[llvm] r237487 - MC: Change MCAssembler::Symbols to a vector

[David Blaikie]

On Fri, May 15, 2015 at 3:56 PM, Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:

> Author: dexonsmith
> Date: Fri May 15 17:56:01 2015
> New Revision: 237487
>
> URL: http://llvm.org/viewvc/llvm-project?rev=237487&view=rev
> Log:
> MC: Change MCAssembler::Symbols to a vector
>
> Instead of an intrusive double-linked linked list, use a
> `std::vector<>`.


Yay for fewer intrusive things! \o/


> This saves a pointer per symbol and simplifies
> `MCSymbolData`.  Otherwise, no functionality change here.
>
> While I measured a memory drop from around 1047MB to 1040MB (0.6%) --
> and this is a decent cleanup in its own right -- it's primarily a
> preparation patch for merging `MCSymbol` and `MCSymbolData`.  I'll post
> an updated patch for that to the list in a moment.
>
> (I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
> see r236629 for details.)
>
> Modified:
>     llvm/trunk/include/llvm/MC/MCAssembler.h
>
> Modified: llvm/trunk/include/llvm/MC/MCAssembler.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAssembler.h?rev=237487&r1=237486&r2=237487&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/MC/MCAssembler.h (original)
> +++ llvm/trunk/include/llvm/MC/MCAssembler.h Fri May 15 17:56:01 2015
> @@ -17,6 +17,7 @@
>  #include "llvm/ADT/SmallString.h"
>  #include "llvm/ADT/ilist.h"
>  #include "llvm/ADT/ilist_node.h"
> +#include "llvm/ADT/iterator.h"
>  #include "llvm/MC/MCDirectives.h"
>  #include "llvm/MC/MCFixup.h"
>  #include "llvm/MC/MCInst.h"
> @@ -657,7 +658,7 @@ public:
>  };
>
>  // FIXME: Same concerns as with SectionData.
> -class MCSymbolData : public ilist_node<MCSymbolData> {
> +class MCSymbolData {
>    const MCSymbol *Symbol;
>
>    /// Fragment - The fragment this symbol's value is relative to, if any.
> Also
> @@ -798,13 +799,14 @@ class MCAssembler {
>
>  public:
>    typedef iplist<MCSectionData> SectionDataListType;
> -  typedef iplist<MCSymbolData> SymbolDataListType;
> +  typedef std::vector<std::unique_ptr<MCSymbolData>> SymbolDataListType;
>
>    typedef SectionDataListType::const_iterator const_iterator;
>    typedef SectionDataListType::iterator iterator;
>
> -  typedef SymbolDataListType::const_iterator const_symbol_iterator;
> -  typedef SymbolDataListType::iterator symbol_iterator;
> +  typedef pointee_iterator<SymbolDataListType::const_iterator>
> +  const_symbol_iterator;
> +  typedef pointee_iterator<SymbolDataListType::iterator> symbol_iterator;
>
>    typedef iterator_range<symbol_iterator> symbol_range;
>    typedef iterator_range<const_symbol_iterator> const_symbol_range;
> @@ -846,7 +848,7 @@ private:
>
>    iplist<MCSectionData> Sections;
>
> -  iplist<MCSymbolData> Symbols;
> +  SymbolDataListType Symbols;
>
>    DenseSet<const MCSymbol *> LocalsUsedInReloc;
>
> @@ -1181,8 +1183,8 @@ public:
>      if (Created)
>        *Created = !Entry;
>      if (!Entry) {
> -      Entry = new MCSymbolData(Symbol, nullptr, 0);
> -      Symbols.push_back(Entry);
> +      Symbols.emplace_back(new MCSymbolData(Symbol, nullptr, 0));
> +      Entry = Symbols.back().get();
>      }
>
>      return *Entry;
>
>
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