ir_ref op1, op2, op3, copy;
uint32_t opt = insn->opt;
op1 = ir_sccp_identity(ctx, _values, insn->op1);
op2 = ir_sccp_identity(ctx, _values, insn->op2);
op3 = ir_sccp_identity(ctx, _values, insn->op3);
restart:
op1_insn = (op1 > 0 && IR_IS_CONST_OP(_values[op1].op)) ? _values + op1 : ctx->ir_base + op1;
op2_insn = (op2 > 0 && IR_IS_CONST_OP(_values[op2].op)) ? _values + op2 : ctx->ir_base + op2;
op3_insn = (op3 > 0 && IR_IS_CONST_OP(_values[op3].op)) ? _values + op3 : ctx->ir_base + op3;
switch (ir_folding(ctx, opt, op1, op2, op3, op1_insn, op2_insn, op3_insn)) {
case IR_FOLD_DO_RESTART:
opt = ctx->fold_insn.optx;
op1 = ctx->fold_insn.op1;
op2 = ctx->fold_insn.op2;
op3 = ctx->fold_insn.op3;
goto restart;
case IR_FOLD_DO_CSE:
case IR_FOLD_DO_EMIT:
IR_MAKE_BOTTOM_EX(ref);
return 1;
case IR_FOLD_DO_COPY:
copy = ctx->fold_insn.op1;
return ir_sccp_meet(ctx, _values, worklist, ref, copy);
case IR_FOLD_DO_CONST:
return ir_sccp_meet_const(ctx, _values, worklist, ref, &ctx->fold_insn);
default:
IR_ASSERT(0);
return 0;
}
}
static bool ir_sccp_analyze_phi(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_ref i, ir_insn *insn)
{
ir_ref j, n, input, *merge_input, *p;
ir_insn *v, *new_const = NULL;
#if IR_COMBO_COPY_PROPAGATION
ir_ref new_copy = IR_UNUSED;
ir_ref new_copy_identity = IR_UNUSED;
ir_ref phi_identity = ir_sccp_identity(ctx, _values, i);
#endif
if (!IR_IS_REACHABLE(insn->op1)) {
return 0;
}
n = insn->inputs_count;
if (n > 3 && _values[i].op == IR_TOP) {
for (j = 0; j < (n>>2); j++) {
_values[i+j+1].optx = IR_BOTTOM; /* keep the tail of a long multislot instruction */
}
}
p = insn->ops + 2;
merge_input = ctx->ir_base[insn->op1].ops + 1;
for (; --n > 0; p++, merge_input++) {
IR_ASSERT(*merge_input > 0);
if (!IR_IS_REACHABLE(*merge_input)) {
continue;
}
input = *p;
if (IR_IS_CONST_REF(input)) {
v = &ctx->ir_base[input];
} else if (input == i) {
continue;
} else {
v = &_values[input];
if (v->op == IR_TOP) {
ir_sccp_add_input(ctx, _values, worklist, input);
continue;
#if IR_COMBO_COPY_PROPAGATION
} else if (v->op == IR_COPY) {
input = v->op1;
new_copy_identity = ir_sccp_identity(ctx, _values, input);
if (new_copy_identity == phi_identity) {
new_copy_identity = IR_UNUSED;
continue;
}
new_copy = input;
goto next;
#endif
} else if (v->op == IR_BOTTOM) {
#if IR_COMBO_COPY_PROPAGATION
if (input == phi_identity) {
continue;
}
new_copy = new_copy_identity = input;
goto next;
#else
goto make_bottom;
#endif
}
}
new_const = v;
goto next;
}
return 0;
next:
p++;
merge_input++;
