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authorBjörn Gustavsson <[email protected]>2017-08-29 06:56:42 +0200
committerBjörn Gustavsson <[email protected]>2017-08-29 07:51:47 +0200
commit8b8f013dbe159819136e71f0349620ff8fc45f74 (patch)
tree6f7f3ccf7c3127f0c8b7ef3c4391f2059d496f4f /erts/emulator/beam
parent3aa559f584559af3a76ecd8c2367f59e062dbe0e (diff)
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De-duplicate bignums in the literal pool
Duplicate literals in the literal pool is a waste of memory. Also, having unique literals can simplify some loader optimizations, because we can known that if two literal indices are distinct, the values must be distcint too.
Diffstat (limited to 'erts/emulator/beam')
-rw-r--r--erts/emulator/beam/beam_load.c71
1 files changed, 48 insertions, 23 deletions
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 9ff32e30f3..6cd1287ee0 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -5372,12 +5372,15 @@ get_tag_and_value(LoaderState* stp, Uint len_code,
{
Uint count;
Sint val;
- byte default_buf[128];
- byte* bigbuf = default_buf;
+ byte default_byte_buf[128];
+ byte* byte_buf = default_byte_buf;
+ Eterm default_big_buf[128/sizeof(Eterm)];
+ Eterm* big_buf = default_big_buf;
+ Eterm tmp_big;
byte* s;
int i;
int neg = 0;
- Uint arity;
+ Uint words_needed;
Eterm* hp;
/*
@@ -5454,8 +5457,11 @@ get_tag_and_value(LoaderState* stp, Uint len_code,
*result = val;
return TAG_i;
} else {
- *result = new_literal(stp, &hp, BIG_UINT_HEAP_SIZE);
- (void) small_to_big(val, hp);
+ tmp_big = small_to_big(val, big_buf);
+ if (!find_literal(stp, tmp_big, result)) {
+ *result = new_literal(stp, &hp, BIG_UINT_HEAP_SIZE);
+ sys_memcpy(hp, big_buf, BIG_UINT_HEAP_SIZE*sizeof(Eterm));
+ }
return TAG_q;
}
}
@@ -5465,8 +5471,8 @@ get_tag_and_value(LoaderState* stp, Uint len_code,
* (including margin).
*/
- if (count+8 > sizeof(default_buf)) {
- bigbuf = erts_alloc(ERTS_ALC_T_LOADER_TMP, count+8);
+ if (count+8 > sizeof(default_byte_buf)) {
+ byte_buf = erts_alloc(ERTS_ALC_T_LOADER_TMP, count+8);
}
/*
@@ -5475,20 +5481,20 @@ get_tag_and_value(LoaderState* stp, Uint len_code,
GetString(stp, s, count);
for (i = 0; i < count; i++) {
- bigbuf[count-i-1] = *s++;
+ byte_buf[count-i-1] = *s++;
}
/*
* Check if the number is negative, and negate it if so.
*/
- if ((bigbuf[count-1] & 0x80) != 0) {
+ if ((byte_buf[count-1] & 0x80) != 0) {
unsigned carry = 1;
neg = 1;
for (i = 0; i < count; i++) {
- bigbuf[i] = ~bigbuf[i] + carry;
- carry = (bigbuf[i] == 0 && carry == 1);
+ byte_buf[i] = ~byte_buf[i] + carry;
+ carry = (byte_buf[i] == 0 && carry == 1);
}
ASSERT(carry == 0);
}
@@ -5497,33 +5503,52 @@ get_tag_and_value(LoaderState* stp, Uint len_code,
* Align to word boundary.
*/
- if (bigbuf[count-1] == 0) {
+ if (byte_buf[count-1] == 0) {
count--;
}
- if (bigbuf[count-1] == 0) {
+ if (byte_buf[count-1] == 0) {
LoadError0(stp, "bignum not normalized");
}
while (count % sizeof(Eterm) != 0) {
- bigbuf[count++] = 0;
+ byte_buf[count++] = 0;
}
/*
- * Allocate heap space for the bignum and copy it.
+ * Convert to a bignum.
*/
- arity = count/sizeof(Eterm);
- *result = new_literal(stp, &hp, arity+1);
- if (is_nil(bytes_to_big(bigbuf, count, neg, hp)))
- goto load_error;
+ words_needed = count/sizeof(Eterm) + 1;
+ if (words_needed*sizeof(Eterm) > sizeof(default_big_buf)) {
+ big_buf = erts_alloc(ERTS_ALC_T_LOADER_TMP, words_needed*sizeof(Eterm));
+ }
+ tmp_big = bytes_to_big(byte_buf, count, neg, big_buf);
+ if (is_nil(tmp_big)) {
+ goto load_error;
+ }
- if (bigbuf != default_buf) {
- erts_free(ERTS_ALC_T_LOADER_TMP, (void *) bigbuf);
+ /*
+ * Create a literal if there is no previous literal with the same value.
+ */
+
+ if (!find_literal(stp, tmp_big, result)) {
+ *result = new_literal(stp, &hp, words_needed);
+ sys_memcpy(hp, big_buf, words_needed*sizeof(Eterm));
+ }
+
+ if (byte_buf != default_byte_buf) {
+ erts_free(ERTS_ALC_T_LOADER_TMP, (void *) byte_buf);
+ }
+ if (big_buf != default_big_buf) {
+ erts_free(ERTS_ALC_T_LOADER_TMP, (void *) big_buf);
}
return TAG_q;
load_error:
- if (bigbuf != default_buf) {
- erts_free(ERTS_ALC_T_LOADER_TMP, (void *) bigbuf);
+ if (byte_buf != default_byte_buf) {
+ erts_free(ERTS_ALC_T_LOADER_TMP, (void *) byte_buf);
+ }
+ if (big_buf != default_big_buf) {
+ erts_free(ERTS_ALC_T_LOADER_TMP, (void *) big_buf);
}
return -1;
}