class MemorySSAWalker

Declaration

class MemorySSAWalker { /* full declaration omitted */ };

Description

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.

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:995

Member Variables

protected llvm::MemorySSA* MSSA

Method Overview

Methods

MemorySSAWalker(llvm::MemorySSA*)

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:997

Parameters

llvm::MemorySSA* 

llvm::MemoryAccess* getClobberingMemoryAccess(
    const llvm::Instruction* I)

Description

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.

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:1024

Parameters

const llvm::Instruction* I

virtual llvm::MemoryAccess*
getClobberingMemoryAccess(llvm::MemoryAccess*)

Description

Does the same thing as getClobberingMemoryAccess(const Instruction *I), but takes a MemoryAccess instead of an Instruction.

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:1032

Parameters

llvm::MemoryAccess* 

virtual llvm::MemoryAccess*
getClobberingMemoryAccess(
    llvm::MemoryAccess*,
    const llvm::MemoryLocation&)

Description

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.

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:1045

Parameters

llvm::MemoryAccess*
const llvm::MemoryLocation& 

virtual void invalidateInfo(llvm::MemoryAccess*)

Description

Given a memory access, invalidate anything this walker knows about that access. This API is used by walkers that store information to perform basic cache invalidation. This will be called by MemorySSA at appropriate times for the walker it uses or returns.

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:1053

Parameters

llvm::MemoryAccess* 

virtual ~MemorySSAWalker()

Declared at: llvm/include/llvm/Analysis/MemorySSA.h:998