/* for all live merge inputs */
for (; --n > 0; p++, merge_input++) {
IR_ASSERT(*merge_input > 0);
if (!IR_IS_REACHABLE(*merge_input)) {
continue;
}
input = *p;
if (IR_IS_CONST_REF(input)) {
#if IR_COMBO_COPY_PROPAGATION
if (new_copy) {
goto make_bottom;
}
#endif
v = &ctx->ir_base[input];
} else if (input == i) {
continue;
} else {
v = &_values[input];
if (v->op == IR_TOP) {
ir_sccp_add_input(ctx, _values, worklist, input);
continue;
#if IR_COMBO_COPY_PROPAGATION
} else if (v->op == IR_COPY) {
ir_ref identity = ir_sccp_identity(ctx, _values, v->op1);
if (identity == phi_identity || identity == new_copy_identity) {
continue;
}
goto make_bottom;
#endif
} else if (v->op == IR_BOTTOM) {
#if IR_COMBO_COPY_PROPAGATION
if (input == phi_identity || input == new_copy_identity) {
continue;
}
#endif
goto make_bottom;
}
}
if (!new_const || new_const->opt != v->opt || new_const->val.u64 != v->val.u64) {
goto make_bottom;
}
}
#if IR_COMBO_COPY_PROPAGATION
if (new_copy) {
return ir_sccp_meet(ctx, _values, worklist, i, new_copy);
}
#endif
return ir_sccp_meet_const(ctx, _values, worklist, i, new_const);
make_bottom:
IR_MAKE_BOTTOM_EX(i);
return 1;
}
static bool ir_is_dead_load_ex(ir_ctx *ctx, ir_ref ref, uint32_t flags, ir_insn *insn)
{
if ((flags & (IR_OP_FLAG_MEM|IR_OP_FLAG_MEM_MASK)) == (IR_OP_FLAG_MEM|IR_OP_FLAG_MEM_LOAD)) {
return ctx->use_lists[ref].count == 1;
} else if (insn->op == IR_ALLOCA || insn->op == IR_BLOCK_BEGIN) {
return ctx->use_lists[ref].count == 1;
}
return 0;
}
static bool ir_is_dead_load(ir_ctx *ctx, ir_ref ref)
{
if (ctx->use_lists[ref].count == 1) {
uint32_t flags = ir_op_flags[ctx->ir_base[ref].op];
if ((flags & (IR_OP_FLAG_MEM|IR_OP_FLAG_MEM_MASK)) == (IR_OP_FLAG_MEM|IR_OP_FLAG_MEM_LOAD)) {
return 1;
} else if (ctx->ir_base[ref].op == IR_ALLOCA) {
return 1;
}
}
return 0;
}
static bool ir_is_dead(ir_ctx *ctx, ir_ref ref)
{
if (ctx->use_lists[ref].count == 0) {
return IR_IS_FOLDABLE_OP(ctx->ir_base[ref].op);
} else {
return ir_is_dead_load(ctx, ref);
}
return 0;
}
static bool ir_sccp_is_true(ir_ctx *ctx, ir_insn *_values, ir_ref a)
{
ir_insn *v = IR_IS_CONST_REF(a) ? &ctx->ir_base[a] : &_values[a];
return ir_const_is_true(v);
}
static bool ir_sccp_is_equal(ir_ctx *ctx, ir_insn *_values, ir_ref a, ir_ref b)
{
ir_insn *v1 = IR_IS_CONST_REF(a) ? &ctx->ir_base[a] : &_values[a];
ir_insn *v2 = IR_IS_CONST_REF(b) ? &ctx->ir_base[b] : &_values[b];
IR_ASSERT(!IR_IS_SYM_CONST(v1->op));
IR_ASSERT(!IR_IS_SYM_CONST(v2->op));
return v1->val.u64 == v2->val.u64;
