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[AST] Pack the unsigned of PackExpansionType into Type 

The bit-fields of `Type` have enough space for
the `unsigned NumExpansions` of `PackExpansionType`

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D50711

llvm-svn: 339789
This commit is contained in:
Bruno Ricci 2018-08-15 16:28:58 +00:00
parent 88d267d094
commit 58e577cb25
1 changed files with 28 additions and 13 deletions
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41
clang/include/clang/AST/Type.h
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@ -1624,6 +1624,25 @@ protected:
unsigned NumArgs;
};
class PackExpansionTypeBitfields {
friend class PackExpansionType;
unsigned : NumTypeBits;
/// The number of expansions that this pack expansion will
/// generate when substituted (+1), which is expected to be able to
/// hold at least 1024 according to [implimits]. However, as this limit
/// is somewhat easy to hit with template metaprogramming we'd prefer to
/// keep it as large as possible. At the moment it has been left as a
/// non-bitfield since this type safely fits in 64 bits as an unsigned, so
/// there is no reason to introduce the performance impact of a bitfield.
///
/// This field will only have a non-zero value when some of the parameter
/// packs that occur within the pattern have been substituted but others
/// have not.
unsigned NumExpansions;
};
union {
TypeBitfields TypeBits;
ArrayTypeBitfields ArrayTypeBits;
@ -1636,6 +1655,7 @@ protected:
TypeWithKeywordBitfields TypeWithKeywordBits;
VectorTypeBitfields VectorTypeBits;
TemplateSpecializationTypeBitfields TemplateSpecializationTypeBits;
PackExpansionTypeBitfields PackExpansionTypeBits;
static_assert(sizeof(TypeBitfields) <= 8,
"TypeBitfields is larger than 8 bytes!");
@ -1660,6 +1680,8 @@ protected:
static_assert(sizeof(TemplateSpecializationTypeBitfields) <= 8,
"TemplateSpecializationTypeBitfields is larger"
" than 8 bytes!");
static_assert(sizeof(PackExpansionTypeBitfields) <= 8,
"PackExpansionTypeBitfields is larger than 8 bytes");
};
private:
@ -5189,22 +5211,16 @@ class PackExpansionType : public Type, public llvm::FoldingSetNode {
/// The pattern of the pack expansion.
QualType Pattern;
/// The number of expansions that this pack expansion will
/// generate when substituted (+1), or indicates that
///
/// This field will only have a non-zero value when some of the parameter
/// packs that occur within the pattern have been substituted but others have
/// not.
unsigned NumExpansions;
PackExpansionType(QualType Pattern, QualType Canon,
Optional<unsigned> NumExpansions)
: Type(PackExpansion, Canon, /*Dependent=*/Pattern->isDependentType(),
/*InstantiationDependent=*/true,
/*VariablyModified=*/Pattern->isVariablyModifiedType(),
/*ContainsUnexpandedParameterPack=*/false),
Pattern(Pattern),
NumExpansions(NumExpansions ? *NumExpansions + 1 : 0) {}
Pattern(Pattern) {
PackExpansionTypeBits.NumExpansions =
NumExpansions ? *NumExpansions + 1 : 0;
}
public:
/// Retrieve the pattern of this pack expansion, which is the
@ -5215,9 +5231,8 @@ public:
/// Retrieve the number of expansions that this pack expansion will
/// generate, if known.
Optional<unsigned> getNumExpansions() const {
if (NumExpansions)
return NumExpansions - 1;
if (PackExpansionTypeBits.NumExpansions)
return PackExpansionTypeBits.NumExpansions - 1;
return None;
}