Specialize and SSA in a loop + better diagnostics on dynamic dispatch failure (#2396)

* Report diagnostic when dynamic dispatch failed instead of crashing.

* Specialize and SSA in a loop. Explicit specialization only interface.

Co-authored-by: Yong He <yhe@nvidia.com>

2 files changed, 46 insertions, 0 deletions

diff --git a/tests/bugs/specialize-existential-in-generic.slang b/tests/bugs/specialize-existential-in-generic.slang
new file mode 100644
index 000000000..31ef75512
--- /dev/null
+++ b/tests/bugs/specialize-existential-in-generic.slang
@@ -0,0 +1,42 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj
+
+[Specialize]
+interface IAssoc
+{
+    int getInner();
+}
+
+interface IFoo
+{
+    associatedtype Assoc : IAssoc;
+    Assoc getValue();
+}
+
+struct Impl : IFoo
+{
+    struct Assoc : IAssoc { int getInner() { return 1; } }
+    Assoc getValue() { Assoc r; return r; }
+}
+
+struct GenType<T : IFoo>
+{
+    T obj;
+    int doThing()
+    {
+        IAssoc soc = obj.getValue(); // "boxing" into an existential
+
+        // a specialized version of this function should call specialized method instead of going through dynamic dispatch.
+        return soc.getInner();
+    }
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=gOutputBuffer
+RWStructuredBuffer<int> gOutputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(int3 dispatchThreadID: SV_DispatchThreadID)
+{
+    int tid = dispatchThreadID.x;
+    GenType<Impl> val;
+    gOutputBuffer[tid] = val.doThing();
+}
\ No newline at end of file
diff --git a/tests/bugs/specialize-existential-in-generic.slang.expected.txt b/tests/bugs/specialize-existential-in-generic.slang.expected.txt
new file mode 100644
index 000000000..ef529012e
--- /dev/null
+++ b/tests/bugs/specialize-existential-in-generic.slang.expected.txt
@@ -0,0 +1,4 @@
+1
+1
+1
+1
\ No newline at end of file