[PATCH] D138531: [PATCH] [NVPTX] Backend support for variadic functions

[Pavel Kopyl via Phabricator via llvm-commits]

pavelkopyl created this revision.
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This patch adds lowering for function calls with variadic number of arguments
as well as enables support for the following instructions/intrinsics:

- va_arg
- va_start
- va_end
- va_copy

Note that this patch doesn't intent to include clang's support for
variadic functions for CUDA.

According to the docs:

  PTX version 6.0 supports passing unsized array parameter to a function which
  can be used to implement variadic functions. [0]



  The last parameter in the parameter list may be a .param array of type .b8 with
  no size specified. It is used to pass an arbitrary number of parameters to
  the function packed into a single array object.
  
  When calling a function with such an unsized last argument, the last argument
  may be omitted from the call instruction if no parameter is passed through it.
  Accesses to this array parameter must be within the bounds of the array.
  The result of an access is undefined if no array was passed, or if the access
  was outside the bounds of the actual array being passed. [1]

Note that aggregates passed by value as variadic arguments are not currently
supported.

-

[0] https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#variadic-functions
[1] https://docs.nvidia.com/cuda/parallel-thread-execution/index.html#kernel-and-function-directives-func


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D138531

Files:
  llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
  llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
  llvm/lib/Target/NVPTX/NVPTXISelLowering.h
  llvm/lib/Target/NVPTX/NVPTXInstrInfo.td
  llvm/test/CodeGen/NVPTX/symbol-naming.ll
  llvm/test/CodeGen/NVPTX/vaargs.ll
  llvm/test/DebugInfo/NVPTX/dbg-value-const-byref.ll

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