https://github.com/llvm-beanz created https://github.com/llvm/llvm-project/pull/84081
This adds a brief blurb about hlsl.h in the HLSLSupport documentation where a high level view of the architecture is explained. >From 081d397961bd19d37d957d43c67f6a419c338629 Mon Sep 17 00:00:00 2001 From: Chris Bieneman <chris.biene...@me.com> Date: Tue, 5 Mar 2024 16:26:17 -0600 Subject: [PATCH] [HLSL][docs] Document hlsl.h in the HLSL docs This adds a brief blurb about hlsl.h in the HLSLSupport documentation where a high level view of the architecture is explained. --- clang/docs/HLSL/HLSLSupport.rst | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/clang/docs/HLSL/HLSLSupport.rst b/clang/docs/HLSL/HLSLSupport.rst index b091c17fd2a764..ca1f8faf757529 100644 --- a/clang/docs/HLSL/HLSLSupport.rst +++ b/clang/docs/HLSL/HLSLSupport.rst @@ -114,6 +114,39 @@ not re-targetable, we want to share the Clang CodeGen implementation for HLSL with other GPU graphics targets like SPIR-V and possibly other GPU and even CPU targets. +hlsl.h +------ + +HLSL has an extensive library of built in functionality. This is similar to +OpenCL and CUDA. The implementation approach for the HLSL library functionality +draws from patterns in use by OpenCL and other built-in headers. + +Similar to OpenCL, the HLSL library functionality is implicitly declared in +translation units without needing to include a header to provide declarations. +In Clang this is handled by making ``hlsl.h`` an implicitly included header. + +Similar to OpenCL, HLSL's implicit header will explicitly declare all overloads, +and each overload will map to a corresponding builtin that is used for code +generation. CUDA uses a similar pattern although many CUDA built-in functions +have full definitions in the included headers which in turn call builtins. By +not having bodies we avoid the need for the inliner to clean up and inline the +small library functions. + +HLSL's implicit headers also define some of HLSL's built-in typedefs. This is +consistent with how the AVX vector header is implemented. + +Concerns have been expressed that this approach may result in slower compile +times than the approach DXC uses where built-in functions are treated more like +Clang builtins. While this might be true we have no existing shaders where +parsing is a significant compile-time overhead. Further, by treating these +built-in functions as functions rather than builtins the language behaviors are +more consistent and aligned with user expectation because normal overload +resolution rules and implicit conversions apply as expected. + +It is a feature of this design that clangd-powered "go to declaration" for +library functions will jump to a valid header declaration and all overloads will +be user readable. + HLSL Language ============= _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
