AssemblyScript
diff --git a/src/compiler.ts b/src/compiler.ts
@@ -193,7 +193,8 @@ import {
   writeF32,
   writeF64,
   uniqueMap,
-  isPowerOf2
+  isPowerOf2,
+  v128_zero
 } from "./util";
 
 /** Compiler options. */
@@ -3058,10 +3059,11 @@ export class Compiler extends DiagnosticEmitter {
         if (initExpr) {
           let precomp = module.runExpression(initExpr, ExpressionRunnerFlags.PreserveSideeffects);
           if (precomp) {
-            initExpr = precomp;
-            let local = new Local(name, -1, type, flow.parentFunction);
+            initExpr = precomp; // always use precomputed initExpr
+            let local: Local | null = null;
             switch (<u32>getExpressionType(initExpr)) {
               case <u32>NativeType.I32: {
+                local = new Local(name, -1, type, flow.parentFunction);
                 local.setConstantIntegerValue(
                   i64_new(
                     getConstValueI32(initExpr),
@@ -3072,6 +3074,7 @@ export class Compiler extends DiagnosticEmitter {
                 break;
               }
               case <u32>NativeType.I64: {
+                local = new Local(name, -1, type, flow.parentFunction);
                 local.setConstantIntegerValue(
                   i64_new(
                     getConstValueI64Low(initExpr),
@@ -3082,33 +3085,33 @@ export class Compiler extends DiagnosticEmitter {
                 break;
               }
               case <u32>NativeType.F32: {
+                local = new Local(name, -1, type, flow.parentFunction);
                 local.setConstantFloatValue(<f64>getConstValueF32(initExpr), type);
                 break;
               }
               case <u32>NativeType.F64: {
+                local = new Local(name, -1, type, flow.parentFunction);
                 local.setConstantFloatValue(getConstValueF64(initExpr), type);
                 break;
               }
-              default: {
-                assert(false);
-                return module.unreachable();
-              }
             }
-            // Create a virtual local that doesn't actually exist in WebAssembly
-            let scopedLocals = flow.scopedLocals;
-            if (!scopedLocals) flow.scopedLocals = scopedLocals = new Map();
-            else if (scopedLocals.has(name)) {
-              let existing = assert(scopedLocals.get(name));
-              this.errorRelated(
-                DiagnosticCode.Duplicate_identifier_0,
-                declaration.name.range,
-                existing.declaration.name.range,
-                name
-              );
-              return this.module.unreachable();
+            if (local) {
+              // Add as a virtual local that doesn't actually exist in WebAssembly
+              let scopedLocals = flow.scopedLocals;
+              if (!scopedLocals) flow.scopedLocals = scopedLocals = new Map();
+              else if (scopedLocals.has(name)) {
+                let existing = assert(scopedLocals.get(name));
+                this.errorRelated(
+                  DiagnosticCode.Duplicate_identifier_0,
+                  declaration.name.range,
+                  existing.declaration.name.range,
+                  name
+                );
+                return this.module.unreachable();
+              }
+              scopedLocals.set(name, local);
+              isStatic = true;
             }
-            scopedLocals.set(name, local);
-            isStatic = true;
           }
         } else {
           this.error(
@@ -11035,8 +11038,6 @@ export class Compiler extends DiagnosticEmitter {
 
 // helpers
 
-const v128_zero = new Uint8Array(16);
-
 function mangleImportName(
   element: Element,
   declaration: DeclarationStatement

diff --git a/src/util/index.ts b/src/util/index.ts
@@ -8,3 +8,4 @@ export * from "./collections";
 export * from "./math";
 export * from "./path";
 export * from "./text";
+export * from "./vector";
diff --git a/src/util/vector.ts b/src/util/vector.ts
@@ -0,0 +1,7 @@
+/**
+ * @fileoverview Various vector utility.
+ * @license Apache-2.0
+ */
+
+/** v128 zero constant. */
+export const v128_zero = new Uint8Array(16);
diff --git a/tests/compiler/features/simd.ts b/tests/compiler/features/simd.ts
@@ -683,6 +683,11 @@ function test_v64x2(): void {
   // }
 }
 
+function test_const(): v128 {
+  const one = i32x4.splat(1); // should precompute
+  return one;                 // should not inline
+}
+
 if (ASC_FEATURE_SIMD) {
   test_v128();
   test_i8x16();
@@ -695,4 +700,5 @@ if (ASC_FEATURE_SIMD) {
   test_v16x8();
   test_v32x4();
   test_v64x2();
+  test_const();
 }
diff --git a/tests/compiler/features/simd.untouched.wat b/tests/compiler/features/simd.untouched.wat
@@ -3,6 +3,7 @@
  (type $i32_=>_none (func (param i32)))
  (type $i32_i32_i32_i32_=>_none (func (param i32 i32 i32 i32)))
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
+ (type $none_=>_v128 (func (result v128)))
  (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
  (memory $0 1)
  (data (i32.const 16) "\1e\00\00\00\01\00\00\00\01\00\00\00\1e\00\00\00~\00l\00i\00b\00/\00r\00t\00/\00s\00t\00u\00b\00.\00t\00s\00")
@@ -2989,6 +2990,12 @@
  (func $features/simd/test_v64x2
   nop
  )
+ (func $features/simd/test_const (result v128)
+  (local $0 v128)
+  v128.const i32x4 0x00000001 0x00000001 0x00000001 0x00000001
+  local.set $0
+  local.get $0
+ )
  (func $start:features/simd
   global.get $~lib/heap/__heap_base
   i32.const 15
@@ -3013,6 +3020,8 @@
   call $features/simd/test_v16x8
   call $features/simd/test_v32x4
   call $features/simd/test_v64x2
+  call $features/simd/test_const
+  drop
  )
  (func $~start
   call $start:features/simd