Disable l-value coercion for ref types (#2960)

* Make lvalue coercion not work for ref, to stop problem with atomics (for GLSL output).

* Improve some comments.

2 files changed, 31 insertions, 0 deletions

diff --git a/tests/bugs/atomic-coerce.slang b/tests/bugs/atomic-coerce.slang
new file mode 100644
index 000000000..1e56a8d25
--- /dev/null
+++ b/tests/bugs/atomic-coerce.slang
@@ -0,0 +1,27 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj 
+//TEST(compute,vulkan):COMPARE_COMPUTE_EX:-vk -slang -compute -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 ], stride=4):out,name outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+groupshared uint gs_values[2];
+
+[shader("compute")]
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    int index = (int)dispatchThreadID.x;
+    
+    // Initialize first
+    if (index < 2)
+    {
+        gs_values[index] = 2;
+    }
+
+    GroupMemoryBarrierWithGroupSync();
+ 
+    // NOTE! We have to cast to uint, to make atomic work
+    InterlockedAdd(gs_values[index & 1], uint(index * index));
+           
+    outputBuffer[index] = gs_values[index & 1];
+}
diff --git a/tests/bugs/atomic-coerce.slang.expected.txt b/tests/bugs/atomic-coerce.slang.expected.txt
new file mode 100644
index 000000000..9f774a3a1
--- /dev/null
+++ b/tests/bugs/atomic-coerce.slang.expected.txt
@@ -0,0 +1,4 @@
+6
+C
+6
+C