[PATCH] [OPENMP] A helper for marking intstructions with llvm.mem.parallel_loop_access

[Tyler Nowicki]

Hi Alexander,

Looks like this implementation is an alternative to the patch I am proposing. I’m pretty sure I also saw something like this on the list before. There are a few things I am concerned about with this approach. I am new to clang development though so please let me know what I misunderstood anything.

1. The pragma is not part of the AST. This makes the pragmas hidden to any passes over the AST. That may cause problems for features like serialization/deserialization and ast-print. If the pragma is an AST node those are easily supported.

2. Templates. I know there is a lot of interest in allowing the loop vectorization pragmas to take non-type template parameters. It has been a much requested feature on my patch. One of the challenges I am finding is that the non-type template parameters should be resolved on template instantiation. This probably has to occur when AST nodes are visited during semantic analysis. A few people have commented that they don’t want it in CodeGen because that would mean the verification of the input values would occur in codegen as well (see link [1] below). I’m still trying to figure this one out. But I am wondering how would you do it?

2. Efficiency. It looks like you have to make an extra pass over every loop.cond and loop.body even if metadata was not attached to those loops? Or did I miss something?

As I said, I’m new to clang so if I misunderstood anything please let me know.

Tyler

[1] - http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20140505/104925.html

On May 7, 2014, at 6:13 AM, Alexander Musman <alexander.musman at gmail.com> wrote:

> Hi doug.gregor, rjmccall, rsmith, ABataev, hfinkel, gribozavr, cbergstrom, rengolin, TylerNowicki,
> 
> This patch adds a helper class (CGLoopInfo) for marking memory instructions with llvm.mem.parallel_loop_access metadata.
> It also adds a simple initial version of codegen for pragma omp simd (it will change in the future to support all the clauses).
> 
> http://reviews.llvm.org/D3644
> 
> Files:
>  lib/CodeGen/CGBuilder.h
>  lib/CodeGen/CGLoopInfo.cpp
>  lib/CodeGen/CGLoopInfo.h
>  lib/CodeGen/CGStmt.cpp
>  lib/CodeGen/CGStmtOpenMP.cpp
>  lib/CodeGen/CMakeLists.txt
>  lib/CodeGen/CodeGenFunction.cpp
>  lib/CodeGen/CodeGenFunction.h
>  test/OpenMP/simd_metadata.c
> <D3644.9161.patch>