Add legalization for 0-sized arrays. (#7327)

* Add legalization for 0-sized arrays.

* Allow 0-sized arrays in the front-end.

* More tests.

* Add `Conditional<T, hasValue>` type to core module.

* Update toc.

* Fix wording.

* Update test.

3 files changed, 159 insertions, 0 deletions

diff --git a/tests/language-feature/0-array-1.slang b/tests/language-feature/0-array-1.slang
new file mode 100644
index 000000000..327f71444
--- /dev/null
+++ b/tests/language-feature/0-array-1.slang
@@ -0,0 +1,31 @@
+//TEST:SIMPLE(filecheck=SPV): -target spirv
+//TEST:SIMPLE(filecheck=HLSL): -target hlsl -profile cs_6_0 -entry computeMain
+
+struct MyData
+{
+    int a[0][0][0];
+}
+
+uniform MyData* myData;
+uniform int * output;
+
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    // These are all ill-formed, but we want to still ensure our backend
+    // can handle them gracefully without crashing.
+    // In actual user code, any access to 0-sized arrays should be protected
+    // by a `if` statement that checks the size before accessing.
+    // The condition would then evaluate to false and causing all the accessing
+    // code to be optimized out.
+    InterlockedAdd(myData.a[0][0][0], 1);
+    myData.a[0][0][0] += 1;
+    output[0] = myData.a[0][0][0];
+}
+
+//SPV: OpEntryPoint
+//SPV-NOT: OpAtomic
+//SPV-NOT: OpStore
+//SPV-NOT: OpLoad
+
+//HLSL: computeMain
diff --git a/tests/language-feature/0-array.slang b/tests/language-feature/0-array.slang
new file mode 100644
index 000000000..7379faace
--- /dev/null
+++ b/tests/language-feature/0-array.slang
@@ -0,0 +1,64 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK):
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -vk
+
+interface IVertex
+{
+    property float3 position{get;}
+    property Optional<float3> normal{get;}
+    property Optional<float3> color{get;}
+}
+
+struct Vertex<bool hasNormal, bool hasColor> : IVertex
+{
+    private float3 m_position;
+    private float3 m_normal[hasNormal];
+    private float3 m_color[hasColor];
+
+    __init(float3 position, float3 normal, float3 color)
+    {
+        m_position = position;
+        if (hasNormal) m_normal[0] = normal;
+        if (hasColor) m_color[0] = color;
+    }
+
+    property float3 position
+    {
+        get { return m_position; }
+    }
+    property Optional<float3> normal
+    {
+        get { if (hasNormal) return m_normal[0]; else return none; }
+    }
+    property Optional<float3> color
+    {
+        get { if (hasColor) return m_color[0]; else return none; }
+    }
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+void test<V:IVertex>(V vert)
+{
+    // CHECK: 0
+    // CHECK: 0
+    // CHECK: 1
+    // CHECK: 3
+    if (let normal = vert.normal)
+    {
+         outputBuffer[0] = 1;
+         outputBuffer[1] = (int)normal.x;
+    }
+
+    if (let color = vert.color)
+    {
+        outputBuffer[2] = 1;
+        outputBuffer[3] = (int)color.x;
+    }
+}
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    test<Vertex<false, true>>(Vertex<false, true>(1.0, 2.0, 3.0));
+}
\ No newline at end of file
diff --git a/tests/language-feature/cond-field.slang b/tests/language-feature/cond-field.slang
new file mode 100644
index 000000000..5e9f4a06e
--- /dev/null
+++ b/tests/language-feature/cond-field.slang
@@ -0,0 +1,64 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK):
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -vk
+
+interface IVertex
+{
+    property float3 position{get;}
+    property Optional<float3> normal{get;}
+    property Optional<float3> color{get;}
+}
+
+struct Vertex<bool hasNormal, bool hasColor> : IVertex
+{
+    private float3 m_position;
+    private Conditional<float3, hasNormal> m_normal;
+    private Conditional<float3, hasColor> m_color;
+
+    __init(float3 position, float3 normal, float3 color)
+    {
+        m_position = position;
+        m_normal = normal;
+        m_color = color;
+    }
+
+    property float3 position
+    {
+        get { return m_position; }
+    }
+    property Optional<float3> normal
+    {
+        get { return m_normal; }
+    }
+    property Optional<float3> color
+    {
+        get { return m_color; }
+    }
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+void test<V:IVertex>(V vert)
+{
+    // CHECK: 0
+    // CHECK: 0
+    // CHECK: 1
+    // CHECK: 3
+    if (let normal = vert.normal)
+    {
+         outputBuffer[0] = 1;
+         outputBuffer[1] = (int)normal.x;
+    }
+
+    if (let color = vert.color)
+    {
+        outputBuffer[2] = 1;
+        outputBuffer[3] = (int)color.x;
+    }
+}
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    test<Vertex<false, true>>(Vertex<false, true>(1.0, 2.0, 3.0));
+}
\ No newline at end of file