LLVM: llvm::MemorySSAWalker Class Reference (original) (raw)

This is the generic walker interface for walkers of MemorySSA. More...

#include "[llvm/Analysis/MemorySSA.h](MemorySSA%5F8h%5Fsource.html)"

This is the generic walker interface for walkers of MemorySSA.

Walkers are used to be able to further disambiguate the def-use chains MemorySSA gives you, or otherwise produce better info than MemorySSA gives you. In particular, while the def-use chains provide basic information, and are guaranteed to give, for example, the nearest may-aliasing MemoryDef for a MemoryUse as AliasAnalysis considers it, a user mant want better or other information. In particular, they may want to use SCEV info to further disambiguate memory accesses, or they may want the nearest dominating may-aliasing MemoryDef for a call or a store. This API enables a standardized interface to getting and using that info.

Definition at line 1024 of file MemorySSA.h.

◆ MemoryAccessSet

◆ ~MemorySSAWalker()

◆ getClobberingMemoryAccess() [1/6]

◆ getClobberingMemoryAccess() [2/6]

Given a memory Mod/Ref/ModRef'ing instruction, calling this will give you the nearest dominating MemoryAccess that Mod's the location the instruction accesses (by skipping any def which AA can prove does not alias the location(s) accessed by the instruction given).

Note that this will return a single access, and it must dominate the Instruction, so if an operand of a MemoryPhi node Mod's the instruction, this will return the MemoryPhi, not the operand. This means that given: if (a) { 1 = MemoryDef(liveOnEntry) store a } else { 2 = MemoryDef(liveOnEntry) store b } 3 = MemoryPhi(2, 1) MemoryUse(3) load a

calling this API on load(a) will return the MemoryPhi, not the MemoryDef in the if (a) branch.

Definition at line 1053 of file MemorySSA.h.

References assert(), getClobberingMemoryAccess(), I, and MSSA.

Referenced by getClobberingMemoryAccess(), getClobberingMemoryAccess(), getClobberingMemoryAccess(), getClobberingMemoryAccess(), getClobberingMemoryAccess(), getMatchingValue(), llvm::AMDGPU::isClobberedInFunction(), overreadUndefContents(), writtenBetween(), llvm::MemorySSA::CachingWalker::~CachingWalker(), and llvm::MemorySSA::SkipSelfWalker::~SkipSelfWalker().

◆ getClobberingMemoryAccess() [3/6]

◆ getClobberingMemoryAccess() [4/6]

Given a potentially clobbering memory access and a new location, calling this will give you the nearest dominating clobbering MemoryAccess (by skipping non-aliasing def links).

This version of the function is mainly used to disambiguate phi translated pointers, where the value of a pointer may have changed from the initial memory access. Note that this expects to be handed either a MemoryUse, or an already potentially clobbering access. Unlike the above API, if given a MemoryDef that clobbers the pointer as the starting access, it will return that MemoryDef, whereas the above would return the clobber starting from the use side of the memory def.

Implemented in llvm::DoNothingMemorySSAWalker, llvm::MemorySSA::CachingWalker, and llvm::MemorySSA::SkipSelfWalker.

◆ getClobberingMemoryAccess() [5/6]

◆ getClobberingMemoryAccess() [6/6]

◆ invalidateInfo()

◆ MemorySSA

◆ MSSA

The documentation for this class was generated from the following files:

• include/llvm/Analysis/MemorySSA.h
• lib/Analysis/MemorySSA.cpp