}
#ifdef IR_SCCP_TRACE
static void ir_sccp_trace_val(ir_ctx *ctx, ir_insn *_values, ir_ref i)
{
if (IR_IS_BOTTOM(i)) {
fprintf(stderr, "BOTTOM");
} else if (IR_IS_CONST_OP(_values[i].op) || IR_IS_SYM_CONST(_values[i].op)) {
fprintf(stderr, "CONST(");
ir_print_const(ctx, &_values[i], stderr, true);
fprintf(stderr, ")");
#if IR_COMBO_COPY_PROPAGATION
} else if (_values[i].op == IR_COPY) {
fprintf(stderr, "COPY(%d)", _values[i].op1);
#endif
} else if (IR_IS_TOP(i)) {
fprintf(stderr, "TOP");
} else if (_values[i].op == IR_IF) {
fprintf(stderr, "IF(%d)", _values[i].op1);
} else if (_values[i].op == IR_MERGE) {
fprintf(stderr, "MERGE(%d)", _values[i].op1);
} else {
fprintf(stderr, "%d", _values[i].op);
}
}
static void ir_sccp_trace_start(ir_ctx *ctx, ir_insn *_values, ir_ref i)
{
fprintf(stderr, "%d. ", i);
ir_sccp_trace_val(ctx, _values, i);
}
static void ir_sccp_trace_end(ir_ctx *ctx, ir_insn *_values, ir_ref i)
{
fprintf(stderr, " -> ");
ir_sccp_trace_val(ctx, _values, i);
fprintf(stderr, "\n");
}
#else
# define ir_sccp_trace_start(c, v, i)
# define ir_sccp_trace_end(c, v, i)
#endif
static IR_NEVER_INLINE void ir_sccp_analyze(ir_ctx *ctx, ir_insn *_values, ir_bitqueue *worklist, ir_bitqueue *iter_worklist)
{
ir_ref i, j, n, *p, use;
ir_use_list *use_list;
ir_insn *insn, *use_insn;
uint32_t flags;
/* A bit modified SCCP algorithm of M. N. Wegman and F. K. Zadeck */
worklist->pos = 0;
ir_bitset_incl(worklist->set, 1);
for (; (i = ir_bitqueue_pop(worklist)) >= 0; ir_sccp_trace_end(ctx, _values, i)) {
IR_ASSERT(_values[i].op != IR_BOTTOM);
ir_sccp_trace_start(ctx, _values, i);
insn = &ctx->ir_base[i];
flags = ir_op_flags[insn->op];
if (flags & IR_OP_FLAG_DATA) {
if (ctx->use_lists[i].count == 0) {
/* dead code */
continue;
} else if (insn->op == IR_PHI) {
if (!ir_sccp_analyze_phi(ctx, _values, worklist, i, insn)) {
continue;
}
} else if (EXPECTED(IR_IS_FOLDABLE_OP(insn->op))) {
bool may_benefit = 0;
bool has_top = 0;
if (_values[i].op != IR_TOP) {
may_benefit = 1;
}
IR_ASSERT(!IR_OP_HAS_VAR_INPUTS(flags));
n = IR_INPUT_EDGES_COUNT(flags);
for (p = insn->ops + 1; n > 0; p++, n--) {
ir_ref input = *p;
if (input > 0) {
if (_values[input].op == IR_TOP) {
has_top = 1;
ir_sccp_add_input(ctx, _values, worklist, input);
} else if (_values[input].op != IR_BOTTOM) {
/* Perform folding only if some of direct inputs
* is going to be replaced by a constant or copy.
* This approach may miss some folding optimizations
* dependent on indirect inputs. e.g. reassociation.
