The LLVM Lexicon

Table Of Contents

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- A -
ADCE
- B -
BURS
- C -
CSE
- D -
DAG	Derived Pointer	DSA	DSE
- F -
FCA
- G -
GC
- I -
IPA	IPO	ISel
- L -
LCSSA	LICM	Load-VN	LTO
- M -
MC
- O -
Object Pointer
- P -
PRE
- R -
RAUW	Reassociation	Root	RPO
- S -
Safe Point	SCC	SCCP	SDISel	SRoA	Stack Map

Definitions

- -

- A -

ADCE: Aggressive Dead Code Elimination

- -

- B -

BURS: Bottom Up Rewriting System—A method of instruction selection for - code generation. An example is the BURG tool.

- -

- C -

CSE: Common Subexpression Elimination. An optimization that removes common - subexpression compuation. For example (a+b)*(a+b) has two - subexpressions that are the same: (a+b). This optimization would - perform the addition only once and then perform the multiply (but only if - it's compulationally correct/safe). -

- -

- D -

DAG: Directed Acyclic Graph
Derived Pointer: A pointer to the interior of an object, such that a garbage collector - is unable to use the pointer for reachability analysis. While a derived - pointer is live, the corresponding object pointer must be kept in a root, - otherwise the collector might free the referenced object. With copying - collectors, derived pointers pose an additional hazard that they may be - invalidated at any safe point. This term is used in - opposition to object pointer.
DSA: Data Structure Analysis
DSE: Dead Store Elimination

- -

- G -

GC: Garbage Collection. The practice of using reachability analysis instead - of explicit memory management to reclaim unused memory.

- -

- H -

Heap: In garbage collection, the region of memory which is managed using - reachability analysis.

- -

- I -

IPA: Inter-Procedural Analysis. Refers to any variety of code analysis that - occurs between procedures, functions or compilation units (modules).
IPO: Inter-Procedural Optimization. Refers to any variety of code - optimization that occurs between procedures, functions or compilation units - (modules).
ISel: Instruction Selection.

- -

- L -

LCSSA: Loop-Closed Static Single Assignment Form
LICM: Loop Invariant Code Motion
Load-VN: Load Value Numbering
LTO: Link-Time Optimization

- -

- O -

Object Pointer: A pointer to an object such that the garbage collector is able to trace - references contained within the object. This term is used in opposition to - derived pointer.

- - -

- P -

PRE: Partial Redundancy Elimination

- - -

- R -

RAUW: An abbreviation for Replace - All Uses With. The functions User::replaceUsesOfWith(), - Value::replaceAllUsesWith(), and Constant::replaceUsesOfWithOnConstant() - implement the replacement of one Value with another by iterating over its - def/use chain and fixing up all of the pointers to point to the new value. - See also def/use chains. -
Reassociation: Rearranging - associative expressions to promote better redundancy elimination and other - optimization. For example, changing (A+B-A) into (B+A-A), permitting it to - be optimized into (B+0) then (B).
Root: In garbage collection, a - pointer variable lying outside of the heap from which - the collector begins its reachability analysis. In the context of code - generation, "root" almost always refers to a "stack root" -- a local or - temporary variable within an executing function.
RPO: Reverse postorder

- - -

- S -

Safe Point: In garbage collection, it is necessary to identify stack - roots so that reachability analysis may proceed. It may be infeasible to - provide this information for every instruction, so instead the information - may is calculated only at designated safe points. With a copying collector, - derived pointers must not be retained across - safe points and object pointers must be - reloaded from stack roots.
SDISel: Selection DAG Instruction Selection.
SCC: Strongly Connected Component
SCCP: Sparse Conditional Constant Propagation
SRoA: Scalar Replacement of Aggregates
SSA: Static Single Assignment
Stack Map: In garbage collection, metadata emitted by the code generator which - identifies roots within the stack frame of an executing - function.

