[release-branch.go1] runtime: improved continuity in hash computation
««« backport c8d163b7930e
runtime: improved continuity in hash computation
Fixes #3695.
R=r, dave, rsc
CC=golang-dev
https://golang.org/cl/6304062
»»»
diff --git a/src/pkg/runtime/alg.c b/src/pkg/runtime/alg.c
index e3c4291..36973eb 100644
--- a/src/pkg/runtime/alg.c
+++ b/src/pkg/runtime/alg.c
@@ -5,6 +5,9 @@
#include "runtime.h"
#include "type.h"
+#define M0 (sizeof(uintptr)==4 ? 2860486313UL : 33054211828000289ULL)
+#define M1 (sizeof(uintptr)==4 ? 3267000013UL : 23344194077549503ULL)
+
/*
* map and chan helpers for
* dealing with unknown types
@@ -16,19 +19,13 @@
uintptr hash;
b = a;
- if(sizeof(hash) == 4)
- hash = 2860486313U;
- else
- hash = 33054211828000289ULL;
+ hash = M0;
while(s > 0) {
- if(sizeof(hash) == 4)
- hash = (hash ^ *b) * 3267000013UL;
- else
- hash = (hash ^ *b) * 23344194077549503ULL;
+ hash = (hash ^ *b) * M1;
b++;
s--;
}
- *h ^= hash;
+ *h = (*h ^ hash) * M1;
}
void
@@ -252,7 +249,7 @@
hash = runtime·fastrand1(); // any kind of NaN
else
hash = *(uint32*)a;
- *h ^= (*h ^ hash ^ 2860486313U) * 3267000013U;
+ *h = (*h ^ hash ^ M0) * M1;
}
void
@@ -271,14 +268,11 @@
else {
u = *(uint64*)a;
if(sizeof(uintptr) == 4)
- hash = ((uint32)(u>>32) * 3267000013UL) ^ (uint32)u;
+ hash = ((uint32)(u>>32) * M1) ^ (uint32)u;
else
hash = u;
}
- if(sizeof(uintptr) == 4)
- *h = (*h ^ hash ^ 2860486313U) * 3267000013U;
- else
- *h = (*h ^ hash ^ 33054211828000289ULL) * 23344194077549503ULL;
+ *h = (*h ^ hash ^ M0) * M1;
}
void
@@ -357,7 +351,7 @@
runtime·interhash(uintptr *h, uintptr s, void *a)
{
USED(s);
- *h ^= runtime·ifacehash(*(Iface*)a);
+ *h = (*h ^ runtime·ifacehash(*(Iface*)a)) * M1;
}
void
@@ -391,7 +385,7 @@
runtime·nilinterhash(uintptr *h, uintptr s, void *a)
{
USED(s);
- *h ^= runtime·efacehash(*(Eface*)a);
+ *h = (*h ^ runtime·efacehash(*(Eface*)a)) * M1;
}
void
