mirror of https://github.com/odrling/Aegisub
84 lines
3.0 KiB
Diff
84 lines
3.0 KiB
Diff
From fcf86b84772735a3195af034d0bc7ed0f4106337 Mon Sep 17 00:00:00 2001
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From: Luke Gorrie <luke@snabb.co>
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Date: Wed, 3 Jan 2018 13:04:56 +0000
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Subject: [PATCH] lj_str.c: Remove special-case string interning fastpath
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lj_str_new() had a separate fast-path and slow-path. This was bad
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because (a) the fast-path was complex and (b) the fast-path was
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actually slower than the slow-path in practice and (c) in practice it
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could cause confusing performance problems depending on the memory
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alignment of any often-reused string buffers in a program.
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This change specifically makes the 'life' benchmark faster and more
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robust to memory layout.
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---
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src/lj_str.c | 47 +++++++----------------------------------------
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1 file changed, 7 insertions(+), 40 deletions(-)
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diff --git a/src/lj_str.c b/src/lj_str.c
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index b32d1398..d8f314ae 100644
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--- a/src/lj_str.c
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+++ b/src/lj_str.c
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@@ -37,27 +37,6 @@ int32_t lj_str_cmp(GCstr *a, GCstr *b)
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return (int32_t)(a->len - b->len);
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}
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-/* Fast string data comparison. Caveat: unaligned access to 1st string! */
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-static LJ_AINLINE int str_fastcmp(const char *a, const char *b, MSize len)
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-{
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- MSize i = 0;
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- lua_assert(len > 0);
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- lua_assert((((uintptr_t)a+len-1) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4);
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- do { /* Note: innocuous access up to end of string + 3. */
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- uint32_t v = lj_getu32(a+i) ^ *(const uint32_t *)(b+i);
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- if (v) {
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- i -= len;
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-#if LJ_LE
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- return (int32_t)i >= -3 ? (v << (32+(i<<3))) : 1;
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-#else
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- return (int32_t)i >= -3 ? (v >> (32+(i<<3))) : 1;
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-#endif
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- }
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- i += 4;
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- } while (i < len);
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- return 0;
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-}
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-
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/* Find fixed string p inside string s. */
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const char *lj_str_find(const char *s, const char *p, MSize slen, MSize plen)
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{
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@@ -149,26 +128,14 @@ GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
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h ^= b; h -= lj_rol(b, 16);
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/* Check if the string has already been interned. */
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o = gcref(g->strhash[h & g->strmask]);
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- if (LJ_LIKELY((((uintptr_t)str+len-1) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4)) {
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- while (o != NULL) {
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- GCstr *sx = gco2str(o);
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- if (sx->len == len && str_fastcmp(str, strdata(sx), len) == 0) {
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- /* Resurrect if dead. Can only happen with fixstring() (keywords). */
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- if (isdead(g, o)) flipwhite(o);
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- return sx; /* Return existing string. */
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- }
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- o = gcnext(o);
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- }
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- } else { /* Slow path: end of string is too close to a page boundary. */
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- while (o != NULL) {
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- GCstr *sx = gco2str(o);
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- if (sx->len == len && memcmp(str, strdata(sx), len) == 0) {
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- /* Resurrect if dead. Can only happen with fixstring() (keywords). */
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- if (isdead(g, o)) flipwhite(o);
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- return sx; /* Return existing string. */
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- }
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- o = gcnext(o);
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+ while (o != NULL) {
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+ GCstr *sx = gco2str(o);
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+ if (sx->len == len && memcmp(str, strdata(sx), len) == 0) {
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+ /* Resurrect if dead. Can only happen with fixstring() (keywords). */
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+ if (isdead(g, o)) flipwhite(o);
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+ return sx; /* Return existing string. */
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}
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+ o = gcnext(o);
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}
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/* Nope, create a new string. */
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s = lj_mem_newt(L, sizeof(GCstr)+len+1, GCstr);
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