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MC: Shave a pointer off of MCSymbol::Name

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Shave a pointer off of `MCSymbolName` by storing `StringMapEntry<bool>*`
instead of `StringRef`.  This brings `sizeof(MCSymbol)` down to 64 on
64-bit platforms, a nice round number.  My profile showed memory
dropping from 914 MB down to 908 MB, roughly 0.7%.  Other than memory
usage, no functionality change here.

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238005 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2015-05-22 06:04:42 +00:00
parent b7888bd5ea
commit f5e0674d06
2 changed files with 8 additions and 9 deletions
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10
include/llvm/MC/MCSymbol.h
View File

@ -15,7 +15,7 @@
#define LLVM_MC_MCSYMBOL_H
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/Support/Compiler.h"
@ -145,7 +145,7 @@ class MCSymbol {
/// Name - The name of the symbol. The referred-to string data is actually
/// held by the StringMap that lives in MCContext.
StringRef Name;
const StringMapEntry<bool> *Name;
/// The section the symbol is defined in. This is null for undefined symbols,
/// and the special AbsolutePseudoSection value for absolute symbols. If this
@ -176,8 +176,8 @@ class MCSymbol {
private: // MCContext creates and uniques these.
friend class MCExpr;
friend class MCContext;
MCSymbol(StringRef name, bool isTemporary)
: Name(name), Section(nullptr), Value(nullptr), IsTemporary(isTemporary),
MCSymbol(const StringMapEntry<bool> *Name, bool isTemporary)
: Name(Name), Section(nullptr), Value(nullptr), IsTemporary(isTemporary),
IsRedefinable(false), IsUsed(false), HasData(false), Index(0) {}
MCSymbol(const MCSymbol &) = delete;
@ -190,7 +190,7 @@ private: // MCContext creates and uniques these.
public:
/// getName - Get the symbol name.
StringRef getName() const { return Name; }
StringRef getName() const { return Name ? Name->first() : ""; }
bool hasData() const { return HasData; }

7
lib/MC/MCContext.cpp
View File

@ -125,7 +125,7 @@ MCSymbol *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
}
auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
Sym = new (*this) MCSymbol(NameIter->getKey(), /*isTemporary*/ false);
Sym = new (*this) MCSymbol(&*NameIter, /*isTemporary*/ false);
if (!OldSym)
OldSym = Sym;
@ -156,7 +156,7 @@ MCSymbol *MCContext::CreateSymbol(StringRef Name, bool AlwaysAddSuffix) {
IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
if (IsTemporary && AlwaysAddSuffix && !UseNamesOnTempLabels)
return new (*this) MCSymbol("", true);
return new (*this) MCSymbol(nullptr, true);
SmallString<128> NewName = Name;
bool AddSuffix = AlwaysAddSuffix;
@ -170,8 +170,7 @@ MCSymbol *MCContext::CreateSymbol(StringRef Name, bool AlwaysAddSuffix) {
if (NameEntry.second) {
// Ok, we found a name. Have the MCSymbol object itself refer to the copy
// of the string that is embedded in the UsedNames entry.
MCSymbol *Result =
new (*this) MCSymbol(NameEntry.first->getKey(), IsTemporary);
MCSymbol *Result = new (*this) MCSymbol(&*NameEntry.first, IsTemporary);
return Result;
}
assert(IsTemporary && "Cannot rename non-temporary symbols");