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Re: [gcc] Enable DW_OP_VAL_EXPRESSION support in dwarf module

From: Jason Merrill <jason at redhat dot com>
To: Jiong Wang <jiong dot wang at foss dot arm dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
Cc: Jakub Jelinek <jakub at redhat dot com>
Date: Mon, 31 Oct 2016 15:50:38 -0400
Subject: Re: [gcc] Enable DW_OP_VAL_EXPRESSION support in dwarf module
Authentication-results: sourceware.org; auth=none
References: <3849486f-84ee-31ad-e01c-93dcdb8ca1fa@foss.arm.com>

On 10/21/2016 04:30 AM, Jiong Wang wrote:

All DW_OP_* of the expression are grouped together inside the PARALLEL,
and those operations which don't have RTL mapping are wrapped by
UNSPEC.  The parsing algorithm is simply something like:

  foreach elem inside PARALLEL
    if (UNSPEC)
      {
        dw_op_code = INTVAL (XVECEXP (elem, 0, 0));
        oprnd1 = INTVAL (XVECEXP (elem, 0, 1));
        oprnd2 = INTVAL (XVECEXP (elem, 0, 2));
      }
    else
      call standard RTL parser.

Any comments on the approach?

If you're going to use UNSPEC, why not put the DWARF operator in thesecond operand?


Jason

References:
- [gcc] Enable DW_OP_VAL_EXPRESSION support in dwarf module
  - From: Jiong Wang

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