[WebAssembly] Fix argument types in SIMD narrowing intrinsics

[tlively]

Summary

The builtins were updated to take signed parameters in 627a52695537, but the
intrinsics that use those builtins were not updated as well. The intrinsic test
did not catch this sign mismatch because it is only reported as an error under
-fno-lax-vector-conversions.

This commit fixes the type mismatch and adds -fno-lax-vector-conversions to the
test to catch similar problems in the future.

clang/lib/Headers/wasm_simd128.h

 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_i8x16_narrow_i16x8(v128_t __a, v128_t __b) {
   return (v128_t)__builtin_wasm_narrow_s_i8x16_i16x8((__i16x8)__a,
                                                      (__i16x8)__b);
 }
 
 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((__u16x8)__a,
-                                                     (__u16x8)__b);
+  return (v128_t)__builtin_wasm_narrow_u_i8x16_i16x8((__i16x8)__a,
+                                                     (__i16x8)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_i16x8_narrow_i32x4(v128_t __a, v128_t __b) {
   return (v128_t)__builtin_wasm_narrow_s_i16x8_i32x4((__i32x4)__a,
                                                      (__i32x4)__b);
 }
 
 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((__u32x4)__a,
-                                                     (__u32x4)__b);
+  return (v128_t)__builtin_wasm_narrow_u_i16x8_i32x4((__i32x4)__a,
+                                                     (__i32x4)__b);
 }
 
 static __inline__ v128_t __DEFAULT_FN_ATTRS
 wasm_i16x8_extend_low_i8x16(v128_t __a) {
   return (v128_t) __builtin_convertvector(
       (__i8x8){((__i8x16)__a)[0], ((__i8x16)__a)[1], ((__i8x16)__a)[2],
                ((__i8x16)__a)[3], ((__i8x16)__a)[4], ((__i8x16)__a)[5],
                ((__i8x16)__a)[6], ((__i8x16)__a)[7]},

clang/test/Headers/wasm.c

 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --force-update
 // REQUIRES: webassembly-registered-target, asserts
 
-// RUN: %clang %s -O2 -emit-llvm -S -o - -target wasm32-unknown-unknown -msimd128 -Wcast-qual -Werror | FileCheck %s
+// RUN: %clang %s -O2 -emit-llvm -S -o - -target wasm32-unknown-unknown -msimd128 -Wcast-qual -fno-lax-vector-conversions -Werror | FileCheck %s
 
 #include <wasm_simd128.h>
 
 // CHECK-LABEL: @test_v128_load(
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    [[__V_I:%.*]] = bitcast i8* [[MEM:%.*]] to <4 x i32>*
 // CHECK-NEXT:    [[TMP0:%.*]] = load <4 x i32>, <4 x i32>* [[__V_I]], align 1, !tbaa [[TBAA2:![0-9]+]]
 // CHECK-NEXT:    ret <4 x i32> [[TMP0]]