[HLSL][SPIRV] Add convergence tokens to entry point wrapper

Inlining currently assumes that either all function use controled
convergence or none of them do. This is why we need to have the entry
point wrapper use controled convergence.

https://github.com/llvm/llvm-project/blob/c85611e8583e6392d56075ebdfa60893b6284813/llvm/lib/Transforms/Utils/InlineFunction.cpp#L2431-L2439

Author: s-perron

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -399,6 +399,17 @@ void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
   BasicBlock *BB = BasicBlock::Create(Ctx, "entry", EntryFn);
   IRBuilder<> B(BB);
   llvm::SmallVector<Value *> Args;
+
+  SmallVector<OperandBundleDef, 1> OB;
+  if (CGM.shouldEmitConvergenceTokens()) {
+    assert(EntryFn->isConvergent());
+    llvm::Value *
+        I = B.CreateIntrinsic(llvm::Intrinsic::experimental_convergence_entry, {},
+                              {});
+    llvm::Value *bundleArgs[] = {I};
+    OB.emplace_back("convergencectrl", bundleArgs);
+  }
+
   // FIXME: support struct parameters where semantics are on members.
   // See: https://github.com/llvm/llvm-project/issues/57874
   unsigned SRetOffset = 0;
@@ -414,7 +425,7 @@ void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
     Args.push_back(emitInputSemantic(B, *PD, Param.getType()));
   }
 
-  CallInst *CI = B.CreateCall(FunctionCallee(Fn), Args);
+  CallInst *CI = B.CreateCall(FunctionCallee(Fn), Args, OB);
   CI->setCallingConv(Fn->getCallingConv());
   // FIXME: Handle codegen for return type semantics.
   // See: https://github.com/llvm/llvm-project/issues/57875
@@ -469,14 +480,21 @@ void CGHLSLRuntime::generateGlobalCtorDtorCalls() {
   for (auto &F : M.functions()) {
     if (!F.hasFnAttribute("hlsl.shader"))
       continue;
-    IRBuilder<> B(&F.getEntryBlock(), F.getEntryBlock().begin());
+    auto* Token = getConvergenceToken(F.getEntryBlock());
+    Instruction* IP = Token ? Token : &*F.getEntryBlock().begin();
+    IRBuilder<> B(IP);
+    std::vector<OperandBundleDef> OB;
+    if (Token) {
+      llvm::Value *bundleArgs[] = {Token};
+      OB.emplace_back("convergencectrl", bundleArgs);
+    }
     for (auto *Fn : CtorFns)
-      B.CreateCall(FunctionCallee(Fn));
+      B.CreateCall(FunctionCallee(Fn), {}, OB);
 
     // Insert global dtors before the terminator of the last instruction
     B.SetInsertPoint(F.back().getTerminator());
     for (auto *Fn : DtorFns)
-      B.CreateCall(FunctionCallee(Fn));
+      B.CreateCall(FunctionCallee(Fn), {}, OB);
   }
 
   // No need to keep global ctors/dtors for non-lib profile after call to
@@ -489,3 +507,18 @@ void CGHLSLRuntime::generateGlobalCtorDtorCalls() {
       GV->eraseFromParent();
   }
 }
+
+llvm::Instruction *CGHLSLRuntime::getConvergenceToken(BasicBlock &BB) {
+  if (!CGM.shouldEmitConvergenceTokens())
+    return nullptr;
+
+  auto E = BB.end();
+  for(auto I = BB.begin(); I != E; ++I) {
+    auto *II = dyn_cast<llvm::IntrinsicInst>(&*I);
+    if (II && llvm::isConvergenceControlIntrinsic(II->getIntrinsicID())) {
+      return II;
+    }
+  }
+  llvm_unreachable("Convergence token should have been emitted.");
+  return nullptr;
+}

clang/lib/CodeGen/CGHLSLRuntime.h

@@ -137,6 +137,7 @@ class CGHLSLRuntime {
 
   void emitEntryFunction(const FunctionDecl *FD, llvm::Function *Fn);
   void setHLSLFunctionAttributes(const FunctionDecl *FD, llvm::Function *Fn);
+  llvm::Instruction *getConvergenceToken(llvm::BasicBlock &BB);
 
 private:
   void addBufferResourceAnnotation(llvm::GlobalVariable *GV,

clang/test/CodeGenHLSL/convergence/entry.point.hlsl

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -triple spirv-pc-vulkan-compute -finclude-default-header -fnative-half-type -disable-llvm-passes -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: define void @main()
+// CHECK-NEXT: entry:
+// CHECK-NEXT: [[token:%[0-9]+]] = call token @llvm.experimental.convergence.entry()
+// CHECK-NEXT: call spir_func void @_Z4mainv() [ "convergencectrl"(token [[token]]) ]
+
+[numthreads(1,1,1)]
+void main() {
+}
+