diff --git a/src/builtins.ts b/src/builtins.ts
index a3171074ef..fd7dfae38e 100644
--- a/src/builtins.ts
+++ b/src/builtins.ts
@@ -3542,20 +3542,39 @@ function builtin_i8x16(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(16);
+  var numVars = 0;
+
   for (let i = 0; i < 16; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.i8, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       writeI8(getConstValueI32(precomp), bytes, i);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 16;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatI8x16, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 16; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneI8x16, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.i8x16, builtin_i8x16);
 
@@ -3573,20 +3592,39 @@ function builtin_i16x8(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(8);
+  var numVars = 0;
+
   for (let i = 0; i < 8; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.i16, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       writeI16(getConstValueI32(precomp), bytes, i << 1);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 8;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatI16x8, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 8; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneI16x8, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.i16x8, builtin_i16x8);
 
@@ -3604,20 +3642,39 @@ function builtin_i32x4(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(4);
+  var numVars = 0;
+
   for (let i = 0; i < 4; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.i32, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       writeI32(getConstValueI32(precomp), bytes, i << 2);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 4;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatI32x4, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 4; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneI32x4, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.i32x4, builtin_i32x4);
 
@@ -3635,22 +3692,41 @@ function builtin_i64x2(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(2);
+  var numVars = 0;
+
   for (let i = 0; i < 2; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.i64, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       let off = i << 3;
-      writeI32(getConstValueI64Low(precomp), bytes, off);
+      writeI32(getConstValueI64Low(precomp),  bytes, off + 0);
       writeI32(getConstValueI64High(precomp), bytes, off + 4);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 2;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatI64x2, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 2; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneI64x2, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.i64x2, builtin_i64x2);
 
@@ -3668,20 +3744,39 @@ function builtin_f32x4(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(4);
+  var numVars = 0;
+
   for (let i = 0; i < 4; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.f32, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       writeF32(getConstValueF32(precomp), bytes, i << 2);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 4;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatF32x4, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 4; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneF32x4, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.f32x4, builtin_f32x4);
 
@@ -3699,20 +3794,39 @@ function builtin_f64x2(ctx: BuiltinContext): ExpressionRef {
   }
   var operands = ctx.operands;
   var bytes = new Uint8Array(16);
+  var vars  = new Array<ExpressionRef>(2);
+  var numVars = 0;
+
   for (let i = 0; i < 2; ++i) {
     let expr = compiler.compileExpression(operands[i], Type.f64, Constraints.CONV_IMPLICIT);
