Faster identity-hashcode primitive; fast path now opencoded by the compiler

basis/compiler/cfg/intrinsics/intrinsics.factor

@@ -33,6 +33,7 @@ IN: compiler.cfg.intrinsics
 {
     { kernel.private:tag [ drop emit-tag ] }
     { kernel.private:getenv [ emit-getenv ] }
+    { kernel.private:(identity-hashcode) [ drop emit-identity-hashcode ] }
     { math.private:both-fixnums? [ drop emit-both-fixnums? ] }
     { math.private:fixnum+ [ drop emit-fixnum+ ] }
     { math.private:fixnum- [ drop emit-fixnum- ] }

basis/compiler/cfg/intrinsics/misc/misc.factor

@@ -1,9 +1,9 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: namespaces layouts sequences kernel
-accessors compiler.tree.propagation.info
-compiler.cfg.stacks compiler.cfg.hats
-compiler.cfg.instructions compiler.cfg.utilities ;
+USING: namespaces layouts sequences kernel math accessors
+compiler.tree.propagation.info compiler.cfg.stacks
+compiler.cfg.hats compiler.cfg.instructions
+compiler.cfg.utilities ;
 IN: compiler.cfg.intrinsics.misc
 
 : emit-tag ( -- )
@@ -14,3 +14,9 @@ IN: compiler.cfg.intrinsics.misc
     swap node-input-infos first literal>>
     [ ds-drop 0 ^^slot-imm ] [ ds-pop ^^offset>slot ^^slot ] if*
     ds-push ;
+
+: emit-identity-hashcode ( -- )
+    ds-pop tag-mask get bitnot ^^load-immediate ^^and 0 0 ^^slot-imm
+    hashcode-shift ^^shr-imm
+    ^^tag-fixnum
+    ds-push ;

basis/stack-checker/known-words/known-words.factor

@@ -713,4 +713,6 @@ M: bad-executable summary
 
 \ profiling { object } { } define-primitive
 
-\ identity-hashcode { object } { fixnum } define-primitive
+\ (identity-hashcode) { object } { fixnum } define-primitive
+
+\ compute-identity-hashcode { object } { } define-primitive

core/bootstrap/layouts/layouts.factor

@@ -30,3 +30,5 @@ H{
     { word 12 }
     { dll 13 }
 } type-numbers set
+
+2 header-bits set

core/bootstrap/primitives.factor

@@ -518,7 +518,8 @@ tuple
     { "<callback>" "alien" (( word -- alien )) }
     { "enable-gc-events" "memory" (( -- )) }
     { "disable-gc-events" "memory" (( -- events )) }
-    { "identity-hashcode" "kernel" (( obj -- code )) }
+    { "(identity-hashcode)" "kernel.private" (( obj -- code )) }
+    { "compute-identity-hashcode" "kernel.private" (( obj -- )) }
 } [ [ first3 ] dip swap make-primitive ] each-index
 
 ! Bump build number

core/kernel/kernel.factor

@@ -192,6 +192,16 @@ M: f hashcode* 2drop 31337 ; inline
 
 : hashcode ( obj -- code ) 3 swap hashcode* ; inline
 
+: identity-hashcode ( obj -- code )
+    dup tag 0 eq? [
+        dup tag 1 eq? [ drop 0 ] [
+            dup (identity-hashcode) dup 0 eq? [
+                drop dup compute-identity-hashcode
+                (identity-hashcode)
+            ] [ nip ] if
+        ] if
+    ] unless ; inline
+
 GENERIC: equal? ( obj1 obj2 -- ? )
 
 M: object equal? 2drop f ; inline

core/layouts/layouts.factor

@@ -16,6 +16,8 @@ SYMBOL: type-numbers
 
 SYMBOL: mega-cache-size
 
+SYMBOL: header-bits
+
 : type-number ( class -- n )
     type-numbers get at ;
 
@@ -23,11 +25,14 @@ SYMBOL: mega-cache-size
     tag-bits get shift ;
 
 : tag-header ( n -- tagged )
-    2 shift ;
+    header-bits get shift ;
 
 : untag-fixnum ( n -- tagged )
     tag-bits get neg shift ;
 
+: hashcode-shift ( -- n )
+    tag-bits get header-bits get + ;
+
 ! We do this in its own compilation unit so that they can be
 ! folded below
 <<

vm/objects.cpp

@@ -19,18 +19,21 @@ void factor_vm::primitive_set_special_object()
 void factor_vm::primitive_identity_hashcode()
 {
 	cell tagged = dpeek();
-	if(immediate_p(tagged))
-		drepl(tagged & ~TAG_MASK);
-	else
-	{
-		object *obj = untag<object>(tagged);
-		if(obj->hashcode() == 0)
-		{
-			/* Use megamorphic_cache_misses as a random source of randomness */
-			obj->set_hashcode(((cell)obj / block_granularity) ^ dispatch_stats.megamorphic_cache_hits);
-		}
-		drepl(tag_fixnum(obj->hashcode()));
-	}
+	object *obj = untag<object>(tagged);
+	drepl(tag_fixnum(obj->hashcode()));
+}
+
+void factor_vm::compute_identity_hashcode(object *obj)
+{
+	object_counter++;
+	if(object_counter == 0) object_counter++;
+	obj->set_hashcode((cell)obj ^ object_counter);
+}
+
+void factor_vm::primitive_compute_identity_hashcode()
+{
+	object *obj = untag<object>(dpop());
+	compute_identity_hashcode(obj);
 }
 
 void factor_vm::primitive_set_slot()

vm/primitives.cpp

@@ -127,6 +127,7 @@ PRIMITIVE_FORWARD(callback)
 PRIMITIVE_FORWARD(enable_gc_events)
 PRIMITIVE_FORWARD(disable_gc_events)
 PRIMITIVE_FORWARD(identity_hashcode)
+PRIMITIVE_FORWARD(compute_identity_hashcode)
 
 const primitive_type primitives[] = {
 	primitive_bignum_to_fixnum,
@@ -290,6 +291,7 @@ const primitive_type primitives[] = {
 	primitive_enable_gc_events,
 	primitive_disable_gc_events,
 	primitive_identity_hashcode,
+	primitive_compute_identity_hashcode,
 };
 
 }

vm/vm.hpp

@@ -81,6 +81,9 @@ struct factor_vm
 	/* Number of entries in a polymorphic inline cache */
 	cell max_pic_size;
 
+	/* Incrementing object counter for identity hashing */
+	cell object_counter;
+
 	// contexts
 	void reset_datastack();
 	void reset_retainstack();
@@ -122,6 +125,8 @@ struct factor_vm
 	void primitive_special_object();
 	void primitive_set_special_object();
 	void primitive_identity_hashcode();
+	void compute_identity_hashcode(object *obj);
+	void primitive_compute_identity_hashcode();
 	cell object_size(cell tagged);
 	cell clone_object(cell obj_);
 	void primitive_clone();