Fix min precision store widening: scope to ByteAddressBuffer only

The store widening for min precision types was applying to both
RawBufferStore (scalar) and RawBufferVectorStore (vector). This
broke StructuredBuffer stores (struct_buf3.hlsl) because it replaced
the correct sext/zext from TranslateMinPrecisionRawBuffer with a
blanket sext, losing signedness info for min16uint.

Scope the RawBufferStore widening to RawBuffer (ByteAddressBuffer)
only. StructuredBuffer scalar stores are correctly handled by the
later TranslateMinPrecisionRawBuffer pass in DxilGenerationPass,
which has signedness info from struct type annotations.

ByteAddressBuffer scalar stores still need widening here because
the later pass crashes on non-struct resource types (cast<StructType>
on ByteAddressBuffer's i32 inner element).

Co-authored-by: Copilot <[email protected]>

Author: alsepkow

lib/HLSL/HLOperationLower.cpp

@@ -4603,8 +4603,14 @@ void TranslateStore(DxilResource::Kind RK, Value *handle, Value *val,
   }
 
   // Min precision alloc size is 32-bit; widen to match store intrinsic.
-  if (opcode == OP::OpCode::RawBufferStore ||
-      opcode == OP::OpCode::RawBufferVectorStore) {
+  // StructuredBuffer scalar stores are handled by
+  // TranslateMinPrecisionRawBuffer in DxilGenerationPass, which has signedness
+  // info from struct annotations. ByteAddressBuffer (RawBuffer) scalar stores
+  // must be widened here because that later pass crashes on non-struct resource
+  // types (cast<StructType> fail).
+  if (opcode == OP::OpCode::RawBufferVectorStore ||
+      (opcode == OP::OpCode::RawBufferStore &&
+       RK == DxilResource::Kind::RawBuffer)) {
     const DataLayout &DL =
         OP->GetModule()->GetHLModule().GetModule()->getDataLayout();
     Type *WideTy = widenMinPrecisionType(Ty, Builder.getContext(), DL);