Remove OptimizeNone attribute from optnone builtins after clang

compilation.

Author: aratajew

IGC/AdaptorCommon/ProcessFuncAttributes.cpp

@@ -413,20 +413,27 @@ bool ProcessFuncAttributes::runOnModule(Module& M)
         if (isKernel)
             continue;
 
+        // OptNone builtins are special versions of builtins assuring that all
+        // theirs parameters are constant values.
+        if(isOptNoneBuiltin(F->getName()))
+        {
+            // OptimizeNone attribute was only required to prevent clang optimizations.
+            // We can remove it now to unblock IGC optimizations.
+            F->removeFnAttr(llvm::Attribute::OptimizeNone);
+            // Treat optnone builtins as stackcalls to avoid kernel bloat.
+            pCtx->m_enableStackCall = true;
+            F->addFnAttr("visaStackCall");
+            continue;
+        }
+
         // Flag for function calls where alwaysinline must be true
         bool mustAlwaysInline = false;
 
         // Add always attribtue if function is a builtin
         if (F->hasFnAttribute(llvm::Attribute::Builtin) ||
             F->getName().startswith(spv::kLLVMName::builtinPrefix))
         {
-            if(isOptNoneBuiltin(F->getName()))
-            {
-                pCtx->m_enableStackCall = true;
-                F->addFnAttr("visaStackCall");
-            }
-            else
-                mustAlwaysInline = true;
+            mustAlwaysInline = true;
         }
         // inline all OCL math functions if __FastRelaxedMath is set
         else if (fastMathFunct.find(F) != fastMathFunct.end())