Improve performance when compiling small shaders. (#6396)

Improve performance when compiling small shaders.

Avoid copying witness table entries that are not getting used during linking.
Avoid copying auto-diff related decorations and derivative functions during linking, if the user modules doesn't use autodiff.
Cache operator overload resolution results on global session, so each new Session doesn't need to repetitively run through overload resolution from scratch.

1 files changed, 30 insertions, 0 deletions

diff --git a/source/slang/slang-ir-strip.cpp b/source/slang/slang-ir-strip.cpp
index e9fbbceb6..6c64bfca2 100644
--- a/source/slang/slang-ir-strip.cpp
+++ b/source/slang/slang-ir-strip.cpp
@@ -51,4 +51,34 @@ void stripFrontEndOnlyInstructions(IRModule* module, IRStripOptions const& optio
     _stripFrontEndOnlyInstructionsRec(module->getModuleInst(), options);
 }
 
+void stripImportedWitnessTable(IRModule* module)
+{
+    for (auto globalInst : module->getGlobalInsts())
+    {
+        auto inst = globalInst;
+        switch (globalInst->getOp())
+        {
+        case kIROp_Generic:
+            inst = findInnerMostGenericReturnVal(as<IRGeneric>(globalInst));
+            break;
+        case kIROp_WitnessTable:
+            break;
+        default:
+            continue;
+        }
+        if (inst->getOp() != kIROp_WitnessTable)
+            continue;
+        if (!globalInst->findDecoration<IRImportDecoration>())
+            continue;
+        IRInst* nextChild = nullptr;
+        for (auto child = inst->getFirstChild(); child;)
+        {
+            nextChild = child->getNextInst();
+            if (child->getOp() == kIROp_WitnessTable)
+                child->removeAndDeallocate();
+            child = nextChild;
+        }
+    }
+}
+
 } // namespace Slang