[clang] 2bf4889 - [HIP] document difference with CUDA (#86838)

[via cfe-commits]

Author: Yaxun (Sam) Liu
Date: 2024-04-10T11:16:00-04:00
New Revision: 2bf48892ab0ce5d53126c7b114070bba18521501

URL: https://github.com/llvm/llvm-project/commit/2bf48892ab0ce5d53126c7b114070bba18521501
DIFF: https://github.com/llvm/llvm-project/commit/2bf48892ab0ce5d53126c7b114070bba18521501.diff

LOG: [HIP] document difference with CUDA (#86838)

Added: 
    

Modified: 
    clang/docs/HIPSupport.rst

Removed: 
    


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diff  --git a/clang/docs/HIPSupport.rst b/clang/docs/HIPSupport.rst
index 543c82cf902449..5ba84c2f670556 100644
--- a/clang/docs/HIPSupport.rst
+++ b/clang/docs/HIPSupport.rst
@@ -208,6 +208,20 @@ Host Code Compilation
 - These relocatable objects are then linked together.
 - Host code within a TU can call host functions and launch kernels from another TU.
 
+Syntax Difference with CUDA
+===========================
+
+Clang's front end, used for both CUDA and HIP programming models, shares the same parsing and semantic analysis mechanisms. This includes the resolution of overloads concerning device and host functions. While there exists a comprehensive documentation on the syntax 
diff erences between Clang and NVCC for CUDA at `Dialect Differences Between Clang and NVCC <https://llvm.org/docs/CompileCudaWithLLVM.html#dialect-
diff erences-between-clang-and-nvcc>`_, it is important to note that these 
diff erences also apply to HIP code compilation.
+
+Predefined Macros for Differentiation
+-------------------------------------
+
+To facilitate 
diff erentiation between HIP and CUDA code, as well as between device and host compilations within HIP, Clang defines specific macros:
+
+- ``__HIP__`` : This macro is defined only when compiling HIP code. It can be used to conditionally compile code specific to HIP, enabling developers to write portable code that can be compiled for both CUDA and HIP.
+
+- ``__HIP_DEVICE_COMPILE__`` : Defined exclusively during HIP device compilation, this macro allows for conditional compilation of device-specific code. It provides a mechanism to segregate device and host code, ensuring that each can be optimized for their respective execution environments.
+
 Function Pointers Support
 =========================