[Webkit-unassigned] [Bug 197398] New: [B3] Tails of size 1 can be safely duplicated regardless of their number of predecessors

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=197398

            Bug ID: 197398
           Summary: [B3] Tails of size 1 can be safely duplicated
                    regardless of their number of predecessors
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Trivial
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: rmorisset at apple.com

Replacing a jump (one instruction) by a branch/switch/return (whatever the jump points to, also one instruction) cannot increase the number of instructions, and can be helpful to to things like foldPathConstants that run just after duplicateTails.

In most cases we already do this, as the block will have few predecessors, but we should do it unconditionally.
The benefit is almost certainly negligible (a quick experiment shows we only neglect to do this optimization 23 times on all of JetStream2), but the change is microscopic too (literally just one line).

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