     let precomp = module.runExpression(expr, ExpressionRunnerFlags.PreserveSideeffects);
     if (precomp) {
       writeF64(getConstValueF64(precomp), bytes, i << 3);
     } else {
-      compiler.error(
-        DiagnosticCode.Expression_must_be_a_compile_time_constant,
-        operands[i].range
-      );
+      vars[i] = expr;
+      numVars++;
     }
   }
   compiler.currentType = Type.v128;
-  return module.v128(bytes);
+  if (numVars == 0) {
+    // all constants
+    return module.v128(bytes);
+  } else {
+    let vec: ExpressionRef;
+    let fullVars = numVars == 2;
+    if (fullVars) {
+      // all variants
+      vec = module.unary(UnaryOp.SplatF64x2, vars[0]);
+    } else {
+      // mixed constants / variants
+      vec = module.v128(bytes);
+    }
+    for (let i = i32(fullVars); i < 2; i++) {
+      let expr = vars[i];
+      if (expr) vec = module.simd_replace(SIMDReplaceOp.ReplaceLaneF64x2, vec, <u8>i, expr);
+    }
+    return vec;
+  }
 }
 builtins.set(BuiltinNames.f64x2, builtin_f64x2);
 
diff --git a/tests/compiler/simd.debug.wat b/tests/compiler/simd.debug.wat
index d226d7e47d..3d25728865 100644
--- a/tests/compiler/simd.debug.wat
+++ b/tests/compiler/simd.debug.wat
@@ -2,12 +2,22 @@
  (type $none_=>_none (func))
  (type $i32_i32_=>_none (func (param i32 i32)))
  (type $i32_=>_i32 (func (param i32) (result i32)))
+ (type $i32_i32_i32_=>_v128 (func (param i32 i32 i32) (result v128)))
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
  (type $i32_i32_i32_i32_=>_none (func (param i32 i32 i32 i32)))
  (type $i32_i32_i32_=>_i32 (func (param i32 i32 i32) (result i32)))
  (type $i32_i32_i32_=>_none (func (param i32 i32 i32)))
  (type $i32_=>_none (func (param i32)))
  (type $none_=>_v128 (func (result v128)))
+ (type $i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32) (result v128)))
+ (type $i32_i32_i32_i32_i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32 i32 i32 i32 i32) (result v128)))
+ (type $i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32) (result v128)))
+ (type $i64_=>_v128 (func (param i64) (result v128)))
+ (type $i64_i64_=>_v128 (func (param i64 i64) (result v128)))
+ (type $f32_f32_f32_=>_v128 (func (param f32 f32 f32) (result v128)))
+ (type $f32_f32_f32_f32_=>_v128 (func (param f32 f32 f32 f32) (result v128)))
+ (type $f64_=>_v128 (func (param f64) (result v128)))
+ (type $f64_f64_=>_v128 (func (param f64 f64) (result v128)))
  (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
  (global $~lib/native/ASC_FEATURE_SIMD i32 (i32.const 1))
  (global $~lib/rt/tlsf/ROOT (mut i32) (i32.const 0))
@@ -26,6 +36,18 @@
  (data (i32.const 140) ",\00\00\00\00\00\00\00\00\00\00\00\01\00\00\00\0e\00\00\00s\00i\00m\00d\00.\00t\00s\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
  (table $0 1 funcref)
  (elem $0 (i32.const 1))
+ (export "test_vars_i8x16_partial" (func $simd/test_vars_i8x16_partial))
+ (export "test_vars_i8x16_full" (func $simd/test_vars_i8x16_full))
+ (export "test_vars_i16x8_partial" (func $simd/test_vars_i16x8_partial))
+ (export "test_vars_i16x8_full" (func $simd/test_vars_i16x8_full))
+ (export "test_vars_i32x4_partial" (func $simd/test_vars_i32x4_partial))
+ (export "test_vars_i32x4_full" (func $simd/test_vars_i32x4_full))
+ (export "test_vars_i64x2_partial" (func $simd/test_vars_i64x2_partial))
+ (export "test_vars_i64x2_full" (func $simd/test_vars_i64x2_full))
+ (export "test_vars_f32x4_partial" (func $simd/test_vars_f32x4_partial))
+ (export "test_vars_f32x4_full" (func $simd/test_vars_f32x4_full))
+ (export "test_vars_f64x2_partial" (func $simd/test_vars_f64x2_partial))
+ (export "test_vars_f64x2_full" (func $simd/test_vars_f64x2_full))
  (export "memory" (memory $0))
  (start $~start)
  (func $~lib/rt/tlsf/Root#set:flMap (param $0 i32) (param $1 i32)
@@ -4645,6 +4667,136 @@
   call $simd/test_const
   drop
  )
