[all-commits] [llvm/llvm-project] b3b411: [demangler] Add operator precedence

[Nathan Sidwell via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: b3b4113a23756eb5f519ff473295483874d8e164
      https://github.com/llvm/llvm-project/commit/b3b4113a23756eb5f519ff473295483874d8e164
  Author: Nathan Sidwell <nathan at acm.org>
  Date:   2022-03-28 (Mon, 28 Mar 2022)

  Changed paths:
    M libcxxabi/src/demangle/ItaniumDemangle.h
    M libcxxabi/src/demangle/Utility.h
    M libcxxabi/test/test_demangle.pass.cpp
    M llvm/include/llvm/Demangle/ItaniumDemangle.h
    M llvm/include/llvm/Demangle/Utility.h

  Log Message:
  -----------
  [demangler] Add operator precedence

The demangler had no concept of operator precendence, and would
parenthesize many more subexpressions than necessary.  In particular
it would parenthesize primary-expressions, such as '4', which just
looks strange.  It would also parenthesize '>' expressions, just in
case they were inside a template parameter list.

This patch fixes both issues.

* Add operator precedence to the OpInfo structure, and add a
  subexpression helper that will parenthesize a lower precedence
  subexpression.

* Add a 'greater-than is greater-than' indicator to the output buffer,
  so the expression printer knows whether it is immediately inside a
  template parameter list (and must therefore parenthesize 'expr >
  expr').  This is a counter, so that ...

* Add open and close printers to the output buffer, that increment and
  decrement the gt-is-gt indicator.

* Parenthesize comma operators inside comma-separated lists. (probably
  a rare case, but still).

This dramatically reduces the extraneous parentheses being printed.

Reviewed By: dblaikie, bruno

Differential Revision: https://reviews.llvm.org/D120905