================ @@ -0,0 +1,316 @@ +=================== +HLSL Function Calls +=================== + +.. contents:: + :local: + +Introduction +============ + +This document describes the design and implementation of HLSL's function call +semantics in Clang. This includes details related to argument conversion and +parameter lifetimes. + +This document does not seek to serve as official documentation for HLSL's +call semantics, but does provide an overview to assist a reader. The +authoritative documentation for HLSL's language semantics is the `draft language +specification <https://microsoft.github.io/hlsl-specs/specs/hlsl.pdf>`_. + +Argument Semantics +================== + +In HLSL, all function arguments are passed by value in and out of functions. +HLSL has 3 keywords which denote the parameter semantics (``in``, ``out`` and +``inout``). In a function declaration a parameter may be annotated any of the +following ways: + +#. <no parameter annotation> - denotes input +#. ``in`` - denotes input +#. ``out`` - denotes output +#. ``in out`` - denotes input and output +#. ``out in`` - denotes input and output +#. ``inout`` - denotes input and output + +Parameters that are exclusively input behave like C/C++ parameters that are +passed by value. + +For parameters that are output (or input and output), a temporary value is +created in the caller. The temporary value is then passed by-address. For +output-only parameters, the temporary is uninitialized when passed (it is +undefined behavior to not explicitly initialize an ``out`` parameter inside a +function). For input and output parameters, the temporary is initialized from ---------------- tex3d wrote:
> (it is undefined behavior to not explicitly initialize an ``out`` parameter > inside a function) Perhaps it's better to say that an out parameter has an undefined value if not initialized inside the function, rather than this being considered undefined **_behavior_**? https://github.com/llvm/llvm-project/pull/75397 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
