r239605 - [clang-format] Reorder and pack ParenState members to minimize padding

[Benjamin Kramer]

On Mon, Jun 15, 2015 at 1:01 PM, Manuel Klimek <klimek at google.com> wrote:
> On Mon, Jun 15, 2015 at 12:56 PM Benjamin Kramer <benny.kra at gmail.com>
> wrote:
>>
>> On Mon, Jun 15, 2015 at 6:30 AM, Manuel Klimek <klimek at google.com> wrote:
>> > Would have been interesting in the description to mention why it
>> > matters. 10
>> > bytes don't sound like much :)
>>
>> We copy millions of ParenState objects around. On formatting
>> X86ISelLowering.cpp this change saves 25 MB of vector allocations,
>> which is about 7-8% of the total memory allocations performed by
>> clang-format on that file. Peak memory doesn't change significantly
>> though.
>
>
> Does it affect runtime?

Runtime difference was in the noise in the things I tested.

- Ben

>>
>> > On Fri, Jun 12, 2015, 4:47 PM Benjamin Kramer <benny.kra at gmail.com>
>> > wrote:
>> >>
>> >> On Fri, Jun 12, 2015 at 4:28 PM, Daniel Jasper <djasper at google.com>
>> >> wrote:
>> >> > Thanks.. I also think we should simply use in-class initializers here
>> >> > instead of the constructor initializers where we constantly have to
>> >> > fix
>> >> > the
>> >> > order.
>> >>
>> >> Did so in r239606 for the integer members. Bitfields don't support
>> >> in-class initializers in C++11 :(
>> >>
>> >> - Ben
>> >>
>> >> > On Fri, Jun 12, 2015 at 3:07 PM, Benjamin Kramer
>> >> > <benny.kra at googlemail.com>
>> >> > wrote:
>> >> >>
>> >> >> Author: d0k
>> >> >> Date: Fri Jun 12 08:07:03 2015
>> >> >> New Revision: 239605
>> >> >>
>> >> >> URL: http://llvm.org/viewvc/llvm-project?rev=239605&view=rev
>> >> >> Log:
>> >> >> [clang-format] Reorder and pack ParenState members to minimize
>> >> >> padding
>> >> >>
>> >> >> sizeof(ParenState) goes from 64 bytes to 52 bytes. NFC.
>> >> >>
>> >> >> Modified:
>> >> >>     cfe/trunk/lib/Format/ContinuationIndenter.h
>> >> >>
>> >> >> Modified: cfe/trunk/lib/Format/ContinuationIndenter.h
>> >> >> URL:
>> >> >>
>> >> >>
>> >> >> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Format/ContinuationIndenter.h?rev=239605&r1=239604&r2=239605&view=diff
>> >> >>
>> >> >>
>> >> >>
>> >> >> ==============================================================================
>> >> >> --- cfe/trunk/lib/Format/ContinuationIndenter.h (original)
>> >> >> +++ cfe/trunk/lib/Format/ContinuationIndenter.h Fri Jun 12 08:07:03
>> >> >> 2015
>> >> >> @@ -148,15 +148,15 @@ struct ParenState {
>> >> >>    ParenState(unsigned Indent, unsigned IndentLevel, unsigned
>> >> >> LastSpace,
>> >> >>               bool AvoidBinPacking, bool NoLineBreak)
>> >> >>        : Indent(Indent), IndentLevel(IndentLevel),
>> >> >> LastSpace(LastSpace),
>> >> >> -        NestedBlockIndent(Indent), FirstLessLess(0),
>> >> >> -        BreakBeforeClosingBrace(false), QuestionColumn(0),
>> >> >> -        AvoidBinPacking(AvoidBinPacking),
>> >> >> BreakBeforeParameter(false),
>> >> >> -        NoLineBreak(NoLineBreak), LastOperatorWrapped(true),
>> >> >> ColonPos(0),
>> >> >> -        StartOfFunctionCall(0), StartOfArraySubscripts(0),
>> >> >> +        NestedBlockIndent(Indent), FirstLessLess(0),
>> >> >> QuestionColumn(0),
>> >> >> +        ColonPos(0), StartOfFunctionCall(0),
>> >> >> StartOfArraySubscripts(0),
>> >> >>          NestedNameSpecifierContinuation(0), CallContinuation(0),
>> >> >> VariablePos(0),
>> >> >> -        ContainsLineBreak(false), ContainsUnwrappedBuilder(0),
>> >> >> -        AlignColons(true), ObjCSelectorNameFound(false),
>> >> >> -        HasMultipleNestedBlocks(false), NestedBlockInlined(false)
>> >> >> {}
>> >> >> +        BreakBeforeClosingBrace(false),
>> >> >> AvoidBinPacking(AvoidBinPacking),
>> >> >> +        BreakBeforeParameter(false), NoLineBreak(NoLineBreak),
>> >> >> +        LastOperatorWrapped(true), ContainsLineBreak(false),
>> >> >> +        ContainsUnwrappedBuilder(false), AlignColons(true),
>> >> >> +        ObjCSelectorNameFound(false),
>> >> >> HasMultipleNestedBlocks(false),
>> >> >> +        NestedBlockInlined(false) {}
>> >> >>
>> >> >>    /// \brief The position to which a specific parenthesis level
>> >> >> needs
>> >> >> to
>> >> >> be
>> >> >>    /// indented.
>> >> >> @@ -182,31 +182,9 @@ struct ParenState {
>> >> >>    /// on a level.
>> >> >>    unsigned FirstLessLess;
>> >> >>
>> >> >> -  /// \brief Whether a newline needs to be inserted before the
>> >> >> block's
>> >> >> closing
>> >> >> -  /// brace.
>> >> >> -  ///
>> >> >> -  /// We only want to insert a newline before the closing brace if
>> >> >> there
>> >> >> also
>> >> >> -  /// was a newline after the beginning left brace.
