From 110d15b61ac5d76da001d412eaa4be07f3cd8f4d Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 19 Jun 2020 11:19:51 -0700
Subject: Dynamic dispatch for static member functions of associatedtypes.
 (#1404)

---
 source/slang/slang-emit-c-like.cpp                 | 13 ++----
 source/slang/slang-emit-cpp.cpp                    | 21 +++++++--
 tests/compute/dynamic-dispatch-2.slang             | 53 ++++++++++++++++++++++
 .../compute/dynamic-dispatch-2.slang.expected.txt  |  4 ++
 4 files changed, 78 insertions(+), 13 deletions(-)
 create mode 100644 tests/compute/dynamic-dispatch-2.slang
 create mode 100644 tests/compute/dynamic-dispatch-2.slang.expected.txt

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index 6c004c84c..3438fd3f4 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -237,18 +237,15 @@ List<IRWitnessTableEntry*> CLikeSourceEmitter::getSortedWitnessTableEntries(IRWi
     for (UInt i = 0; i < interfaceType->getOperandCount(); i++)
     {
         auto reqKey = cast<IRStructKey>(interfaceType->getOperand(i));
-        bool matchingEntryFound = false;
         IRWitnessTableEntry* entry = nullptr;
         if (witnessTableEntryDictionary.TryGetValue(reqKey, entry))
         {
-            if (entry->requirementKey.get() == reqKey)
-            {
-                matchingEntryFound = true;
-                sortedWitnessTableEntries.add(entry);
-                break;
-            }
+            sortedWitnessTableEntries.add(entry);
+        }
+        else
+        {
+            SLANG_UNREACHABLE("interface requirement key not found in witness table.");
         }
-        SLANG_ASSERT(matchingEntryFound);
     }
     return sortedWitnessTableEntries;
 }
diff --git a/source/slang/slang-emit-cpp.cpp b/source/slang/slang-emit-cpp.cpp
index accb290fa..4a59f4cf9 100644
--- a/source/slang/slang-emit-cpp.cpp
+++ b/source/slang/slang-emit-cpp.cpp
@@ -1711,6 +1711,15 @@ void CPPSourceEmitter::_emitWitnessTableDefinitions()
                 m_writer->emit("&KernelContext::");
                 m_writer->emit(_getWitnessTableWrapperFuncName(funcVal));
             }
+            else if (auto witnessTableVal = as<IRWitnessTable>(entry->getSatisfyingVal()))
+            {
+                if (!isFirstEntry)
+                    m_writer->emit(",\n");
+                else
+                    isFirstEntry = false;
+                m_writer->emit("&");
+                m_writer->emit(getName(witnessTableVal));
+            }
             else
             {
                 // TODO: handle other witness table entry types.
@@ -1745,16 +1754,11 @@ void CPPSourceEmitter::_maybeEmitWitnessTableTypeDefinition(
     emitSimpleType(interfaceType);
     m_writer->emit("\n{\n");
     m_writer->indent();
-    bool isFirstEntry = true;
     for (Index i = 0; i < sortedWitnessTableEntries.getCount(); i++)
     {
         auto entry = sortedWitnessTableEntries[i];
         if (auto funcVal = as<IRFunc>(entry->satisfyingVal.get()))
         {
-            if (!isFirstEntry)
-                m_writer->emit(",\n");
-            else
-                isFirstEntry = false;
             emitType(funcVal->getResultType());
             m_writer->emit(" (KernelContext::*");
             m_writer->emit(getName(entry->requirementKey.get()));
@@ -1777,6 +1781,13 @@ void CPPSourceEmitter::_maybeEmitWitnessTableTypeDefinition(
             }
             m_writer->emit(");\n");
         }
+        else if (auto witnessTableVal = as<IRWitnessTable>(entry->getSatisfyingVal()))
+        {
+            emitType(as<IRType>(witnessTableVal->getOperand(0)));
+            m_writer->emit("* ");
+            m_writer->emit(getName(entry->requirementKey.get()));
+            m_writer->emit(";\n");
+        }
         else
         {
             // TODO: handle other witness table entry types.
diff --git a/tests/compute/dynamic-dispatch-2.slang b/tests/compute/dynamic-dispatch-2.slang
new file mode 100644
index 000000000..ade8aeb84
--- /dev/null
+++ b/tests/compute/dynamic-dispatch-2.slang
@@ -0,0 +1,53 @@
+//TEST(compute):COMPARE_COMPUTE:-cpu -xslang -allow-dynamic-code
+
+// Test dynamic dispatch code gen for static member functions
+// of associated type.
+
+interface IAssoc
+{
+    int get();
+    static int getBase();
+}
+interface IInterface
+{
+    associatedtype Assoc : IAssoc;
+	int Compute(int inVal);
+    Assoc getAssoc();
+};
+
+int GenericCompute<T:IInterface>(T obj, int inVal)
+{
+	return obj.Compute(inVal) + T.Assoc.getBase();
+}
+
+struct Impl : IInterface
+{
+    struct Assoc : IAssoc
+    {
+        int val;
+        int get() { return val; }
+        static int getBase() { return -1; }
+    };
+    int base;
+	int Compute(int inVal) { return base + inVal * inVal; }
+    Assoc getAssoc() { Assoc rs; rs.val = 1; return rs; }
+};
+
+int test(int inVal)
+{
+    Impl obj;
+    obj.base = 1;
+	return GenericCompute<Impl>(obj, inVal);
+}
+
+//TEST_INPUT:ubuffer(data=[0 1 2 3], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer : register(u0);
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+	uint tid = dispatchThreadID.x;
+	int inVal = outputBuffer[tid];
+	int outVal = test(inVal);
+	outputBuffer[tid] = outVal;
+}
diff --git a/tests/compute/dynamic-dispatch-2.slang.expected.txt b/tests/compute/dynamic-dispatch-2.slang.expected.txt
new file mode 100644
index 000000000..c9fa0697e
--- /dev/null
+++ b/tests/compute/dynamic-dispatch-2.slang.expected.txt
@@ -0,0 +1,4 @@
+0
+1
+4
+9
-- 
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