diff --git a/clang/lib/Headers/wasm_simd128.h b/clang/lib/Headers/wasm_simd128.h
--- a/clang/lib/Headers/wasm_simd128.h
+++ b/clang/lib/Headers/wasm_simd128.h
@@ -622,8 +622,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u8x16_add_saturate(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_add_saturate_u_i8x16((__i8x16)__a,
-                                                     (__i8x16)__b);
+  return (v128_t)__builtin_wasm_add_saturate_u_i8x16((__u8x16)__a,
+                                                     (__u8x16)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i8x16_sub(v128_t __a,
@@ -639,8 +639,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u8x16_sub_saturate(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_sub_saturate_u_i8x16((__i8x16)__a,
-                                                     (__i8x16)__b);
+  return (v128_t)__builtin_wasm_sub_saturate_u_i8x16((__u8x16)__a,
+                                                     (__u8x16)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i8x16_min(v128_t __a,
@@ -650,7 +650,7 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u8x16_min(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_min_u_i8x16((__i8x16)__a, (__i8x16)__b);
+  return (v128_t)__builtin_wasm_min_u_i8x16((__u8x16)__a, (__u8x16)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i8x16_max(v128_t __a,
@@ -660,12 +660,12 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u8x16_max(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_max_u_i8x16((__i8x16)__a, (__i8x16)__b);
+  return (v128_t)__builtin_wasm_max_u_i8x16((__u8x16)__a, (__u8x16)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u8x16_avgr(v128_t __a,
                                                             v128_t __b) {
-  return (v128_t)__builtin_wasm_avgr_u_i8x16((__i8x16)__a, (__i8x16)__b);
+  return (v128_t)__builtin_wasm_avgr_u_i8x16((__u8x16)__a, (__u8x16)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i16x8_abs(v128_t __a) {
@@ -712,8 +712,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u16x8_add_saturate(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_add_saturate_u_i16x8((__i16x8)__a,
-                                                     (__i16x8)__b);
+  return (v128_t)__builtin_wasm_add_saturate_u_i16x8((__u16x8)__a,
+                                                     (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i16x8_sub(v128_t __a,
@@ -729,8 +729,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u16x8_sub_saturate(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_sub_saturate_u_i16x8((__i16x8)__a,
-                                                     (__i16x8)__b);
+  return (v128_t)__builtin_wasm_sub_saturate_u_i16x8((__u16x8)__a,
+                                                     (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i16x8_mul(v128_t __a,
@@ -745,7 +745,7 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u16x8_min(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_min_u_i16x8((__i16x8)__a, (__i16x8)__b);
+  return (v128_t)__builtin_wasm_min_u_i16x8((__u16x8)__a, (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i16x8_max(v128_t __a,
@@ -755,12 +755,12 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u16x8_max(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_max_u_i16x8((__i16x8)__a, (__i16x8)__b);
+  return (v128_t)__builtin_wasm_max_u_i16x8((__u16x8)__a, (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u16x8_avgr(v128_t __a,
                                                             v128_t __b) {
-  return (v128_t)__builtin_wasm_avgr_u_i16x8((__i16x8)__a, (__i16x8)__b);
+  return (v128_t)__builtin_wasm_avgr_u_i16x8((__u16x8)__a, (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i32x4_abs(v128_t __a) {
@@ -816,7 +816,7 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u32x4_min(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_min_u_i32x4((__i32x4)__a, (__i32x4)__b);
+  return (v128_t)__builtin_wasm_min_u_i32x4((__u32x4)__a, (__u32x4)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i32x4_max(v128_t __a,
@@ -826,7 +826,7 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_u32x4_max(v128_t __a,
                                                            v128_t __b) {
-  return (v128_t)__builtin_wasm_max_u_i32x4((__i32x4)__a, (__i32x4)__b);
+  return (v128_t)__builtin_wasm_max_u_i32x4((__u32x4)__a, (__u32x4)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS wasm_i64x2_neg(v128_t __a) {
@@ -1077,8 +1077,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u8x16_narrow_i16x8(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_narrow_u_i8x16_i16x8((__i16x8)__a,
-                                                     (__i16x8)__b);
+  return (v128_t)__builtin_wasm_narrow_u_i8x16_i16x8((__u16x8)__a,
+                                                     (__u16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
@@ -1089,8 +1089,8 @@
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_u16x8_narrow_i32x4(v128_t __a, v128_t __b) {
-  return (v128_t)__builtin_wasm_narrow_u_i16x8_i32x4((__i32x4)__a,
-                                                     (__i32x4)__b);
+  return (v128_t)__builtin_wasm_narrow_u_i16x8_i32x4((__u32x4)__a,
+                                                     (__u32x4)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
diff --git a/clang/test/Headers/wasm.c b/clang/test/Headers/wasm.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Headers/wasm.c
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -target-feature +simd128 -fsyntax-only -ffreestanding %s -verify
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -target-feature +simd128 -fsyntax-only -ffreestanding -flax-vector-conversions=none %s -verify
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -target-feature +simd128 -fsyntax-only -ffreestanding -x c++ %s -verify
+// expected-no-diagnostics
+
+#if defined(__wasm__) && defined(__wasm_simd128__)
+
+#include <wasm_simd128.h>
+
+#endif
diff --git a/clang/test/Headers/wasm.cpp b/clang/test/Headers/wasm.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Headers/wasm.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -target-feature +simd128 -fsyntax-only -ffreestanding %s -verify
+// expected-no-diagnostics
+
+#if defined(__wasm__) && defined(__wasm_simd128__)
+
+extern "C++" {
+#include <wasm_simd128.h>
+}
+
+#endif