>> >> >> -  bool BreakBeforeClosingBrace;
>> >> >> -
>> >> >>    /// \brief The column of a \c ? in a conditional expression;
>> >> >>    unsigned QuestionColumn;
>> >> >>
>> >> >> -  /// \brief Avoid bin packing, i.e. multiple parameters/elements
>> >> >> on
>> >> >> multiple
>> >> >> -  /// lines, in this context.
>> >> >> -  bool AvoidBinPacking;
>> >> >> -
>> >> >> -  /// \brief Break after the next comma (or all the commas in this
>> >> >> context if
>> >> >> -  /// \c AvoidBinPacking is \c true).
>> >> >> -  bool BreakBeforeParameter;
>> >> >> -
>> >> >> -  /// \brief Line breaking in this context would break a formatting
>> >> >> rule.
>> >> >> -  bool NoLineBreak;
>> >> >> -
>> >> >> -  /// \brief True if the last binary operator on this level was
>> >> >> wrapped
>> >> >> to the
>> >> >> -  /// next line.
>> >> >> -  bool LastOperatorWrapped;
>> >> >> -
>> >> >>    /// \brief The position of the colon in an ObjC method
>> >> >> declaration/call.
>> >> >>    unsigned ColonPos;
>> >> >>
>> >> >> @@ -230,40 +208,62 @@ struct ParenState {
>> >> >>    /// Used to align further variables if necessary.
>> >> >>    unsigned VariablePos;
>> >> >>
>> >> >> +  /// \brief Whether a newline needs to be inserted before the
>> >> >> block's
>> >> >> closing
>> >> >> +  /// brace.
>> >> >> +  ///
>> >> >> +  /// We only want to insert a newline before the closing brace if
>> >> >> there
>> >> >> also
>> >> >> +  /// was a newline after the beginning left brace.
>> >> >> +  bool BreakBeforeClosingBrace : 1;
>> >> >> +
>> >> >> +  /// \brief Avoid bin packing, i.e. multiple parameters/elements
>> >> >> on
>> >> >> multiple
>> >> >> +  /// lines, in this context.
>> >> >> +  bool AvoidBinPacking : 1;
>> >> >> +
>> >> >> +  /// \brief Break after the next comma (or all the commas in this
>> >> >> context if
>> >> >> +  /// \c AvoidBinPacking is \c true).
>> >> >> +  bool BreakBeforeParameter : 1;
>> >> >> +
>> >> >> +  /// \brief Line breaking in this context would break a formatting
>> >> >> rule.
>> >> >> +  bool NoLineBreak : 1;
>> >> >> +
>> >> >> +  /// \brief True if the last binary operator on this level was
>> >> >> wrapped
>> >> >> to the
>> >> >> +  /// next line.
>> >> >> +  bool LastOperatorWrapped : 1;
>> >> >> +
>> >> >>    /// \brief \c true if this \c ParenState already contains a
>> >> >> line-break.
>> >> >>    ///
>> >> >>    /// The first line break in a certain \c ParenState causes extra
>> >> >> penalty so
>> >> >>    /// that clang-format prefers similar breaks, i.e. breaks in the
>> >> >> same
>> >> >>    /// parenthesis.
>> >> >> -  bool ContainsLineBreak;
>> >> >> +  bool ContainsLineBreak : 1;
>> >> >>
>> >> >>    /// \brief \c true if this \c ParenState contains multiple
>> >> >> segments
>> >> >> of
>> >> >> a
>> >> >>    /// builder-type call on one line.
>> >> >> -  bool ContainsUnwrappedBuilder;
>> >> >> +  bool ContainsUnwrappedBuilder : 1;
>> >> >>
>> >> >>    /// \brief \c true if the colons of the curren ObjC method
>> >> >> expression
>> >> >> should
>> >> >>    /// be aligned.
>> >> >>    ///
>> >> >>    /// Not considered for memoization as it will always have the
>> >> >> same
>> >> >> value at
>> >> >>    /// the same token.
>> >> >> -  bool AlignColons;
>> >> >> +  bool AlignColons : 1;
>> >> >>
>> >> >>    /// \brief \c true if at least one selector name was found in the
>> >> >> current
>> >> >>    /// ObjC method expression.
>> >> >>    ///
>> >> >>    /// Not considered for memoization as it will always have the
>> >> >> same
>> >> >> value at
>> >> >>    /// the same token.
>> >> >> -  bool ObjCSelectorNameFound;
>> >> >> +  bool ObjCSelectorNameFound : 1;
>> >> >>
>> >> >>    /// \brief \c true if there are multiple nested blocks inside
>> >> >> these
>> >> >> parens.
>> >> >>    ///
>> >> >>    /// Not considered for memoization as it will always have the
>> >> >> same
>> >> >> value at
>> >> >>    /// the same token.
>> >> >> -  bool HasMultipleNestedBlocks;
>> >> >> +  bool HasMultipleNestedBlocks : 1;
>> >> >>
>> >> >>    // \brief The start of a nested block (e.g. lambda introducer in
>> >> >> C++
>> >> >> or
>> >> >>    // "function" in JavaScript) is not wrapped to a new line.
>> >> >> -  bool NestedBlockInlined;
>> >> >> +  bool NestedBlockInlined : 1;
>> >> >>
>> >> >>    bool operator<(const ParenState &Other) const {
>> >> >>      if (Indent != Other.Indent)
>> >> >>
>> >> >>
>> >> >> _______________________________________________
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>> >> >> cfe-commits at cs.uiuc.edu
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>> >> >
>> >> >
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