mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-12-02 08:26:29 +00:00
195 lines
4.3 KiB
ReStructuredText
195 lines
4.3 KiB
ReStructuredText
.. _lexicon:
|
|
|
|
================
|
|
The LLVM Lexicon
|
|
================
|
|
|
|
.. note::
|
|
|
|
This document is a work in progress!
|
|
|
|
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
|
|
<http://www.program-transformation.org/Transform/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:
|
|
.. _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 <ProgrammersManual.html#iterate_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.</dd>
|
|
|
|
**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.
|