*/
may_benefit = 1;
}
}
}
if (has_top) {
continue;
}
if (!may_benefit) {
IR_MAKE_BOTTOM_EX(i);
if (insn->op == IR_FP2FP || insn->op == IR_FP2INT || insn->op == IR_TRUNC) {
ir_bitqueue_add(iter_worklist, i);
}
} else if (!ir_sccp_fold(ctx, _values, worklist, i, insn)) {
/* not changed */
continue;
} else if (_values[i].op == IR_BOTTOM) {
insn = &ctx->ir_base[i];
if (insn->op == IR_FP2FP || insn->op == IR_FP2INT || insn->op == IR_TRUNC) {
ir_bitqueue_add(iter_worklist, i);
}
}
} else {
IR_MAKE_BOTTOM_EX(i);
}
} else if (flags & IR_OP_FLAG_BB_START) {
if (insn->op == IR_MERGE || insn->op == IR_LOOP_BEGIN || insn->op == IR_BEGIN) {
ir_bitqueue_add(iter_worklist, i);
}
if (insn->op == IR_MERGE || insn->op == IR_LOOP_BEGIN) {
ir_ref unfeasible_inputs = 0;
n = insn->inputs_count;
if (n > 3 && _values[i].op == IR_TOP) {
for (j = 0; j < (n>>2); j++) {
_values[i+j+1].optx = IR_BOTTOM; /* keep the tail of a long multislot instruction */
}
}
for (p = insn->ops + 1; n > 0; p++, n--) {
ir_ref input = *p;
IR_ASSERT(input > 0);
if (!IR_IS_REACHABLE(input)) {
unfeasible_inputs++;
}
}
if (unfeasible_inputs == 0) {
IR_MAKE_BOTTOM(i);
} else if (_values[i].op != IR_MERGE || _values[i].op1 != unfeasible_inputs) {
_values[i].optx = IR_MERGE;
_values[i].op1 = unfeasible_inputs;
} else {
continue;
}
if (ctx->flags2 & IR_MEM2SSA_VARS) {
/* MEM2SSA puts new PHI at the bottom, but we like to process them now */
use_list = &ctx->use_lists[i];
n = use_list->count;
for (p = &ctx->use_edges[use_list->refs]; n > 0; p++, n--) {
use = *p;
if (_values[use].op != IR_BOTTOM) {
if (ctx->ir_base[use].op == IR_PHI) {
ir_bitqueue_del(worklist, use);
if (ctx->use_lists[use].count != 0) {
if (ir_sccp_analyze_phi(ctx, _values, worklist, use, &ctx->ir_base[use])) {
ir_sccp_add_uses(ctx, _values, worklist, use);
}
}
} else {
ir_bitqueue_add(worklist, use);
}
}
}
continue;
}
} else {
IR_ASSERT(insn->op == IR_START || IR_IS_REACHABLE(insn->op1));
IR_MAKE_BOTTOM(i);
}
} else {
IR_ASSERT(insn->op1 > 0);
if (!IR_IS_REACHABLE(insn->op1)) {
/* control inpt is not feasible */
continue;
}
if (insn->op == IR_IF) {
if (IR_IS_TOP(insn->op2)) {
ir_sccp_add_input(ctx, _values, worklist, insn->op2);
continue;
}
if (IR_IS_CONST(insn->op2)) {
bool b = ir_sccp_is_true(ctx, _values, insn->op2);
use_list = &ctx->use_lists[i];
IR_ASSERT(use_list->count == 2);
p = &ctx->use_edges[use_list->refs];
use = *p;
use_insn = &ctx->ir_base[use];
IR_ASSERT(use_insn->op == IR_IF_TRUE || use_insn->op == IR_IF_FALSE);
if ((use_insn->op == IR_IF_TRUE) != b) {
use = *(p+1);
IR_ASSERT(ctx->ir_base[use].op == IR_IF_TRUE || ctx->ir_base[use].op == IR_IF_FALSE);
}
if (_values[i].op == IR_TOP) {
_values[i].optx = IR_IF;
_values[i].op1 = use;
ir_bitqueue_add(worklist, use);
continue;
} else if (_values[i].op == IR_IF && _values[i].op1 == use) {
continue;
}
}
IR_MAKE_BOTTOM(i);
ir_bitqueue_add(iter_worklist, i);
