runtime: use better hash for non-empty interface

The implementation 'return 0' results in too many collisions.

LGTM=khr
R=golang-codereviews, adonovan, khr
CC=golang-codereviews, iant, khr, r
https://golang.org/cl/125720044

diff --git a/src/pkg/runtime/alg.go b/src/pkg/runtime/alg.go
index 000d4a18b746cccb21924beb29fcaaca323d9e3a..e2917dabb66faedaa17bbc73a647f4ef7e5bf09a 100644 (file)
--- a/src/pkg/runtime/alg.go
+++ b/src/pkg/runtime/alg.go
@@ -111,7 +111,22 @@ func nohash(a unsafe.Pointer, s uintptr, h uintptr) uintptr {
 func interhash(a *interface {
        f()
 }, s uintptr, h uintptr) uintptr {
-       return 0
+       tab := (*iface)(unsafe.Pointer(a)).tab
+       if tab == nil {
+               return h
+       }
+       t := tab._type
+       fn := goalg(t.alg).hash
+       if **(**uintptr)(unsafe.Pointer(&fn)) == nohashcode {
+               // calling nohash will panic too,
+               // but we can print a better error.
+               panic(errorString("hash of unhashable type " + *t._string))
+       }
+       if uintptr(t.size) <= ptrSize {
+               return c1 * fn(unsafe.Pointer(&(*eface)(unsafe.Pointer(a)).data), uintptr(t.size), h^c0)
+       } else {
+               return c1 * fn((*eface)(unsafe.Pointer(a)).data, uintptr(t.size), h^c0)
+       }
 }
 
 func nilinterhash(a *interface{}, s uintptr, h uintptr) uintptr {

diff --git a/src/pkg/runtime/iface.goc b/src/pkg/runtime/iface.goc
index ec8974647089e176640cf55ccdae3a965e1197df..89c116e127f6cb2e81f2a5c1dc7b2ed3e6dddb55 100644 (file)
--- a/src/pkg/runtime/iface.goc
+++ b/src/pkg/runtime/iface.goc
@@ -475,44 +475,6 @@ func assertE2E2(inter *InterfaceType, e Eface) (ret Eface, ok bool) {
        ok = e.type != nil;
 }
 
-static uintptr
-ifacehash1(void *data, Type *t, uintptr h)
-{
-       Alg *alg;
-       uintptr size;
-       Eface err;
-
-       if(t == nil)
-               return 0;
-
-       alg = t->alg;
-       size = t->size;
-       if(alg->hash->fn == (void(*)())runtime·nohash) {
-               // calling nohash will panic too,
-               // but we can print a better error.
-               runtime·newErrorString(runtime·catstring(runtime·gostringnocopy((byte*)"hash of unhashable type "), *t->string), &err);
-               runtime·panic(err);
-       }
-       if(size <= sizeof(data))
-               return ((uintptr(*)(void**,uintptr,uintptr))alg->hash)(&data, size, h);
-       else
-               return ((uintptr(*)(void*,uintptr,uintptr))alg->hash)(data, size, h);
-}
-
-uintptr
-runtime·ifacehash(Iface a, uintptr h)
-{
-       if(a.tab == nil)
-               return h;
-       return ifacehash1(a.data, a.tab->type, h);
-}
-
-uintptr
-runtime·efacehash(Eface a, uintptr h)
-{
-       return ifacehash1(a.data, a.type, h);
-}
-
 static bool
 ifaceeq1(void *data1, void *data2, Type *t)
 {

diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index e6354d7e9cb6e35abded6ceb9e599fb843a5f5ad..1d1618b0d6e9538c785ba5cf9c46fe0ae90f22c0 100644 (file)
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -651,19 +651,19 @@ enum {
 };
 void   runtime·hashinit(void);
 
-uintptr        runtime·memhash(void*, uintptr, uintptr);
-uintptr        runtime·nohash(void*, uintptr, uintptr);
-uintptr        runtime·strhash(void*, uintptr, uintptr);
-uintptr        runtime·interhash(void*, uintptr, uintptr);
-uintptr        runtime·nilinterhash(void*, uintptr, uintptr);
-uintptr        runtime·f32hash(void*, uintptr, uintptr);
-uintptr        runtime·f64hash(void*, uintptr, uintptr);
-uintptr        runtime·c64hash(void*, uintptr, uintptr);
-uintptr        runtime·c128hash(void*, uintptr, uintptr);
-uintptr        runtime·aeshash(void*, uintptr, uintptr);
-uintptr        runtime·aeshash32(void*, uintptr, uintptr);
-uintptr        runtime·aeshash64(void*, uintptr, uintptr);
-uintptr        runtime·aeshashstr(void*, uintptr, uintptr);
+void   runtime·memhash(void*, uintptr, uintptr, uintptr);
+void   runtime·nohash(void*, uintptr, uintptr, uintptr);
+void   runtime·strhash(void*, uintptr, uintptr, uintptr);
+void   runtime·interhash(void*, uintptr, uintptr, uintptr);
+void   runtime·nilinterhash(void*, uintptr, uintptr, uintptr);
+void   runtime·f32hash(void*, uintptr, uintptr, uintptr);
+void   runtime·f64hash(void*, uintptr, uintptr, uintptr);
+void   runtime·c64hash(void*, uintptr, uintptr, uintptr);
+void   runtime·c128hash(void*, uintptr, uintptr, uintptr);
+void   runtime·aeshash(void*, uintptr, uintptr, uintptr);
+void   runtime·aeshash32(void*, uintptr, uintptr, uintptr);
+void   runtime·aeshash64(void*, uintptr, uintptr, uintptr);
+void   runtime·aeshashstr(void*, uintptr, uintptr, uintptr);
 
 void   runtime·memequal(bool*, uintptr, void*, void*);
 void   runtime·noequal(bool*, uintptr, void*, void*);
@@ -876,8 +876,6 @@ void        runtime·mallocinit(void);
 void   runtime·chaninit(void);
 bool   runtime·ifaceeq_c(Iface, Iface);
 bool   runtime·efaceeq_c(Eface, Eface);
-uintptr        runtime·ifacehash(Iface, uintptr);
-uintptr        runtime·efacehash(Eface, uintptr);
 void*  runtime·malloc(uintptr size);
 void   runtime·runpanic(Panic*);
 uintptr        runtime·getcallersp(void*);