Loop Management
A loop header (sometimes called the entry point of the loop) is a dominator that is the target of a loop-forming back edge. The loop header dominates all blocks in the loop body.
Suppose block M is a dominator with several incoming edges, some of them being back edges (so M is a loop header). It is advantageous to several optimization passes to break M up into two blocks Mpre and Mloop. The contents of M and back edges are moved to Mloop, the rest of the edges are moved to point into Mpre, and a new edge from Mpre to Mloop is inserted (so that Mpre is the immediate dominator of Mloop). In the beginning, Mpre would be empty, but passes like loop-invariant code motion could populate it. Mpre is called the loop pre-header, and Mloop would be the loop header.
Read more about this topic: Control Flow Graph
Famous quotes containing the word management:
“No officer should be required or permitted to take part in the management of political organizations, caucuses, conventions, or election campaigns. Their right to vote and to express their views on public questions, either orally or through the press, is not denied, provided it does not interfere with the discharge of their official duties. No assessment for political purposes on officers or subordinates should be allowed.”
—Rutherford Birchard Hayes (1822–1893)