internal/runtime/maps: use simpler calculation for slot element

This reduces the adds required at the return point from 3 to 1.
(The multiply inside g.elem() does get CSE'd with the one inside
g.key(), but the rest of the adds don't.)

Instead, compute the element as just a fixed offset from the key.

Change-Id: Ia4d7664efafcdca5e9daeb77d270651bb186232c
Reviewed-on: https://go-review.googlesource.com/c/go/+/629535
Reviewed-by: Russ Cox <rsc@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

diff --git a/src/internal/runtime/maps/runtime_fast32_swiss.go b/src/internal/runtime/maps/runtime_fast32_swiss.go
index 2ab30bce6cc6c388956cd71a2cde22c1ce9c3e74..ff5815abdd1d4ddfa61bdf3b9e1cc7473c2bd3ca 100644 (file)
--- a/src/internal/runtime/maps/runtime_fast32_swiss.go
+++ b/src/internal/runtime/maps/runtime_fast32_swiss.go
@@ -66,7 +66,7 @@ func runtime_mapaccess1_fast32(typ *abi.SwissMapType, m *Map, key uint32) unsafe
 
                        slotKey := g.key(typ, i)
                        if key == *(*uint32)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem
                        }
                        match = match.removeFirst()
@@ -134,7 +134,7 @@ func runtime_mapaccess2_fast32(typ *abi.SwissMapType, m *Map, key uint32) (unsaf
 
                        slotKey := g.key(typ, i)
                        if key == *(*uint32)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem, true
                        }
                        match = match.removeFirst()

diff --git a/src/internal/runtime/maps/runtime_fast64_swiss.go b/src/internal/runtime/maps/runtime_fast64_swiss.go
index 396c63c23685eca9df7282c7b9ef5ffa79b4969d..f4716dffdaaf8874754f13788b94625c2d271346 100644 (file)
--- a/src/internal/runtime/maps/runtime_fast64_swiss.go
+++ b/src/internal/runtime/maps/runtime_fast64_swiss.go
@@ -66,7 +66,7 @@ func runtime_mapaccess1_fast64(typ *abi.SwissMapType, m *Map, key uint64) unsafe
 
                        slotKey := g.key(typ, i)
                        if key == *(*uint64)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem
                        }
                        match = match.removeFirst()
@@ -134,7 +134,7 @@ func runtime_mapaccess2_fast64(typ *abi.SwissMapType, m *Map, key uint64) (unsaf
 
                        slotKey := g.key(typ, i)
                        if key == *(*uint64)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem, true
                        }
                        match = match.removeFirst()

diff --git a/src/internal/runtime/maps/runtime_faststr_swiss.go b/src/internal/runtime/maps/runtime_faststr_swiss.go
index 38170a1821fea147efd32a9af56db1f44748d601..eed8d8666d4ebe125af603cf8f3e0524a367f162 100644 (file)
--- a/src/internal/runtime/maps/runtime_faststr_swiss.go
+++ b/src/internal/runtime/maps/runtime_faststr_swiss.go
@@ -141,7 +141,7 @@ func runtime_mapaccess1_faststr(typ *abi.SwissMapType, m *Map, key string) unsaf
 
                        slotKey := g.key(typ, i)
                        if key == *(*string)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem
                        }
                        match = match.removeFirst()
@@ -199,7 +199,7 @@ func runtime_mapaccess2_faststr(typ *abi.SwissMapType, m *Map, key string) (unsa
 
                        slotKey := g.key(typ, i)
                        if key == *(*string)(slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
                                return slotElem, true
                        }
                        match = match.removeFirst()

diff --git a/src/internal/runtime/maps/runtime_swiss.go b/src/internal/runtime/maps/runtime_swiss.go
index 58ac8934866ce4bcf70b4c028ca59388d262f0c6..3f4f970fb7c3f8ec6a9ae41d44c4acd3238e0951 100644 (file)
--- a/src/internal/runtime/maps/runtime_swiss.go
+++ b/src/internal/runtime/maps/runtime_swiss.go
@@ -90,11 +90,12 @@ func runtime_mapaccess1(typ *abi.SwissMapType, m *Map, key unsafe.Pointer) unsaf
                        i := match.first()
 
                        slotKey := g.key(typ, i)
+                       slotKeyOrig := slotKey
                        if typ.IndirectKey() {
                                slotKey = *((*unsafe.Pointer)(slotKey))
                        }
                        if typ.Key.Equal(key, slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKeyOrig) + typ.ElemOff)
                                if typ.IndirectElem() {
                                        slotElem = *((*unsafe.Pointer)(slotElem))
                                }
@@ -163,11 +164,12 @@ func runtime_mapaccess2(typ *abi.SwissMapType, m *Map, key unsafe.Pointer) (unsa
                        i := match.first()
 
                        slotKey := g.key(typ, i)
+                       slotKeyOrig := slotKey
                        if typ.IndirectKey() {
                                slotKey = *((*unsafe.Pointer)(slotKey))
                        }
                        if typ.Key.Equal(key, slotKey) {
-                               slotElem := g.elem(typ, i)
+                               slotElem := unsafe.Pointer(uintptr(slotKeyOrig) + typ.ElemOff)
                                if typ.IndirectElem() {
                                        slotElem = *((*unsafe.Pointer)(slotElem))
                                }
@@ -256,6 +258,7 @@ outer:
                                i := match.first()
 
                                slotKey := g.key(typ, i)
+                               slotKeyOrig := slotKey
                                if typ.IndirectKey() {
                                        slotKey = *((*unsafe.Pointer)(slotKey))
                                }
@@ -264,7 +267,7 @@ outer:
                                                typedmemmove(typ.Key, slotKey, key)
                                        }
 
-                                       slotElem = g.elem(typ, i)
+                                       slotElem = unsafe.Pointer(uintptr(slotKeyOrig) + typ.ElemOff)
                                        if typ.IndirectElem() {
                                                slotElem = *((*unsafe.Pointer)(slotElem))
                                        }
@@ -298,6 +301,7 @@ outer:
                                // If there is room left to grow, just insert the new entry.
                                if t.growthLeft > 0 {
                                        slotKey := g.key(typ, i)
+                                       slotKeyOrig := slotKey
                                        if typ.IndirectKey() {
                                                kmem := newobject(typ.Key)
                                                *(*unsafe.Pointer)(slotKey) = kmem
@@ -305,7 +309,7 @@ outer:
                                        }
                                        typedmemmove(typ.Key, slotKey, key)
 
-                                       slotElem = g.elem(typ, i)
+                                       slotElem = unsafe.Pointer(uintptr(slotKeyOrig) + typ.ElemOff)
                                        if typ.IndirectElem() {
                                                emem := newobject(typ.Elem)
                                                *(*unsafe.Pointer)(slotElem) = emem