+ (func $simd/test_vars_i8x16_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x03000100 0x07000504 0x0b0a0908 0x000e0d0c
+  local.get $0
+  i8x16.replace_lane 2
+  local.get $1
+  i8x16.replace_lane 6
+  local.get $2
+  i8x16.replace_lane 15
+ )
+ (func $simd/test_vars_i8x16_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (param $4 i32) (param $5 i32) (param $6 i32) (param $7 i32) (param $8 i32) (param $9 i32) (param $10 i32) (param $11 i32) (param $12 i32) (param $13 i32) (param $14 i32) (param $15 i32) (result v128)
+  local.get $0
+  i8x16.splat
+  local.get $1
+  i8x16.replace_lane 1
+  local.get $2
+  i8x16.replace_lane 2
+  local.get $3
+  i8x16.replace_lane 3
+  local.get $4
+  i8x16.replace_lane 4
+  local.get $5
+  i8x16.replace_lane 5
+  local.get $6
+  i8x16.replace_lane 6
+  local.get $7
+  i8x16.replace_lane 7
+  local.get $8
+  i8x16.replace_lane 8
+  local.get $9
+  i8x16.replace_lane 9
+  local.get $10
+  i8x16.replace_lane 10
+  local.get $11
+  i8x16.replace_lane 11
+  local.get $12
+  i8x16.replace_lane 12
+  local.get $13
+  i8x16.replace_lane 13
+  local.get $14
+  i8x16.replace_lane 14
+  local.get $15
+  i8x16.replace_lane 15
+ )
+ (func $simd/test_vars_i16x8_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x00010000 0x00030000 0x00050000 0x00000006
+  local.get $0
+  i16x8.replace_lane 2
+  local.get $1
+  i16x8.replace_lane 4
+  local.get $2
+  i16x8.replace_lane 7
+ )
+ (func $simd/test_vars_i16x8_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (param $4 i32) (param $5 i32) (param $6 i32) (param $7 i32) (result v128)
+  local.get $0
+  i16x8.splat
+  local.get $1
+  i16x8.replace_lane 1
+  local.get $2
+  i16x8.replace_lane 2
+  local.get $3
+  i16x8.replace_lane 3
+  local.get $4
+  i16x8.replace_lane 4
+  local.get $5
+  i16x8.replace_lane 5
+  local.get $6
+  i16x8.replace_lane 6
+  local.get $7
+  i16x8.replace_lane 7
+ )
+ (func $simd/test_vars_i32x4_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  i32x4.replace_lane 1
+  local.get $1
+  i32x4.replace_lane 2
+  local.get $2
+  i32x4.replace_lane 3
+ )
+ (func $simd/test_vars_i32x4_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (result v128)
+  local.get $0
+  i32x4.splat
+  local.get $1
+  i32x4.replace_lane 1
+  local.get $2
+  i32x4.replace_lane 2
+  local.get $3
+  i32x4.replace_lane 3
+ )
+ (func $simd/test_vars_i64x2_partial (param $0 i64) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  i64x2.replace_lane 1
+ )
+ (func $simd/test_vars_i64x2_full (param $0 i64) (param $1 i64) (result v128)
+  local.get $0
+  i64x2.splat
+  local.get $1
+  i64x2.replace_lane 1
+ )
+ (func $simd/test_vars_f32x4_partial (param $0 f32) (param $1 f32) (param $2 f32) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  f32x4.replace_lane 1
+  local.get $1
+  f32x4.replace_lane 2
+  local.get $2
+  f32x4.replace_lane 3
+ )
+ (func $simd/test_vars_f32x4_full (param $0 f32) (param $1 f32) (param $2 f32) (param $3 f32) (result v128)
+  local.get $0
+  f32x4.splat
+  local.get $1
+  f32x4.replace_lane 1
+  local.get $2
+  f32x4.replace_lane 2
+  local.get $3
+  f32x4.replace_lane 3
+ )
+ (func $simd/test_vars_f64x2_partial (param $0 f64) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  f64x2.replace_lane 1
+ )
+ (func $simd/test_vars_f64x2_full (param $0 f64) (param $1 f64) (result v128)
+  local.get $0
+  f64x2.splat
+  local.get $1
+  f64x2.replace_lane 1
+ )
  (func $~start
   call $start:simd
  )
diff --git a/tests/compiler/simd.release.wat b/tests/compiler/simd.release.wat
index d017cdf643..1bab3c700b 100644
--- a/tests/compiler/simd.release.wat
+++ b/tests/compiler/simd.release.wat
@@ -1,10 +1,20 @@
 (module
+ (type $i32_i32_i32_=>_v128 (func (param i32 i32 i32) (result v128)))
  (type $i32_i32_=>_none (func (param i32 i32)))
  (type $none_=>_none (func))