} else if (insn->op == IR_SWITCH) {
if (IR_IS_TOP(insn->op2)) {
ir_sccp_add_input(ctx, _values, worklist, insn->op2);
continue;
}
if (IR_IS_CONST(insn->op2)) {
ir_ref use_case = IR_UNUSED;
use_list = &ctx->use_lists[i];
n = use_list->count;
for (p = &ctx->use_edges[use_list->refs]; n > 0; p++, n--) {
use = *p;
IR_ASSERT(use > 0);
use_insn = &ctx->ir_base[use];
if (use_insn->op == IR_CASE_VAL) {
if (ir_sccp_is_equal(ctx, _values, insn->op2, use_insn->op2)) {
use_case = use;
break;
}
} else if (use_insn->op == IR_CASE_DEFAULT) {
use_case = use;
}
}
if (use_case) {
use_insn = &ctx->ir_base[use_case];
if (_values[i].op == IR_TOP) {
_values[i].optx = IR_IF;
_values[i].op1 = use_case;
ir_bitqueue_add(worklist, use_case);
continue;
} else if (_values[i].op == IR_IF || _values[i].op1 == use_case) {
continue;
}
}
}
IR_MAKE_BOTTOM(i);
} else if (ir_is_dead_load_ex(ctx, i, flags, insn)) {
/* schedule dead load elimination */
ir_bitqueue_add(iter_worklist, i);
IR_MAKE_BOTTOM(i);
} else {
if (_values[i].op == IR_TOP) {
bool has_top = 0;
/* control, call, load and store instructions may have unprocessed inputs */
n = IR_INPUT_EDGES_COUNT(flags);
if (IR_OP_HAS_VAR_INPUTS(flags) && (n = insn->inputs_count) > 3) {
for (j = 0; j < (n>>2); j++) {
_values[i+j+1].optx = IR_BOTTOM; /* keep the tail of a long multislot instruction */
}
for (j = 2, p = insn->ops + j; j <= n; j++, p++) {
IR_ASSERT(IR_OPND_KIND(flags, j) == IR_OPND_DATA);
use = *p;
if (use > 0 && _values[use].op == IR_TOP) {
has_top = 1;
ir_sccp_add_input(ctx, _values, worklist, use);
}
}
} else if (n >= 2) {
IR_ASSERT(IR_OPND_KIND(flags, 2) == IR_OPND_DATA);
use = insn->op2;
if (use > 0 && _values[use].op == IR_TOP) {
has_top = 1;
ir_sccp_add_input(ctx, _values, worklist, use);
}
if (n > 2) {
IR_ASSERT(n == 3);
IR_ASSERT(IR_OPND_KIND(flags, 3) == IR_OPND_DATA);
use = insn->op3;
if (use > 0 && _values[use].op == IR_TOP) {
has_top = 1;
ir_sccp_add_input(ctx, _values, worklist, use);
}
}
}
if (has_top && !(flags & IR_OP_FLAG_BB_END)) {
use = ir_next_control(ctx, i);
if (_values[use].op == IR_TOP) {
has_top = 1;
/* do forward control propagaton only once */
if (!_values[use].op1) {
_values[use].op1 = 1;
ir_bitqueue_add(worklist, use);
}
}
continue;
}
}
IR_MAKE_BOTTOM(i);
}
}
ir_sccp_add_uses(ctx, _values, worklist, i);
}
#ifdef IR_DEBUG
if (ctx->flags & IR_DEBUG_SCCP) {
for (i = 1; i < ctx->insns_count; i++) {
if (IR_IS_CONST_OP(_values[i].op) || IR_IS_SYM_CONST(_values[i].op)) {
fprintf(stderr, "%d. CONST(", i);
ir_print_const(ctx, &_values[i], stderr, true);
fprintf(stderr, ")\n");
#if IR_COMBO_COPY_PROPAGATION
} else if (_values[i].op == IR_COPY) {
fprintf(stderr, "%d. COPY(%d)\n", i, _values[i].op1);
#endif
} else if (IR_IS_TOP(i)) {
fprintf(stderr, "%d. TOP\n", i);
} else if (_values[i].op == IR_IF) {
fprintf(stderr, "%d. IF(%d)\n", i, _values[i].op1);
