Loop cloning: generalize recognized loop iteration patterns

[BruceForstall]

Currently, loop cloning only recognizes simple "count up" loops, e.g.,

for (i = c; i < x; i++)

The condition can be < or <=. x can be constant or a loop-invariant variable. c must be non-negative.

Consider handling additional patterns, such as "count down" loops (e.g., for (i = a.Length - 1; i >=0; i--)), or "nuint" cases (e.g., for (nuint i = (nuint)(arrLen - 1); i != nuint.MaxValue; i--)), and more.

One place this was suggested: #60148 (comment)

category:cq
theme:loop-opt
skill-level:expert
cost:medium
impact:medium

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Currently, loop cloning only recognizes simple "count up" loops, e.g.,

for (i = c; i < x; i++)

The condition can be < or <=. x can be constant or a loop-invariant variable. c must be non-negative.

Consider handling additional patterns, such as "count down" loops (e.g., for (i = a.Length - 1; i >=0; i--)), or "nuint" cases (e.g., for (nuint i = (nuint)(arrLen - 1); i != nuint.MaxValue; i--)), and more.

One place this was suggested: #60148 (comment)

category:cq
theme:loop-opt
skill-level:expert
cost:medium

Author:	BruceForstall
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-