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
  (type $i32_i32_i32_i32_=>_none (func (param i32 i32 i32 i32)))
  (type $i32_i32_i32_=>_none (func (param i32 i32 i32)))
  (type $i32_=>_none (func (param i32)))
+ (type $i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32 i32) (result v128)))
+ (type $i32_i32_i32_i32_i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32 i32 i32 i32 i32) (result v128)))
+ (type $i32_i32_i32_i32_=>_v128 (func (param i32 i32 i32 i32) (result v128)))
+ (type $i64_=>_v128 (func (param i64) (result v128)))
+ (type $i64_i64_=>_v128 (func (param i64 i64) (result v128)))
+ (type $f32_f32_f32_=>_v128 (func (param f32 f32 f32) (result v128)))
+ (type $f32_f32_f32_f32_=>_v128 (func (param f32 f32 f32 f32) (result v128)))
+ (type $f64_=>_v128 (func (param f64) (result v128)))
+ (type $f64_f64_=>_v128 (func (param f64 f64) (result v128)))
  (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
  (global $~lib/rt/tlsf/ROOT (mut i32) (i32.const 0))
  (memory $0 1)
@@ -14,6 +24,18 @@
  (data (i32.const 1112) "\01\00\00\00(\00\00\00A\00l\00l\00o\00c\00a\00t\00i\00o\00n\00 \00t\00o\00o\00 \00l\00a\00r\00g\00e")
  (data (i32.const 1164) ",")
  (data (i32.const 1176) "\01\00\00\00\0e\00\00\00s\00i\00m\00d\00.\00t\00s")
+ (export "test_vars_i8x16_partial" (func $simd/test_vars_i8x16_partial))
+ (export "test_vars_i8x16_full" (func $simd/test_vars_i8x16_full))
+ (export "test_vars_i16x8_partial" (func $simd/test_vars_i16x8_partial))
+ (export "test_vars_i16x8_full" (func $simd/test_vars_i16x8_full))
+ (export "test_vars_i32x4_partial" (func $simd/test_vars_i32x4_partial))
+ (export "test_vars_i32x4_full" (func $simd/test_vars_i32x4_full))
+ (export "test_vars_i64x2_partial" (func $simd/test_vars_i64x2_partial))
+ (export "test_vars_i64x2_full" (func $simd/test_vars_i64x2_full))
+ (export "test_vars_f32x4_partial" (func $simd/test_vars_f32x4_partial))
+ (export "test_vars_f32x4_full" (func $simd/test_vars_f32x4_full))
+ (export "test_vars_f64x2_partial" (func $simd/test_vars_f64x2_partial))
+ (export "test_vars_f64x2_full" (func $simd/test_vars_f64x2_full))
  (export "memory" (memory $0))
  (start $~start)
  (func $~lib/rt/tlsf/removeBlock (param $0 i32) (param $1 i32)
@@ -975,6 +997,136 @@
   local.get $1
   call $~lib/rt/tlsf/insertBlock
  )
+ (func $simd/test_vars_i8x16_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x03000100 0x07000504 0x0b0a0908 0x000e0d0c
+  local.get $0
+  i8x16.replace_lane 2
+  local.get $1
+  i8x16.replace_lane 6
+  local.get $2
+  i8x16.replace_lane 15
+ )
+ (func $simd/test_vars_i8x16_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (param $4 i32) (param $5 i32) (param $6 i32) (param $7 i32) (param $8 i32) (param $9 i32) (param $10 i32) (param $11 i32) (param $12 i32) (param $13 i32) (param $14 i32) (param $15 i32) (result v128)
+  local.get $0
+  i8x16.splat
+  local.get $1
+  i8x16.replace_lane 1
+  local.get $2
+  i8x16.replace_lane 2
+  local.get $3
+  i8x16.replace_lane 3
+  local.get $4
+  i8x16.replace_lane 4
+  local.get $5
+  i8x16.replace_lane 5
+  local.get $6
+  i8x16.replace_lane 6
+  local.get $7
+  i8x16.replace_lane 7
+  local.get $8
+  i8x16.replace_lane 8
+  local.get $9
+  i8x16.replace_lane 9
+  local.get $10
+  i8x16.replace_lane 10
+  local.get $11
+  i8x16.replace_lane 11
+  local.get $12
+  i8x16.replace_lane 12
+  local.get $13
+  i8x16.replace_lane 13
+  local.get $14
+  i8x16.replace_lane 14
+  local.get $15
+  i8x16.replace_lane 15
+ )
+ (func $simd/test_vars_i16x8_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x00010000 0x00030000 0x00050000 0x00000006
+  local.get $0
+  i16x8.replace_lane 2
+  local.get $1
+  i16x8.replace_lane 4
+  local.get $2
+  i16x8.replace_lane 7
+ )
+ (func $simd/test_vars_i16x8_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (param $4 i32) (param $5 i32) (param $6 i32) (param $7 i32) (result v128)
