[gcc/devel/rust/master] Merge #992

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:865b6090a8f8981cdfc050ea2ee44abbe92de141

commit 865b6090a8f8981cdfc050ea2ee44abbe92de141
Merge: 366c53371ad 7820ff8b8b1
Author: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Date:   Mon Mar 7 12:17:40 2022 +0000

    Merge #992
    
    992: Cleanup bad unused code warnings r=philberty a=philberty
    
    This patchset contains 4 distinct fixes:
    
    When a constant is declared after where it is used the code-generation pass falls
    back to a query compilation of the HIR::Item this did not contain a check to verify
    if it was already compiled and results in duplicate CONST_DECLS being generated
    if query compilation was used.
    
    We were using a zero precision integer to contain unit-type expressions this results
    in VAR_DECLS being lost in the GENERIC graph which does not allow us to perform
    any static analysis upon the DECL. This changes the unit type to use an empty struct
    and for initialization of a VAR_DECL we can simply pass an empty constructor and let
    GCC optimize this code for us.
    
    Update our DEAD_CODE scan to take into account modules of items and also respect
    if structures are prefixed with an underscore we can ignore generating an unused warning.
    
    Remove our AST scan for unused code and reuse GCC TREE_USED to track wether
    VAR_DECL, PARM_DECL, CONST_DECL are actually used or not. We reuse the GCC
    walk_tree functions to have this as nice separate lint.
    
    Fixes #676
    
    Co-authored-by: Philip Herron <philip.herron@embecosm.com>

Diff:

 gcc/rust/Make-lang.in                              |  1 +
 gcc/rust/backend/rust-compile-context.h            |  5 ++
 gcc/rust/backend/rust-compile-expr.cc              |  9 ++
 gcc/rust/backend/rust-compile-item.cc              |  4 +
 gcc/rust/backend/rust-compile-resolve-path.cc      | 22 ++++-
 gcc/rust/backend/rust-compile-stmt.h               |  9 +-
 gcc/rust/backend/rust-compile-tyty.h               |  8 +-
 gcc/rust/lang.opt                                  | 12 +++
 gcc/rust/lint/rust-lint-marklive.h                 |  6 ++
 gcc/rust/lint/rust-lint-scan-deadcode.h            | 14 +++-
 gcc/rust/lint/rust-lint-unused-var.cc              | 98 ++++++++++++++++++++++
 gcc/rust/lint/rust-lint-unused-var.h               | 36 ++++++++
 gcc/rust/resolve/rust-ast-resolve-unused.h         | 61 --------------
 gcc/rust/rust-gcc.cc                               | 22 ++---
 gcc/rust/rust-session-manager.cc                   | 29 +++----
 gcc/testsuite/rust/compile/array3.rs               |  1 -
 .../compile/torture/all_doc_comment_line_blocks.rs | 70 ++++++++--------
 .../torture/all_doc_comment_line_blocks_crlf.rs    | 10 +--
 .../rust/compile/torture/associated_types1.rs      |  2 -
 gcc/testsuite/rust/compile/torture/cfg_attr.rs     |  1 -
 gcc/testsuite/rust/compile/torture/generics13.rs   |  3 +-
 gcc/testsuite/rust/compile/torture/generics14.rs   |  3 +-
 gcc/testsuite/rust/compile/torture/generics18.rs   |  1 -
 gcc/testsuite/rust/compile/torture/generics24.rs   |  1 -
 .../rust/compile/torture/impl_block_unused.rs      | 10 +--
 gcc/testsuite/rust/compile/torture/issue-808.rs    |  2 -
 .../rust/compile/torture/mod-nameresolve.rs        |  4 +-
 gcc/testsuite/rust/compile/torture/mod1.rs         |  1 -
 gcc/testsuite/rust/compile/torture/mod2.rs         | 10 +--
 gcc/testsuite/rust/compile/torture/must_use2.rs    |  1 -
 .../rust/compile/torture/struct_init_4.rs          |  5 +-
 gcc/testsuite/rust/compile/torture/traits1.rs      |  1 -
 gcc/testsuite/rust/compile/torture/traits10.rs     |  1 -
 gcc/testsuite/rust/compile/torture/traits18.rs     |  3 -
 gcc/testsuite/rust/compile/torture/traits2.rs      |  1 -
 gcc/testsuite/rust/compile/torture/traits3.rs      |  3 -
 gcc/testsuite/rust/compile/torture/traits4.rs      |  3 -
 gcc/testsuite/rust/compile/torture/traits5.rs      |  3 -
 gcc/testsuite/rust/compile/torture/traits6.rs      |  2 -
 gcc/testsuite/rust/compile/torture/traits7.rs      |  3 -
 gcc/testsuite/rust/compile/torture/traits8.rs      |  1 -
 gcc/testsuite/rust/compile/torture/traits9.rs      |  3 -
 .../rust/compile/torture/tuple_enum_variants.rs    |  9 +-
 .../rust/compile/torture/tuple_struct_unused.rs    |  4 +-
 gcc/testsuite/rust/compile/torture/unused1.rs      |  1 -
 .../rust/compile/torture/unused_struct.rs          |  1 -
 gcc/testsuite/rust/compile/traits8.rs              |  2 -
 gcc/testsuite/rust/execute/torture/coercion1.rs    |  2 -
 gcc/testsuite/rust/execute/torture/coercion2.rs    |  2 -
 gcc/testsuite/rust/execute/torture/match2.rs       |  1 -
 gcc/testsuite/rust/execute/torture/mod1.rs         | 16 ++--
 .../rust/execute/torture/operator_overload_1.rs    |  3 -
 .../rust/execute/torture/operator_overload_10.rs   |  4 -
 .../rust/execute/torture/operator_overload_2.rs    |  3 -
 .../rust/execute/torture/operator_overload_3.rs    |  3 -
 .../rust/execute/torture/operator_overload_4.rs    |  2 -
 .../rust/execute/torture/operator_overload_5.rs    |  2 -
 .../rust/execute/torture/operator_overload_6.rs    |  3 -
 .../rust/execute/torture/operator_overload_7.rs    |  2 -
 .../rust/execute/torture/operator_overload_8.rs    |  3 -
 .../rust/execute/torture/operator_overload_9.rs    |  3 -
 gcc/testsuite/rust/execute/torture/trait10.rs      |  2 -
 gcc/testsuite/rust/execute/torture/trait11.rs      |  3 -
 gcc/testsuite/rust/execute/torture/trait12.rs      |  3 -
 gcc/testsuite/rust/execute/torture/trait13.rs      |  2 -
 gcc/testsuite/rust/execute/torture/trait4.rs       |  2 -
 gcc/testsuite/rust/execute/torture/trait5.rs       |  2 -
 gcc/testsuite/rust/execute/torture/trait6.rs       |  2 -
 gcc/testsuite/rust/execute/torture/trait7.rs       |  2 -
 gcc/testsuite/rust/execute/torture/trait8.rs       |  2 -
 gcc/testsuite/rust/execute/torture/trait9.rs       |  3 -
 71 files changed, 298 insertions(+), 276 deletions(-)