[clang] [Clang][CodeGen][CUDA] Add missing null-check assertions in CGCUDARuntime (PR #181167)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: UnknownUser (Z3rox-dev)

<details>
<summary>Changes</summary>

## Summary

Add defensive `assert` checks for all `getAs<>()` calls in `CGCUDARuntime.cpp` that were previously dereferenced without null verification.

## Details

The file had **8 unchecked `getAs<>()`** calls across `emitGetParamBuf()` and `EmitCUDADeviceKernelCallExpr()`, including chained dereferences like:

```cpp
E->getCallee()->getType()->getAs<PointerType>()->getPointeeType();
```

where a null return from `getAs<PointerType>()` would cause an immediate crash with no diagnostic.

### Changes:
- Added `assert()` null checks for all `getAs<PointerType>()` and `getAs<FunctionProtoType>()` results
- Eliminated **3 redundant `getAs<>()` calls** by caching results in local variables (`KernelPT`, `KernelFPT`, `LaunchPT`, `LaunchFPT`)
- Broke chained dereferences into separate, checked steps

### Motivation:
While Sema validation currently prevents these types from being null in practice, this change:
1. Follows the established defensive coding pattern used elsewhere in CodeGen (e.g., `CGExprScalar.cpp`, `CGObjCMac.cpp`)
2. Provides executable documentation of the implicit type contract
3. Improves debuggability in assertion-enabled builds
4. Makes the code more resilient to future refactoring that might alter Sema guarantees

**NFC** (no functional change in release builds — asserts are compiled out).

## Testing
- `check-clang-codegen-cuda`: **75/75 passed**
- `check-clang-sema-cuda`: **99/99 passed**
- `clang-format`: clean


---
Full diff: https://github.com/llvm/llvm-project/pull/181167.diff


1 Files Affected:

- (modified) clang/lib/CodeGen/CGCUDARuntime.cpp (+20-14) 


``````````diff
diff --git a/clang/lib/CodeGen/CGCUDARuntime.cpp b/clang/lib/CodeGen/CGCUDARuntime.cpp
index 9c831b26c3a7b..545233e4f1221 100644
--- a/clang/lib/CodeGen/CGCUDARuntime.cpp
+++ b/clang/lib/CodeGen/CGCUDARuntime.cpp
@@ -27,6 +27,8 @@ static llvm::Value *emitGetParamBuf(CodeGenFunction &CGF,
   auto *GetParamBuf = CGF.getContext().getcudaGetParameterBufferDecl();
   const FunctionProtoType *GetParamBufProto =
       GetParamBuf->getType()->getAs<FunctionProtoType>();
+  assert(GetParamBufProto &&
+         "cudaGetParameterBuffer must have function proto type");
 
   DeclRefExpr *DRE = DeclRefExpr::Create(
       CGF.getContext(), {}, {}, GetParamBuf,
@@ -43,8 +45,10 @@ static llvm::Value *emitGetParamBuf(CodeGenFunction &CGF,
            CGF.getContext().getSizeType());
   // Calculate parameter sizes.
   const PointerType *PT = E->getCallee()->getType()->getAs<PointerType>();
+  assert(PT && "CUDA kernel callee must be a pointer type");
   const FunctionProtoType *FTP =
       PT->getPointeeType()->getAs<FunctionProtoType>();
+  assert(FTP && "CUDA kernel callee must be a function proto type");
   CharUnits Offset = CharUnits::Zero();
   for (auto ArgTy : FTP->getParamTypes()) {
     auto TInfo = CGF.CGM.getContext().getTypeInfoInChars(ArgTy);
@@ -79,14 +83,16 @@ RValue CGCUDARuntime::EmitCUDADeviceKernelCallExpr(
   eval.begin(CGF);
   CGF.EmitBlock(ConfigOKBlock);
 
-  QualType KernelCalleeFuncTy =
-      E->getCallee()->getType()->getAs<PointerType>()->getPointeeType();
+  const auto *KernelPT = E->getCallee()->getType()->getAs<PointerType>();
+  assert(KernelPT && "CUDA kernel callee must be a pointer type");
+  QualType KernelCalleeFuncTy = KernelPT->getPointeeType();
   CGCallee KernelCallee = CGF.EmitCallee(E->getCallee());
   // Emit kernel arguments.
   CallArgList KernelCallArgs;
-  CGF.EmitCallArgs(KernelCallArgs,
-                   KernelCalleeFuncTy->getAs<FunctionProtoType>(),
-                   E->arguments(), E->getDirectCallee());
+  const auto *KernelFPT = KernelCalleeFuncTy->getAs<FunctionProtoType>();
+  assert(KernelFPT && "CUDA kernel callee must be a function proto type");
+  CGF.EmitCallArgs(KernelCallArgs, KernelFPT, E->arguments(),
+                   E->getDirectCallee());
   // Copy emitted kernel arguments into that parameter buffer.
   RawAddress CfgBase(Config, CGM.Int8Ty,
                      /*Alignment=*/CharUnits::fromQuantity(64));
@@ -101,22 +107,22 @@ RValue CGCUDARuntime::EmitCUDADeviceKernelCallExpr(
   }
   // Make `cudaLaunchDevice` call, i.e. E->getConfig().
   const CallExpr *LaunchCall = E->getConfig();
-  QualType LaunchCalleeFuncTy = LaunchCall->getCallee()
-                                    ->getType()
-                                    ->getAs<PointerType>()
-                                    ->getPointeeType();
+  const auto *LaunchPT =
+      LaunchCall->getCallee()->getType()->getAs<PointerType>();
+  assert(LaunchPT && "CUDA launch callee must be a pointer type");
+  QualType LaunchCalleeFuncTy = LaunchPT->getPointeeType();
   CGCallee LaunchCallee = CGF.EmitCallee(LaunchCall->getCallee());
   CallArgList LaunchCallArgs;
-  CGF.EmitCallArgs(LaunchCallArgs,
-                   LaunchCalleeFuncTy->getAs<FunctionProtoType>(),
-                   LaunchCall->arguments(), LaunchCall->getDirectCallee());
+  const auto *LaunchFPT = LaunchCalleeFuncTy->getAs<FunctionProtoType>();
+  assert(LaunchFPT && "CUDA launch callee must be a function proto type");
+  CGF.EmitCallArgs(LaunchCallArgs, LaunchFPT, LaunchCall->arguments(),
+                   LaunchCall->getDirectCallee());
   // Replace func and paramterbuffer arguments.
   LaunchCallArgs[0] = CallArg(RValue::get(KernelCallee.getFunctionPointer()),
                               CGM.getContext().VoidPtrTy);
   LaunchCallArgs[1] = CallArg(RValue::get(Config), CGM.getContext().VoidPtrTy);
   const CGFunctionInfo &LaunchCallInfo = CGM.getTypes().arrangeFreeFunctionCall(
-      LaunchCallArgs, LaunchCalleeFuncTy->getAs<FunctionProtoType>(),
-      /*ChainCall=*/false);
+      LaunchCallArgs, LaunchFPT, /*ChainCall=*/false);
   CGF.EmitCall(LaunchCallInfo, LaunchCallee, ReturnValue, LaunchCallArgs,
                CallOrInvoke,
                /*IsMustTail=*/false, E->getExprLoc());

``````````

</details>


https://github.com/llvm/llvm-project/pull/181167