- -

`_ tool. + +C +- + +**CSE** + Common Subexpression Elimination. An optimization that removes common + subexpression compuation. For example ``(a+b)*(a+b)`` has two subexpressions + that are the same: ``(a+b)``. This optimization would perform the addition + only once and then perform the multiply (but only if it's compulationally + correct/safe). + +D +- + +**DAG** + Directed Acyclic Graph + +.. _derived pointer: +.. _derived pointers: + +**Derived Pointer** + A pointer to the interior of an object, such that a garbage collector is + unable to use the pointer for reachability analysis. While a derived pointer + is live, the corresponding object pointer must be kept in a root, otherwise + the collector might free the referenced object. With copying collectors, + derived pointers pose an additional hazard that they may be invalidated at + any `safe point`_. This term is used in opposition to `object pointer`_. + +**DSA** + Data Structure Analysis + +**DSE** + Dead Store Elimination + +F +- + +**FCA** + First Class Aggregate + +G +- + +**GC** + Garbage Collection. The practice of using reachability analysis instead of + explicit memory management to reclaim unused memory. + +H +- + +.. _heap: + +**Heap** + In garbage collection, the region of memory which is managed using + reachability analysis. + +I +- + +**IPA** + Inter-Procedural Analysis. Refers to any variety of code analysis that + occurs between procedures, functions or compilation units (modules). + +**IPO** + Inter-Procedural Optimization. Refers to any variety of code optimization + that occurs between procedures, functions or compilation units (modules). + +**ISel** + Instruction Selection + +L +- + +**LCSSA** + Loop-Closed Static Single Assignment Form + +**LICM** + Loop Invariant Code Motion + +**Load-VN** + Load Value Numbering + +**LTO** + Link-Time Optimization + +M +- + +**MC** + Machine Code + +O +- +.. _object pointer: +.. _object pointers: + +**Object Pointer** + A pointer to an object such that the garbage collector is able to trace + references contained within the object. This term is used in opposition to + `derived pointer`_. + +P +- + +**PRE** + Partial Redundancy Elimination + +R +- + +**RAUW** + + Replace All Uses With. The functions ``User::replaceUsesOfWith()``, + ``Value::replaceAllUsesWith()``, and + ``Constant::replaceUsesOfWithOnConstant()`` implement the replacement of one + Value with another by iterating over its def/use chain and fixing up all of + the pointers to point to the new value. See + also `def/use chains `_. + +**Reassociation** + Rearranging associative expressions to promote better redundancy elimination + and other optimization. For example, changing ``(A+B-A)`` into ``(B+A-A)``, + permitting it to be optimized into ``(B+0)`` then ``(B)``. + +.. _roots: +.. _stack roots: + +**Root** + In garbage collection, a pointer variable lying outside of the `heap`_ from + which the collector begins its reachability analysis. In the context of code + generation, "root" almost always refers to a "stack root" --- a local or + temporary variable within an executing function. + +**RPO** + Reverse postorder + +S +- + +.. _safe point: + +**Safe Point** + In garbage collection, it is necessary to identify `stack roots`_ so that + reachability analysis may proceed. It may be infeasible to provide this + information for every instruction, so instead the information may is + calculated only at designated safe points. With a copying collector, + `derived pointers`_ must not be retained across safe points and `object + pointers`_ must be reloaded from stack roots. + +**SDISel** + Selection DAG Instruction Selection. + +**SCC** + Strongly Connected Component + +**SCCP** + Sparse Conditional Constant Propagation + +**SRoA** + Scalar Replacement of Aggregates + +**SSA** + Static Single Assignment + +**Stack Map** + In garbage collection, metadata emitted by the code generator which + identifies `roots`_ within the stack frame of an executing function. diff --git a/docs/userguides.rst b/docs/userguides.rst index 3e8fb4cb85..0d1f3fb46a 100644 --- a/docs/userguides.rst +++ b/docs/userguides.rst @@ -8,6 +8,7 @@ User Guides CommandGuide/index FAQ + Lexicon * `The LLVM Getting Started Guide `_ @@ -69,7 +70,7 @@ User Guides Advice on packaging LLVM into a distribution. -* `The LLVM Lexicon `_ +* :ref:`lexicon` Definition of acronyms, terms and concepts used in LLVM. -- cgit v1.2.3