diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules
index 00e8fcbe32e..8583cfae40c 100644
--- a/src/cmd/compile/internal/ssa/_gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/_gen/generic.rules
@@ -989,6 +989,10 @@
     (Const64 <typ.Int> [0])
     (Const64 <typ.Int> [0]))
 
+// Special rule to help constant slicing; len > 0 implies cap > 0 implies Slicemask is all 1
+(SliceMake (AddPtr <t> x (And64 y (Slicemask _))) w:(Const64 [c]) z) && c > 0 => (SliceMake (AddPtr <t> x y) w z)
+(SliceMake (AddPtr <t> x (And32 y (Slicemask _))) w:(Const32 [c]) z) && c > 0 => (SliceMake (AddPtr <t> x y) w z)
+
 // interface ops
 (ConstInterface) =>
   (IMake
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index fe61ceaff2e..c9cff8651b7 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -422,6 +422,8 @@ func rewriteValuegeneric(v *Value) bool {
 		return rewriteValuegeneric_OpSliceCap(v)
 	case OpSliceLen:
 		return rewriteValuegeneric_OpSliceLen(v)
+	case OpSliceMake:
+		return rewriteValuegeneric_OpSliceMake(v)
 	case OpSlicePtr:
 		return rewriteValuegeneric_OpSlicePtr(v)
 	case OpSlicemask:
@@ -30645,6 +30647,91 @@ func rewriteValuegeneric_OpSliceLen(v *Value) bool {
 	}
 	return false
 }
+func rewriteValuegeneric_OpSliceMake(v *Value) bool {
+	v_2 := v.Args[2]
+	v_1 := v.Args[1]
+	v_0 := v.Args[0]
+	b := v.Block
+	// match: (SliceMake (AddPtr <t> x (And64 y (Slicemask _))) w:(Const64 [c]) z)
+	// cond: c > 0
+	// result: (SliceMake (AddPtr <t> x y) w z)
+	for {
+		if v_0.Op != OpAddPtr {
+			break
+		}
+		t := v_0.Type
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpAnd64 {
+			break
+		}
+		_ = v_0_1.Args[1]
+		v_0_1_0 := v_0_1.Args[0]
+		v_0_1_1 := v_0_1.Args[1]
+		for _i0 := 0; _i0 <= 1; _i0, v_0_1_0, v_0_1_1 = _i0+1, v_0_1_1, v_0_1_0 {
+			y := v_0_1_0
+			if v_0_1_1.Op != OpSlicemask {
+				continue
+			}
+			w := v_1
+			if w.Op != OpConst64 {
+				continue
+			}
+			c := auxIntToInt64(w.AuxInt)
+			z := v_2
+			if !(c > 0) {
+				continue
+			}
+			v.reset(OpSliceMake)
+			v0 := b.NewValue0(v.Pos, OpAddPtr, t)
+			v0.AddArg2(x, y)
+			v.AddArg3(v0, w, z)
+			return true
+		}
+		break
+	}
+	// match: (SliceMake (AddPtr <t> x (And32 y (Slicemask _))) w:(Const32 [c]) z)
+	// cond: c > 0
+	// result: (SliceMake (AddPtr <t> x y) w z)
+	for {
+		if v_0.Op != OpAddPtr {
+			break
+		}
+		t := v_0.Type
+		_ = v_0.Args[1]
+		x := v_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpAnd32 {
+			break
+		}
+		_ = v_0_1.Args[1]
+		v_0_1_0 := v_0_1.Args[0]
+		v_0_1_1 := v_0_1.Args[1]
+		for _i0 := 0; _i0 <= 1; _i0, v_0_1_0, v_0_1_1 = _i0+1, v_0_1_1, v_0_1_0 {
+			y := v_0_1_0
+			if v_0_1_1.Op != OpSlicemask {
+				continue
+			}
+			w := v_1
+			if w.Op != OpConst32 {
+				continue
+			}
+			c := auxIntToInt32(w.AuxInt)
+			z := v_2
+			if !(c > 0) {
+				continue
+			}
+			v.reset(OpSliceMake)
+			v0 := b.NewValue0(v.Pos, OpAddPtr, t)
+			v0.AddArg2(x, y)
+			v.AddArg3(v0, w, z)
+			return true
+		}
+		break
+	}
+	return false
+}
 func rewriteValuegeneric_OpSlicePtr(v *Value) bool {
 	v_0 := v.Args[0]
 	// match: (SlicePtr (SliceMake (SlicePtr x) _ _))
diff --git a/test/prove.go b/test/prove.go
index 70a27865cfd..6d2bb0962be 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -511,10 +511,10 @@ func f19() (e int64, err error) {
 
 func sm1(b []int, x int) {
 	// Test constant argument to slicemask.
-	useSlice(b[2:8]) // ERROR "Proved slicemask not needed$"
+	useSlice(b[2:8]) // optimized away earlier by rewrite
 	// Test non-constant argument with known limits.
 	if cap(b) > 10 {
-		useSlice(b[2:])
+		useSlice(b[2:]) // ERROR "Proved slicemask not needed$"
 	}
 }