internal/runtime/maps: use matchEmptyOrDeleted instead of matchEmpty

It's a bit more efficient.

Change-Id: If813a597516c41fdac6f60e586641d0ee1cde025
Reviewed-on: https://go-review.googlesource.com/c/go/+/623818
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/internal/runtime/maps/map.go

@@ -554,9 +554,10 @@ func (m *Map) putSlotSmall(typ *abi.SwissMapType, hash uintptr, key unsafe.Point
 		match = match.removeFirst()
 	}
 
-	// No need to look for deleted slots, small maps can't have them (see
-	// deleteSmall).
-	match = g.ctrls().matchEmpty()
+	// There can't be deleted slots, small maps can't have them
+	// (see deleteSmall). Use matchEmptyOrDeleted as it is a bit
+	// more efficient than matchEmpty.
+	match = g.ctrls().matchEmptyOrDeleted()
 	if match == 0 {
 		fatal("small map with no empty slot (concurrent map writes?)")
 	}

src/internal/runtime/maps/runtime_fast32_swiss.go

@@ -160,9 +160,10 @@ func (m *Map) putSlotSmallFast32(typ *abi.SwissMapType, hash uintptr, key uint32
 		match = match.removeFirst()
 	}
 
-	// No need to look for deleted slots, small maps can't have them (see
-	// deleteSmall).
-	match = g.ctrls().matchEmpty()
+	// There can't be deleted slots, small maps can't have them
+	// (see deleteSmall). Use matchEmptyOrDeleted as it is a bit
+	// more efficient than matchEmpty.
+	match = g.ctrls().matchEmptyOrDeleted()
 	if match == 0 {
 		fatal("small map with no empty slot (concurrent map writes?)")
 	}

src/internal/runtime/maps/runtime_fast64_swiss.go

@@ -159,9 +159,10 @@ func (m *Map) putSlotSmallFast64(typ *abi.SwissMapType, hash uintptr, key uint64
 		match = match.removeFirst()
 	}
 
-	// No need to look for deleted slots, small maps can't have them (see
-	// deleteSmall).
-	match = g.ctrls().matchEmpty()
+	// There can't be deleted slots, small maps can't have them
+	// (see deleteSmall). Use matchEmptyOrDeleted as it is a bit
+	// more efficient than matchEmpty.
+	match = g.ctrls().matchEmptyOrDeleted()
 	if match == 0 {
 		fatal("small map with no empty slot (concurrent map writes?)")
 	}
@@ -336,9 +337,10 @@ func (m *Map) putSlotSmallFastPtr(typ *abi.SwissMapType, hash uintptr, key unsaf
 		match = match.removeFirst()
 	}
 
-	// No need to look for deleted slots, small maps can't have them (see
-	// deleteSmall).
-	match = g.ctrls().matchEmpty()
+	// There can't be deleted slots, small maps can't have them
+	// (see deleteSmall). Use matchEmptyOrDeleted as it is a bit
+	// more efficient than matchEmpty.
+	match = g.ctrls().matchEmptyOrDeleted()
 	if match == 0 {
 		fatal("small map with no empty slot (concurrent map writes?)")
 	}

src/internal/runtime/maps/runtime_faststr_swiss.go

@@ -176,9 +176,10 @@ func (m *Map) putSlotSmallFastStr(typ *abi.SwissMapType, hash uintptr, key strin
 		match = match.removeFirst()
 	}
 
-	// No need to look for deleted slots, small maps can't have them (see
-	// deleteSmall).
-	match = g.ctrls().matchEmpty()
+	// There can't be deleted slots, small maps can't have them
+	// (see deleteSmall). Use matchEmptyOrDeleted as it is a bit
+	// more efficient than matchEmpty.
+	match = g.ctrls().matchEmptyOrDeleted()
 	if match == 0 {
 		fatal("small map with no empty slot (concurrent map writes?)")
 	}

src/internal/runtime/maps/table.go

@@ -381,6 +381,8 @@ func (t *table) PutSlot(typ *abi.SwissMapType, m *Map, hash uintptr, key unsafe.
 // Requires that the entry does not exist in the table, and that the table has
 // room for another element without rehashing.
 //
+// Requires that there are no deleted entries in the table.
+//
 // Never returns nil.
 func (t *table) uncheckedPutSlot(typ *abi.SwissMapType, hash uintptr, key unsafe.Pointer) unsafe.Pointer {
 	if t.growthLeft == 0 {
@@ -395,7 +397,7 @@ func (t *table) uncheckedPutSlot(typ *abi.SwissMapType, hash uintptr, key unsafe
 	for ; ; seq = seq.next() {
 		g := t.groups.group(typ, seq.offset)
 
-		match := g.ctrls().matchEmpty()
+		match := g.ctrls().matchEmptyOrDeleted()
 		if match != 0 {
 			i := match.first()
 
@@ -414,9 +416,7 @@ func (t *table) uncheckedPutSlot(typ *abi.SwissMapType, hash uintptr, key unsafe
 				slotElem = emem
 			}
 
-			if g.ctrls().get(i) == ctrlEmpty {
-				t.growthLeft--
-			}
+			t.growthLeft--
 			g.ctrls().set(i, ctrl(h2(hash)))
 			return slotElem
 		}