llvm::def_chain_iterator

Walks the defining accesses of MemoryDefs. Stops after we hit something that has no defining use (e.g. a MemoryPhi or liveOnEntry). Note that, when comparing against a null def_chain_iterator, this will compare equal only after walking said Phi/liveOnEntry.

Synopsis

Declared in <llvm/Analysis/MemorySSA.h>

template<
    class T,
    bool UseOptimizedChain = false>
struct def_chain_iterator
    : iterator_facade_base<def_chain_iterator<T, UseOptimizedChain>, std::forward_iterator_tag, MemoryAccess*>

Description

The UseOptimizedChain flag specifies whether to walk the clobbering access chain, or all the accesses.

Normally, MemoryDef are all just def/use linked together, so a def_chain on a MemoryDef will walk all MemoryDefs above it in the program until it hits a phi node. The optimized chain walks the clobbering access of a store. So if you are just trying to find, given a store, what the next thing that would clobber the same memory is, you want the optimized chain.

Base Classes

Name

Description

iterator_facade_base<def_chain_iterator<T, UseOptimizedChain>, std::forward_iterator_tag, MemoryAccess*>

CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of the interface.

Type Aliases

Name

Description

difference_type

Signed type used to express the distance between iterators.

iterator_category

Iterator category tag for this facade.

Pointer type returned by the iterator.

Reference type returned by the iterator.

Value type produced by the iterator.

Enums

Name

Description

Capability flags for the iterator category.

Member Functions

Name

Description

def_chain_iterator [constructor]

Constructors

Advance the iterator by n and return the result.

Post‐increment the iterator and return the previous value.

Retreat the iterator by n and return the result.

operator‐‐

Decrement operators

Return a proxy pointer to the current element.

Return a proxy to the element at offset n.

Equality operator

Return true if this iterator is less than or equal to RHS.

Return true if this iterator is greater than RHS.

Return true if this iterator is greater than or equal to RHS.

Protected Types

Name

Description

Proxy that yields a pointer from a copied reference.

ReferenceProxy

Proxy that yields a reference from a copied iterator.

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