[PATCH] Expand macros in OpenMP pragmas.

[Richard Smith]

On Mon, Jun 15, 2015 at 9:30 AM, Samuel Antao <sfantao at us.ibm.com> wrote:

> Hi ABataev, hfinkel, rsmith,
>
> According to the OpenMP spec, all the preprocessor macros should be
> expanded in OpenMP pragmas. This patch adds support for that.
>

We already have support for that :) I assume you mean this patch adds
support for that *to -E*.


> http://reviews.llvm.org/D10446
>
> Files:
>   lib/Frontend/PrintPreprocessedOutput.cpp
>   test/OpenMP/preprocessor.c
>
> Index: lib/Frontend/PrintPreprocessedOutput.cpp
> ===================================================================
> --- lib/Frontend/PrintPreprocessedOutput.cpp
> +++ lib/Frontend/PrintPreprocessedOutput.cpp
> @@ -588,6 +588,37 @@
>      Callbacks->setEmittedDirectiveOnThisLine();
>    }
>  };
> +struct OMPPragmaHandler : public PragmaHandler {
> +  const char *Prefix;
> +  PrintPPOutputPPCallbacks *Callbacks;
> +
> +  OMPPragmaHandler(const char *prefix, PrintPPOutputPPCallbacks
> *callbacks)
> +      : Prefix(prefix), Callbacks(callbacks) {}
> +  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
> +                    Token &PragmaTok) override {
> +
> +    // The tokens after pragma omp need to be expanded.
> +    //
> +    //  OpenMP [2.1, Directive format]
> +    //  Preprocessing tokens following the #pragma omp are subject to
> macro
> +    //  replacement.
> +
> +    // Figure out what line we went to and insert the appropriate number
> of
> +    // newline characters.
> +    Callbacks->startNewLineIfNeeded();
> +    Callbacks->MoveToLine(PragmaTok.getLocation());
> +    Callbacks->OS.write(Prefix, strlen(Prefix));
> +    // Read and print all of the pragma tokens.
> +    while (PragmaTok.isNot(tok::eod)) {
> +      if (PragmaTok.hasLeadingSpace())
> +        Callbacks->OS << ' ';
>

Since you're doing macro expansion here, there are other ways in which you
can need a leading space before a token; you should also insert a space if
Callbacks->AvoidConcat says you need one (this is a pre-existing bug in the
UnknownPragmaHandler).

+      std::string TokSpell = PP.getSpelling(PragmaTok);
> +      Callbacks->OS.write(&TokSpell[0], TokSpell.size());
> +      PP.Lex(PragmaTok);
> +    }
> +    Callbacks->setEmittedDirectiveOnThisLine();
> +  }
> +};
>  } // end anonymous namespace
>
>
> @@ -722,6 +753,7 @@
>    PP.AddPragmaHandler("GCC", new UnknownPragmaHandler("#pragma
> GCC",Callbacks));
>    PP.AddPragmaHandler("clang",
>                        new UnknownPragmaHandler("#pragma clang",
> Callbacks));
> +  PP.AddPragmaHandler("omp", new OMPPragmaHandler("#pragma omp",
> Callbacks));
>

Instead of adding a new kind of PragmaHandler here, let's generalize the
existing infrastructure: please add a bool flag to UnknownPragmaHandler
that says whether to expand macros, set it to 'true' for omp and to
getLangOpts().MicrosoftExt for the other cases. (Using MicrosoftExt here
isn't right, but it matches our current behavior and we can correct it in a
later change.)


>    PP.addPPCallbacks(std::unique_ptr<PPCallbacks>(Callbacks));
>
> Index: test/OpenMP/preprocessor.c
> ===================================================================
> --- /dev/null
> +++ test/OpenMP/preprocessor.c
> @@ -0,0 +1,30 @@
> +// RUN:   %clang -fopenmp -E -o - %s 2>&1 | FileCheck %s
>

This should be a %clang_cc1 test, and should go in test/Preprocessor.

+
> +// This is to make sure the pragma name is not expanded!
> +#define omp (0xDEADBEEF)
> +
> +#define N 2
> +#define M 1
> +
> +#define map_to_be_expanded(x) map(tofrom:x)
> +#define sched_to_be_expanded(x) schedule(x,N)
> +#define reda_to_be_expanded(x) reduction(+:x)
> +#define redb_to_be_expanded(x,op) reduction(op:x)
> +
> +void foo(int *a, int *b) {
> +  //CHECK: omp target map(a[0:2]) map(tofrom:b[0:2*1])
> +  #pragma omp target map(a[0:N]) map_to_be_expanded(b[0:2*M])
> +  {
> +    int reda;
> +    int redb;
> +    //CHECK: omp parallel for schedule(static,2) reduction(+:reda)
> reduction(*:redb)
> +    #pragma omp parallel for sched_to_be_expanded(static) \
> +        reda_to_be_expanded(reda) redb_to_be_expanded(redb,*)
> +    for (int i = 0; i < N; ++i) {
> +      reda += a[i];
> +      redb += b[i];
> +    }
> +    a[0] = reda;
> +    b[0] = redb;
> +  }
> +}
>
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