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

Manuel Klimek klimek at google.com
Mon Jun 15 04:01:49 PDT 2015 

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?


>
> - 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)
> >> >>
> >> >>
> >> >> _______________________________________________
> >> >> cfe-commits mailing list
> >> >> cfe-commits at cs.uiuc.edu
> >> >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> >> >
> >> >
> >> _______________________________________________
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