internal/runtime/maps: eliminate a load from the hot path

typ.Group.Size involves two loads.

Instead cache GroupSize as a separate fields of the map type
so we can get to it in just one load.

Change-Id: I10ffdce1c7f75dcf448da14040fda78f0d75fd1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/627716
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

3 files changed, 6 insertions, 6 deletions

diff --git a/src/internal/runtime/maps/group.go b/src/internal/runtime/maps/group.go
index 35b39bbc37..aae667c8d8 100644
--- a/src/internal/runtime/maps/group.go
+++ b/src/internal/runtime/maps/group.go
@@ -53,7 +53,7 @@ func (b bitset) removeFirst() bitset {
 // removeBelow removes all set bits below slot i (non-inclusive).
 func (b bitset) removeBelow(i uintptr) bitset {
 	// Clear all bits below slot i's byte.
-	mask := (uint64(1) << (8*uint64(i))) - 1
+	mask := (uint64(1) << (8 * uint64(i))) - 1
 	return b &^ bitset(mask)
 }
 
@@ -239,7 +239,7 @@ func newGroups(typ *abi.SwissMapType, length uint64) groupsReference {
 func (g *groupsReference) group(typ *abi.SwissMapType, i uint64) groupReference {
 	// TODO(prattmic): Do something here about truncation on cast to
 	// uintptr on 32-bit systems?
-	offset := uintptr(i) * typ.Group.Size_
+	offset := uintptr(i) * typ.GroupSize
 
 	return groupReference{
 		data: unsafe.Pointer(uintptr(g.data) + offset),
diff --git a/src/internal/runtime/maps/map.go b/src/internal/runtime/maps/map.go
index 86977bbc2d..969da13432 100644
--- a/src/internal/runtime/maps/map.go
+++ b/src/internal/runtime/maps/map.go
@@ -296,7 +296,7 @@ func NewMap(mt *abi.SwissMapType, hint uintptr, m *Map, maxAlloc uintptr) *Map {
 	if overflow {
 		return m // return an empty map.
 	} else {
-		mem, overflow := math.MulUintptr(groups, mt.Group.Size_)
+		mem, overflow := math.MulUintptr(groups, mt.GroupSize)
 		if overflow || mem > maxAlloc {
 			return m // return an empty map.
 		}
diff --git a/src/internal/runtime/maps/map_test.go b/src/internal/runtime/maps/map_test.go
index 42db55c6a4..160450ebb2 100644
--- a/src/internal/runtime/maps/map_test.go
+++ b/src/internal/runtime/maps/map_test.go
@@ -517,8 +517,8 @@ func testTableIterationGrowDuplicate(t *testing.T, grow int) {
 
 		key := *(*uint32)(keyPtr)
 		elem := *(*uint64)(elemPtr)
-		if elem != 256 + uint64(key) {
-			t.Errorf("iteration got key %d elem %d want elem %d", key, elem, 256 + uint64(key))
+		if elem != 256+uint64(key) {
+			t.Errorf("iteration got key %d elem %d want elem %d", key, elem, 256+uint64(key))
 		}
 		if _, ok := got[key]; ok {
 			t.Errorf("iteration got key %d more than once", key)
@@ -623,7 +623,7 @@ func TestMapZeroSizeSlot(t *testing.T) {
 	tab := m.TableFor(typ, unsafe.Pointer(&key))
 	start := tab.GroupsStart()
 	length := tab.GroupsLength()
-	end := unsafe.Pointer(uintptr(start) + length*typ.Group.Size() - 1) // inclusive to ensure we have a valid pointer
+	end := unsafe.Pointer(uintptr(start) + length*typ.GroupSize - 1) // inclusive to ensure we have a valid pointer
 	if uintptr(got) < uintptr(start) || uintptr(got) > uintptr(end) {
 		t.Errorf("elem address outside groups allocation; got %p want [%p, %p]", got, start, end)
 	}