} else if (_values[i].op == IR_MERGE) {
fprintf(stderr, "%d. MERGE(%d)\n", i, _values[i].op1);
} else if (!IR_IS_BOTTOM(i)) {
fprintf(stderr, "%d. %d\n", i, _values[i].op);
}
}
}
#endif
}
/**********************/
/* SCCP trasformation */
/**********************/
static void ir_sccp_make_nop(ir_ctx *ctx, ir_ref ref)
{
ir_ref j, n, *p;
ir_insn *insn;
CLEAR_USES(ref);
insn = &ctx->ir_base[ref];
n = insn->inputs_count;
insn->opt = IR_NOP; /* keep "inputs_count" */
for (j = 1, p = insn->ops + j; j <= n; j++, p++) {
*p = IR_UNUSED;
}
}
static void ir_sccp_remove_insn(ir_ctx *ctx, ir_insn *_values, ir_ref ref, ir_bitqueue *worklist)
{
ir_ref j, n, *p;
ir_insn *insn;
CLEAR_USES(ref);
insn = &ctx->ir_base[ref];
n = insn->inputs_count;
insn->opt = IR_NOP; /* keep "inputs_count" */
for (j = 1, p = insn->ops + j; j <= n; j++, p++) {
ir_ref input = *p;
*p = IR_UNUSED;
/* we may skip nodes that are going to be removed by SCCP (TOP, CONST and COPY) */
if (input > 0 && _values[input].op > IR_COPY) {
ir_use_list_remove_all(ctx, input, ref);
if (ir_is_dead(ctx, input)) {
/* schedule DCE */
ir_bitqueue_add(worklist, input);
}
}
}
}
static void ir_sccp_replace_insn(ir_ctx *ctx, ir_insn *_values, ir_ref ref, ir_ref new_ref, ir_bitqueue *worklist)
{
ir_ref j, n, *p, use, i;
ir_insn *insn;
ir_use_list *use_list;
IR_ASSERT(ref != new_ref);
insn = &ctx->ir_base[ref];
#if IR_COMBO_COPY_PROPAGATION
if ((ir_op_flags[insn->op] & IR_OP_FLAG_MEM) && IR_IS_REACHABLE(insn->op1)) {
/* remove from control list */
ir_ref prev = insn->op1;
ir_ref next = ir_next_control(ctx, ref);
ctx->ir_base[next].op1 = prev;
ir_use_list_remove_one(ctx, ref, next);
ir_use_list_replace_one(ctx, prev, ref, next);
insn->op1 = IR_UNUSED;
}
#endif
n = insn->inputs_count;
insn->opt = IR_NOP; /* keep "inputs_count" */
for (j = 1, p = insn->ops + 1; j <= n; j++, p++) {
ir_ref input = *p;
*p = IR_UNUSED;
/* we may skip nodes that are going to be removed by SCCP (TOP, CONST and COPY) */
if (input > 0 && _values[input].op > IR_COPY) {
ir_use_list_remove_all(ctx, input, ref);
if (ir_is_dead(ctx, input)) {
/* schedule DCE */
ir_bitqueue_add(worklist, input);
}
}
}
use_list = &ctx->use_lists[ref];
n = use_list->count;
p = &ctx->use_edges[use_list->refs];
if (new_ref <= 0) {
/* constant or IR_UNUSED */
for (; n; p++, n--) {
use = *p;
/* we may skip nodes that are going to be removed by SCCP (TOP, CONST and COPY) */
if (_values[use].op > IR_COPY) {
insn = &ctx->ir_base[use];
i = ir_insn_find_op(insn, ref);
if (!i) continue;
IR_ASSERT(i > 0);
ir_insn_set_op(insn, i, new_ref);
/* schedule folding */
ir_bitqueue_add(worklist, use);
}
}
} else {
for (j = 0; j < n; j++, p++) {
use = *p;
/* we may skip nodes that are going to be removed by SCCP (TOP, CONST and COPY) */
if (_values[use].op == IR_BOTTOM) {
insn = &ctx->ir_base[use];
i = ir_insn_find_op(insn, ref);
IR_ASSERT(i > 0);
ir_insn_set_op(insn, i, new_ref);
