diff --git a/cl/compile.go b/cl/compile.go
index 4517303e..419618cf 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -543,12 +543,9 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 		x := p.compileValue(b, v.X)
 		ret = b.MakeInterface(t, x)
 	case *ssa.MakeSlice:
-		var nCap llssa.Expr
 		t := p.prog.Type(v.Type(), llssa.InGo)
 		nLen := p.compileValue(b, v.Len)
-		if v.Cap != nil {
-			nCap = p.compileValue(b, v.Cap)
-		}
+		nCap := p.compileValue(b, v.Cap)
 		ret = b.MakeSlice(t, nLen, nCap)
 	case *ssa.MakeMap:
 		var nReserve llssa.Expr
diff --git a/internal/runtime/goarch/goarch.go b/internal/runtime/goarch/goarch.go
new file mode 100644
index 00000000..24c0de95
--- /dev/null
+++ b/internal/runtime/goarch/goarch.go
@@ -0,0 +1,3 @@
+package goarch
+
+const PtrSize = 4 << (^uintptr(0) >> 63)
diff --git a/internal/runtime/math/math.go b/internal/runtime/math/math.go
new file mode 100644
index 00000000..8d38eab8
--- /dev/null
+++ b/internal/runtime/math/math.go
@@ -0,0 +1,15 @@
+package math
+
+import "github.com/goplus/llgo/internal/runtime/goarch"
+
+const MaxUintptr = ^uintptr(0)
+
+// MulUintptr returns a * b and whether the multiplication overflowed.
+// On supported platforms this is an intrinsic lowered by the compiler.
+func MulUintptr(a, b uintptr) (uintptr, bool) {
+	if a|b < 1<<(4*goarch.PtrSize) || a == 0 {
+		return a * b, false
+	}
+	overflow := b > MaxUintptr/a
+	return a * b, overflow
+}
diff --git a/internal/runtime/stubs.go b/internal/runtime/stubs.go
index ed8b9a8d..0b81dc67 100644
--- a/internal/runtime/stubs.go
+++ b/internal/runtime/stubs.go
@@ -36,3 +36,10 @@ func fastrand() uint32 {
 	return s0 + s1
 }
 */
+
+const (
+	// _64bit = 1 on 64-bit systems, 0 on 32-bit systems
+	_64bit       = 1 << (^uintptr(0) >> 63) / 2
+	heapAddrBits = (_64bit)*48 + (1-_64bit)*(32)
+	maxAlloc     = (1 << heapAddrBits) - (1-_64bit)*1
+)
diff --git a/internal/runtime/z_slice.go b/internal/runtime/z_slice.go
index 1d2dcc4a..6eed5167 100644
--- a/internal/runtime/z_slice.go
+++ b/internal/runtime/z_slice.go
@@ -20,6 +20,7 @@ import (
 	"unsafe"
 
 	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/internal/runtime/math"
 )
 
 // -----------------------------------------------------------------------------
@@ -120,32 +121,10 @@ func SliceCopy(dst Slice, data unsafe.Pointer, num int, etSize int) int {
 	return n
 }
 
-const (
-	// _64bit = 1 on 64-bit systems, 0 on 32-bit systems
-	_64bit       = 1 << (^uintptr(0) >> 63) / 2
-	heapAddrBits = (_64bit)*48 + (1-_64bit)*(32)
-	maxAlloc     = (1 << heapAddrBits) - (1-_64bit)*1
-)
-
-const (
-	PtrSize    = 4 << (^uintptr(0) >> 63)
-	MaxUintptr = ^uintptr(0)
-)
-
-// MulUintptr returns a * b and whether the multiplication overflowed.
-// On supported platforms this is an intrinsic lowered by the compiler.
-func MulUintptr(a, b uintptr) (uintptr, bool) {
-	if a|b < 1<<(4*PtrSize) || a == 0 {
-		return a * b, false
-	}
-	overflow := b > MaxUintptr/a
-	return a * b, overflow
-}
-
 func MakeSlice(len, cap int, etSize int) Slice {
-	mem, overflow := MulUintptr(uintptr(etSize), uintptr(cap))
+	mem, overflow := math.MulUintptr(uintptr(etSize), uintptr(cap))
 	if overflow || mem > maxAlloc || len < 0 || len > cap {
-		mem, overflow := MulUintptr(uintptr(etSize), uintptr(len))
+		mem, overflow := math.MulUintptr(uintptr(etSize), uintptr(len))
 		if overflow || mem > maxAlloc || len < 0 {
 			panicmakeslicelen()
 		}
diff --git a/ssa/datastruct.go b/ssa/datastruct.go
index 97e6dd1d..9ce447fa 100644
--- a/ssa/datastruct.go
+++ b/ssa/datastruct.go
@@ -417,11 +417,7 @@ func (b Builder) MakeSlice(t Type, len, cap Expr) (ret Expr) {
 	}
 	prog := b.Prog
 	len = b.fitIntSize(len)
-	if cap.IsNil() {
-		cap = len
-	} else {
-		cap = b.fitIntSize(cap)
-	}
+	cap = b.fitIntSize(cap)
 	telem := prog.Index(t)
 	ret = b.InlineCall(b.Pkg.rtFunc("MakeSlice"), len, cap, prog.IntVal(prog.SizeOf(telem), prog.Int()))
 	ret.Type = t