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Code Issues 1 Releases Wiki Activity

Add passes to remove unused constants and closures.

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Dead code elimination and value numbering may remove
closures and constants from a function def - remove these from our
constant and defs buffers to avoid keeping phantom references and
bloating marshalled function size.
This commit is contained in:
Calvin Rose
2026-09-19 12:59:04 -05:00
parent 6e79ac9f62
commit 95bc5742e0
1 changed files with 118 additions and 1 deletions
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src/core/bytecode.c
+118 -1
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@@ -900,6 +900,120 @@ static void rewrite_symbolmap(JanetFuncDef *def, uint32_t *pc_map) {
def->symbolmap_length = smout;
}
/* Remove unused closure defs */
void janet_bytecode_remove_unused_closures(JanetFuncDef *def) {
if (def->defs_length < 1) return;
uint32_t *code = def->bytecode;
int32_t words = ((def->defs_length - 1) >> 5) + 1;
janet_assert(words > 0, "bad length");
uint32_t *bitset = array_allocate(sizeof(uint32_t), words);
memset(bitset, 0, words * sizeof(uint32_t));
for (int32_t pc = 0; pc < def->bytecode_length; pc++) {
uint32_t E = code[pc] >> 16;
switch (code[pc] & 0x7F) {
default:
continue;
case JOP_CLOSURE:
bs_set_bit(bitset, E);
continue;
}
}
/* Check if we need to compress closures */
int remap = 0;
for (int32_t i = 0; i < def->defs_length; i++) {
if (!bs_read_bit(bitset, i)) {
remap = 1;
break;
}
}
/* Remap closures */
if (remap) {
uint32_t *def_remaps = array_allocate(sizeof(uint32_t), def->defs_length);
int32_t j = 0;
for (int32_t i = 0; i < def->defs_length; i++) {
def_remaps[i] = j;
def->defs[j] = def->defs[i];
if (bs_read_bit(bitset, i)) {
j++;
}
}
def->defs_length = j;
for (int32_t pc = 0; pc < def->bytecode_length; pc++) {
uint32_t E = code[pc] >> 16;
switch (code[pc] & 0x7F) {
default:
continue;
case JOP_CLOSURE:
code[pc] = (code[pc] & 0xFFFF) | (def_remaps[E] << 16);
continue;
}
}
janet_free(def_remaps);
/* TODO - recalculate closure bitset and do more optimization */
}
janet_free(bitset);
}
/* Remove unused constants from the constant buffer */
void janet_bytecode_remove_unused_constants(JanetFuncDef *def) {
if (def->constants_length < 1) return;
uint32_t *code = def->bytecode;
int32_t words = ((def->constants_length - 1) >> 5) + 1;
janet_assert(words > 0, "bad length");
uint32_t *bitset = array_allocate(sizeof(uint32_t), words);
memset(bitset, 0, words * sizeof(uint32_t));
for (int32_t pc = 0; pc < def->bytecode_length; pc++) {
uint32_t E = code[pc] >> 16;
switch (code[pc] & 0x7F) {
default:
continue;
case JOP_LOAD_CONSTANT:
bs_set_bit(bitset, E);
continue;
}
}
/* Check if we need to compress constants */
int remap = 0;
for (int32_t i = 0; i < def->constants_length; i++) {
if (!bs_read_bit(bitset, i)) {
remap = 1;
break;
}
}
/* Remap constants */
if (remap) {
uint32_t *constant_remaps = array_allocate(sizeof(uint32_t), def->constants_length);
int32_t j = 0;
for (int32_t i = 0; i < def->constants_length; i++) {
constant_remaps[i] = j;
def->constants[j] = def->constants[i];
if (bs_read_bit(bitset, i)) {
j++;
}
}
def->constants_length = j;
for (int32_t pc = 0; pc < def->bytecode_length; pc++) {
uint32_t E = code[pc] >> 16;
switch (code[pc] & 0x7F) {
default:
continue;
case JOP_LOAD_CONSTANT:
code[pc] = (code[pc] & 0xFFFF) | (constant_remaps[E] << 16);
continue;
}
}
janet_free(constant_remaps);
}
janet_free(bitset);
}
/* Remove all noops while preserving jumps and debugging information.
* Useful as part of a filtering compiler pass. */
void janet_bytecode_remove_noops(JanetFuncDef *def) {
@@ -1306,7 +1420,8 @@ void janet_bytecode_movopt_full(JanetFuncDef *def, BytecodeBB *blocks, int32_t n
janet_free(bitsets);
}
/* Entry point for optimization */
/* Entry point for optimization. The def should already be valid as determined by janet_verify.
* The compiler may skip this check for performance but the assembler will not. */
void janet_bytecode_optimize(JanetFuncDef *def, int32_t level) {
int32_t delta;
#ifdef JANET_DEBUG
@@ -1334,6 +1449,8 @@ void janet_bytecode_optimize(JanetFuncDef *def, int32_t level) {
total_optimize_fixpoint_loops++;
#endif
} while (delta < 0);
janet_bytecode_remove_unused_constants(def);
janet_bytecode_remove_unused_closures(def);
}
#ifdef JANET_BOOTSTRAP
total_instruction_count += def->bytecode_length;