tint: Add end-to-end tests for expressions using f16 types

This patch add DXC compile flag "-enable-16bit-types" and change profile
to SM6.2 when validating generated HLSL using DXC if f16 extension is
enabled in the WGSL program.
The patch add Tint end-to-end test cases for expressions using f16 type,
including constructor, binary operator, splat, zero-init, and others.
Testcases that use f16 types in uniform or storage buffer are SKIPped,
because such usage is not implemented yet.

Bug: tint:1473, tint:1502
Change-Id: I481ab3d12cbb822f11ef85ba807bca3f9770089b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96252
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@chromium.org>
Commit-Queue: Zhaoming Jiang <zhaoming.jiang@intel.com>

test/tint/expressions/zero_init/array/f16.wgsl

@@ -0,0 +1,4 @@
+enable f16;
+fn f() {
+    var v = array<f16, 4>();
+}

test/tint/expressions/zero_init/array/f16.wgsl.expected.dxc.hlsl

@@ -0,0 +1,8 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void f() {
+  float16_t v[4] = (float16_t[4])0;
+}

test/tint/expressions/zero_init/array/f16.wgsl.expected.fxc.hlsl

@@ -0,0 +1,14 @@
+SKIP: FAILED
+
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void f() {
+  float16_t v[4] = (float16_t[4])0;
+}
+FXC validation failure:
+D:\Projects\RampUp\dawn\test\tint\expressions\Shader@0x000001C7D06B43D0(7,3-11): error X3000: unrecognized identifier 'float16_t'
+D:\Projects\RampUp\dawn\test\tint\expressions\Shader@0x000001C7D06B43D0(7,13): error X3000: unrecognized identifier 'v'
+

test/tint/expressions/zero_init/array/f16.wgsl.expected.glsl

@@ -0,0 +1,11 @@
+#version 310 es
+#extension GL_AMD_gpu_shader_half_float : require
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void unused_entry_point() {
+  return;
+}
+void f() {
+  float16_t v[4] = float16_t[4](0.0hf, 0.0hf, 0.0hf, 0.0hf);
+}
+

test/tint/expressions/zero_init/array/f16.wgsl.expected.msl

@@ -0,0 +1,20 @@
+#include <metal_stdlib>
+
+using namespace metal;
+
+template<typename T, size_t N>
+struct tint_array {
+    const constant T& operator[](size_t i) const constant { return elements[i]; }
+    device T& operator[](size_t i) device { return elements[i]; }
+    const device T& operator[](size_t i) const device { return elements[i]; }
+    thread T& operator[](size_t i) thread { return elements[i]; }
+    const thread T& operator[](size_t i) const thread { return elements[i]; }
+    threadgroup T& operator[](size_t i) threadgroup { return elements[i]; }
+    const threadgroup T& operator[](size_t i) const threadgroup { return elements[i]; }
+    T elements[N];
+};
+
+void f() {
+  tint_array<half, 4> v = tint_array<half, 4>{};
+}
+

test/tint/expressions/zero_init/array/f16.wgsl.expected.spvasm

@@ -0,0 +1,35 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 14
+; Schema: 0
+               OpCapability Shader
+               OpCapability Float16
+               OpCapability UniformAndStorageBuffer16BitAccess
+               OpCapability StorageBuffer16BitAccess
+               OpCapability StorageInputOutput16
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
+               OpExecutionMode %unused_entry_point LocalSize 1 1 1
+               OpName %unused_entry_point "unused_entry_point"
+               OpName %f "f"
+               OpName %v "v"
+               OpDecorate %_arr_half_uint_4 ArrayStride 2
+       %void = OpTypeVoid
+          %1 = OpTypeFunction %void
+       %half = OpTypeFloat 16
+       %uint = OpTypeInt 32 0
+     %uint_4 = OpConstant %uint 4
+%_arr_half_uint_4 = OpTypeArray %half %uint_4
+         %11 = OpConstantNull %_arr_half_uint_4
+%_ptr_Function__arr_half_uint_4 = OpTypePointer Function %_arr_half_uint_4
+%unused_entry_point = OpFunction %void None %1
+          %4 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %1
+          %6 = OpLabel
+          %v = OpVariable %_ptr_Function__arr_half_uint_4 Function %11
+               OpStore %v %11
+               OpReturn
+               OpFunctionEnd

test/tint/expressions/zero_init/array/f16.wgsl.expected.wgsl

@@ -0,0 +1,5 @@
+enable f16;
+
+fn f() {
+  var v = array<f16, 4>();
+}