[PATCH] D20337: [MC] Support symbolic expressions in assembly directives

[Rafael Espíndola via llvm-commits]

I mean filetype=asm :-)
On May 18, 2016 1:15 PM, "Rafael Espíndola" <rafael.espindola at gmail.com>
wrote:

> What happens if you try to print the assembly back out? I.e., if you run
> llvm-mc with filetype=obj?
>
> Cheers,
> Rafael
> On May 17, 2016 5:48 PM, "Petr Hosek via llvm-commits" <
> llvm-commits at lists.llvm.org> wrote:
>
> phosek created this revision.
> phosek added a subscriber: llvm-commits.
> phosek set the repository for this revision to rL LLVM.
>
> This matches the behavior of GNU assembler which supports symbolic
> expressions in absolute expressions used in assembly directives.
>
> Repository:
>   rL LLVM
>
> http://reviews.llvm.org/D20337
>
> Files:
>   include/llvm/MC/MCObjectStreamer.h
>   include/llvm/MC/MCStreamer.h
>   lib/MC/MCParser/AsmParser.cpp
>   test/MC/AsmParser/symbolic-expression.s
>
> Index: test/MC/AsmParser/symbolic-expression.s
> ===================================================================
> --- /dev/null
> +++ test/MC/AsmParser/symbolic-expression.s
> @@ -0,0 +1,18 @@
> +# RUN: llvm-mc -filetype=obj -triple=i386-unknown-elf %s | llvm-objdump
> -t - | FileCheck %s
> +
> +# CHECK: 00000000         .text           00000000 TEST0
> +TEST0:
> +  .fill 0x10
> +# CHECK: 00000010         .text           00000000 TEST1
> +TEST1:
> +  .fill TEST1 - TEST0 + 0x5
> +# CHECK: 00000025         .text           00000000 TEST2
> +TEST2:
> +  .zero TEST2 - (TEST1 + 0x5)
> +# CHECK: 00000035         .text           00000000 TEST3
> +TEST3:
> +  .align (TEST1 - TEST0) * 8
> +# CHECK: 00000080         .text           00000000 TEST4
> +TEST4:
> +# CHECK: 00000015 g       *COM*           00000010 a
> +  .comm a, TEST2 - TEST1, TEST1 - TEST0
> Index: lib/MC/MCParser/AsmParser.cpp
> ===================================================================
> --- lib/MC/MCParser/AsmParser.cpp
> +++ lib/MC/MCParser/AsmParser.cpp
> @@ -1131,7 +1131,7 @@
>    if (parseExpression(Expr))
>      return true;
>
> -  if (!Expr->evaluateAsAbsolute(Res))
> +  if (!getStreamer().evaluateAsAbsolute(Expr, Res))
>      return Error(StartLoc, "expected absolute expression");
>
>    return false;
> Index: include/llvm/MC/MCStreamer.h
> ===================================================================
> --- include/llvm/MC/MCStreamer.h
> +++ include/llvm/MC/MCStreamer.h
> @@ -772,6 +772,11 @@
>    void Finish();
>
>    virtual bool mayHaveInstructions(MCSection &Sec) const { return true; }
> +
> +  /// \brief Try to evaluate the \p Value as an absolute value.
> +  virtual bool evaluateAsAbsolute(const MCExpr *Value, int64_t &Res) {
> +    return Value->evaluateAsAbsolute(Res);
> +  }
>  };
>
>  /// Create a dummy machine code streamer, which does nothing. This is
> useful for
> Index: include/llvm/MC/MCObjectStreamer.h
> ===================================================================
> --- include/llvm/MC/MCObjectStreamer.h
> +++ include/llvm/MC/MCObjectStreamer.h
> @@ -154,6 +154,12 @@
>                                unsigned Size) override;
>
>    bool mayHaveInstructions(MCSection &Sec) const override;
> +
> +  bool evaluateAsAbsolute(const MCExpr *Value, int64_t &Res) override {
> +    MCDataFragment *DF = getOrCreateDataFragment();
> +    flushPendingLabels(DF, DF->getContents().size());
> +    return Value->evaluateAsAbsolute(Res, getAssembler());
> +  }
>  };
>
>  } // end namespace llvm
>
>
>
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