if (ir_use_list_add(ctx, new_ref, use)) {
/* restore after reallocation */
use_list = &ctx->use_lists[ref];
n = use_list->count;
p = &ctx->use_edges[use_list->refs + j];
}
/* schedule folding */
ir_bitqueue_add(worklist, use);
}
}
}
CLEAR_USES(ref);
}
static void ir_sccp_remove_if(ir_ctx *ctx, ir_insn *_values, ir_ref ref, ir_ref dst)
{
ir_ref next;
ir_insn *insn, *next_insn;
insn = &ctx->ir_base[ref];
if (ctx->use_lists[dst].count == 1) {
next = ctx->use_edges[ctx->use_lists[dst].refs];
next_insn = &ctx->ir_base[next];
/* remove IF and IF_TRUE/FALSE from double linked control list */
next_insn->op1 = insn->op1;
ir_use_list_replace_one(ctx, insn->op1, ref, next);
/* remove IF and IF_TRUE/FALSE instructions */
ir_sccp_make_nop(ctx, ref);
ir_sccp_make_nop(ctx, dst);
} else {
insn->op2 = IR_UNUSED;
insn->optx = IR_OPTX(IR_END, IR_VOID, 1);
next_insn = &ctx->ir_base[dst];
next_insn->op = IR_BEGIN;
}
}
static bool ir_sccp_remove_unfeasible_merge_inputs(ir_ctx *ctx, ir_ref ref, ir_insn *insn, ir_bitqueue *worklist)
{
ir_ref old_merge_inputs, new_merge_inputs, i, *p;
ir_use_list *use_list;
ir_bitset life_inputs;
ir_bitset_base_t holder = 0;
IR_ASSERT(insn->op == IR_MERGE || insn->op == IR_LOOP_BEGIN);
old_merge_inputs = insn->inputs_count;
new_merge_inputs = 0;
life_inputs = (old_merge_inputs < IR_BITSET_BITS) ? &holder : ir_bitset_malloc(old_merge_inputs + 1);
for (i = 1; i <= old_merge_inputs; i++) {
ir_ref input = ir_insn_op(insn, i);
if (input) {
new_merge_inputs++;
if (new_merge_inputs != i) {
ir_insn_set_op(insn, new_merge_inputs, input);
}
ir_bitset_incl(life_inputs, i);
}
}
if (new_merge_inputs == old_merge_inputs) {
/* All inputs are feasible */
if (life_inputs != &holder) {
ir_mem_free(life_inputs);
}
return 0;
}
for (i = new_merge_inputs + 1; i <= old_merge_inputs; i++) {
ir_insn_set_op(insn, i, IR_UNUSED);
}
if (new_merge_inputs <= 1) {
#if 0
if (new_merge_inputs == 1
&& insn->op == IR_LOOP_BEGIN
&& insn->op1 > ref) { // TODO: check dominance instead of order
/* dead loop */
ir_use_list_remove_one(ctx, insn->op1, ref);
insn->op1 = IR_UNUSED;
new_merge_inputs = 0;
}
#endif
insn->optx = IR_OPTX(IR_BEGIN, IR_VOID, 1);
ir_bitqueue_add(worklist, ref);
} else {
insn->inputs_count = new_merge_inputs;
}
/* Update PHIs */
use_list = &ctx->use_lists[ref];
if (use_list->count > 1) {
ir_ref use_count = 0;
ir_ref *q;
for (i = 0, p = q = &ctx->use_edges[use_list->refs]; i < use_list->count; p++, i++) {
ir_ref use = *p;
ir_insn *use_insn = &ctx->ir_base[use];
if (use_insn->op == IR_PHI) {
ir_ref j, k;
/* compress PHI */
for (j = k = 1; j <= old_merge_inputs; j++) {
ir_ref input = ir_insn_op(use_insn, j + 1);
if (ir_bitset_in(life_inputs, j)) {
IR_ASSERT(input);
if (k != j) {
ir_insn_set_op(use_insn, k + 1, input);
}
k++;
} else if (input > 0) {
ir_use_list_remove_one(ctx, input, use);
}
}
while (k <= old_merge_inputs) {