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https://issues.apache.org/jira/browse/IMPALA-12390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17765781#comment-17765781
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ASF subversion and git services commented on IMPALA-12390:
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Commit f563cce6b8eed4519772af06d89edc6e374839d3 in impala's branch
refs/heads/branch-4.3.0 from Joe McDonnell
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=f563cce6b ]
IMPALA-12390 (part 1): Enable some clang-tidy performance related checks
This enables several Clang Tidy performance checks and fixes
the flagged code locations. The specific checks enabled are:
1. performance-faster-string-find
"warning: 'find' called with a string literal consisting of a
single character; consider using the more effective overload
accepting a character"
Fix: Use char literals rather than string literals
2. performance-for-range-copy
"warning: loop variable is copied but only used as const reference;
consider making it a const reference"
Fix: Use const & for some locations of auto
3. performance-implicit-cast-in-loop
"warning: the type of the loop variable '$VAR' is different from
the one returned by the iterator and generates an implicit cast;
you can either change the type to the correct one ('$TYPE' but
'const auto&' is always an option) or remove the reference to make
it explicit that you are creating a new value"
Fix: Use the right type or const auto&
4. performance-inefficient-vector-operation
"warning: 'push_back' is called inside a loop; consider pre-allocating
the vector capacity before the loop"
Fix: Call reserve() on the vector before the loop
5. performance-type-promotion-in-math-fn - not encountered in our code
This disables a few performance checks temporarily to keep the
change a reasonable size.
Testing:
- Ran bin/run_clang_tidy.sh with the new checks
- Ran GVO
Change-Id: I3d5dfe04ffb4ec6f156e268c31a356651410ce91
Reviewed-on: http://gerrit.cloudera.org:8080/20387
Tested-by: Impala Public Jenkins <[email protected]>
Reviewed-by: Michael Smith <[email protected]>
> Enable performance related clang-tidy checks
> --------------------------------------------
>
> Key: IMPALA-12390
> URL: https://issues.apache.org/jira/browse/IMPALA-12390
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Affects Versions: Impala 4.3.0
> Reporter: Joe McDonnell
> Assignee: Joe McDonnell
> Priority: Major
> Fix For: Impala 4.3.0
>
>
> clang-tidy has several performance-related checks that seem like they would
> be useful to enforce. Here are some examples:
> {noformat}
> /home/joemcdonnell/upstream/Impala/be/src/runtime/types.h:313:25: warning:
> loop variable is copied but only used as const reference; consider making it
> a const reference [performance-for-range-copy]
> for (ColumnType child_type : col_type.children) {
> ~~~~~~~~~~ ^
> const &
> /home/joemcdonnell/upstream/Impala/be/src/catalog/catalog-util.cc:168:34:
> warning: 'find' called with a string literal consisting of a single
> character; consider using the more effective overload accepting a character
> [performance-faster-string-find]
> int pos = object_name.find(".");
> ^~~~
> '.'
> /home/joemcdonnell/upstream/Impala/be/src/util/decimal-util.h:55:53: warning:
> the parameter 'b' is copied for each invocation but only used as a const
> reference; consider making it a const reference
> [performance-unnecessary-value-param]
> static int256_t SafeMultiply(int256_t a, int256_t b, bool may_overflow) {
> ~~~~~~~~ ^
> const &
> /home/joemcdonnell/upstream/Impala/be/src/codegen/llvm-codegen.cc:847:5:
> warning: 'push_back' is called inside a loop; consider pre-allocating the
> vector capacity before the loop [performance-inefficient-vector-operation]
> arguments.push_back(args_[i].type);
> ^{noformat}
> In all, they seem to flag things that developers wouldn't ordinarily notice,
> and it doesn't seem to have too many false positives. We should look into
> enabling these.
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