+  local.get $0
+  i16x8.splat
+  local.get $1
+  i16x8.replace_lane 1
+  local.get $2
+  i16x8.replace_lane 2
+  local.get $3
+  i16x8.replace_lane 3
+  local.get $4
+  i16x8.replace_lane 4
+  local.get $5
+  i16x8.replace_lane 5
+  local.get $6
+  i16x8.replace_lane 6
+  local.get $7
+  i16x8.replace_lane 7
+ )
+ (func $simd/test_vars_i32x4_partial (param $0 i32) (param $1 i32) (param $2 i32) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  i32x4.replace_lane 1
+  local.get $1
+  i32x4.replace_lane 2
+  local.get $2
+  i32x4.replace_lane 3
+ )
+ (func $simd/test_vars_i32x4_full (param $0 i32) (param $1 i32) (param $2 i32) (param $3 i32) (result v128)
+  local.get $0
+  i32x4.splat
+  local.get $1
+  i32x4.replace_lane 1
+  local.get $2
+  i32x4.replace_lane 2
+  local.get $3
+  i32x4.replace_lane 3
+ )
+ (func $simd/test_vars_i64x2_partial (param $0 i64) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  i64x2.replace_lane 1
+ )
+ (func $simd/test_vars_i64x2_full (param $0 i64) (param $1 i64) (result v128)
+  local.get $0
+  i64x2.splat
+  local.get $1
+  i64x2.replace_lane 1
+ )
+ (func $simd/test_vars_f32x4_partial (param $0 f32) (param $1 f32) (param $2 f32) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  f32x4.replace_lane 1
+  local.get $1
+  f32x4.replace_lane 2
+  local.get $2
+  f32x4.replace_lane 3
+ )
+ (func $simd/test_vars_f32x4_full (param $0 f32) (param $1 f32) (param $2 f32) (param $3 f32) (result v128)
+  local.get $0
+  f32x4.splat
+  local.get $1
+  f32x4.replace_lane 1
+  local.get $2
+  f32x4.replace_lane 2
+  local.get $3
+  f32x4.replace_lane 3
+ )
+ (func $simd/test_vars_f64x2_partial (param $0 f64) (result v128)
+  v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000
+  local.get $0
+  f64x2.replace_lane 1
+ )
+ (func $simd/test_vars_f64x2_full (param $0 f64) (param $1 f64) (result v128)
+  local.get $0
+  f64x2.splat
+  local.get $1
+  f64x2.replace_lane 1
+ )
  (func $~start
   (local $0 i32)
   global.get $~lib/rt/tlsf/ROOT
diff --git a/tests/compiler/simd.ts b/tests/compiler/simd.ts
index 7abe0e8c82..857aa280a7 100644
--- a/tests/compiler/simd.ts
+++ b/tests/compiler/simd.ts
@@ -703,6 +703,62 @@ function test_const(): v128 {
   return one;                 // should not inline
 }
 
+export function test_vars_i8x16_partial(a: i8, b: i8, c: i8): v128 {
+  return i8x16(0, 1, a, 3, 4, 5, b, 7, 8, 9, 10, 11, 12, 13, 14, c);
+}
+
+export function test_vars_i8x16_full(
+  a: i8, b: i8, c: i8, d: i8,
+  e: i8, f: i8, g: i8, h: i8,
+  i: i8, k: i8, l: i8, m: i8,
+  n: i8, o: i8, p: i8, q: i8
+): v128 {
+  return i8x16(a, b, c, d, e, f, g, h, i, k, l, m, n, o, p, q);
+}
+
+export function test_vars_i16x8_partial(a: i16, b: i16, c: i16): v128 {
+  return i16x8(0, 1, a, 3, b, 5, 6, c);
+}
+
+export function test_vars_i16x8_full(
+  a: i16, b: i16, c: i16, d: i16,
+  e: i16, f: i16, g: i16, h: i16
+): v128 {
+  return i16x8(a, b, c, d, e, f, g, h);
+}
+
+export function test_vars_i32x4_partial(a: i32, b: i32, c: i32): v128 {
+  return i32x4(0, a, b, c);
+}
+
+export function test_vars_i32x4_full(a: i32, b: i32, c: i32, d: i32): v128 {
+  return i32x4(a, b, c, d);
+}
+
+export function test_vars_i64x2_partial(a: i64): v128 {
+  return i64x2(0, a);
+}
+
+export function test_vars_i64x2_full(a: i64, b: i64): v128 {
+  return i64x2(a, b);
+}
+
+export function test_vars_f32x4_partial(a: f32, b: f32, c: f32): v128 {
+  return f32x4(0, a, b, c);
+}
+
+export function test_vars_f32x4_full(a: f32, b: f32, c: f32, d: f32): v128 {
+  return f32x4(a, b, c, d);
+}
+
+export function test_vars_f64x2_partial(a: f64): v128 {
+  return f64x2(0, a);
+}
+
+export function test_vars_f64x2_full(a: f64, b: f64): v128 {
+  return f64x2(a, b);
+}
+
 if (ASC_FEATURE_SIMD) {
   test_v128();
   test_i8x16();