Only inline bare GlobalRef statements on Julia 1.12+

[CarloLucibello]

Summary

The GlobalRef branch in IR(::CodeInfo, ...) (src/ir/wrap.jl) inlines bare GlobalRef statements into their use sites. It was added in #134 to undo Julia 1.12's lowering change, which hoists a call's callee into its own statement:

# Julia 1.12 lowers `a * b` to:
%1 = Main.:*
%2 = (%1)(_2, _3)
# IRTools folds it back to the pre-1.12 shape:
%2 = _2 * _3

The branch was unconditional, so it also ran on Julia 1.10/1.11. There, code_lowered never produces a bare GlobalRef statement — but downstream IR producers do. In particular Zygote's forward-mode dynamo emits bare GlobalRef statements, and folding those into their uses reshapes the IR enough that the dynamo's recursion stops terminating, blowing the stack with a StackOverflowError.

This surfaced as a CI failure in Zygote on Julia 1.10 after it bumped to IRTools 0.4.16 (FluxML/Zygote.jl#1638): nested forward-mode AD (pushforward of pushforward) recurses infinitely through literal_indexed_iterate.

Fix

Gate the branch behind VERSION >= v"1.12.0-DEV.173" — the same boundary already used for the 1.12 debug-info handling in this file — so pre-1.12 behaviour is exactly as it was before #134.

Validation

• Reproduced the Zygote StackOverflowError on Julia 1.10 with registered IRTools 0.4.16; confirmed it disappears with this change while unrelated Zygote code is untouched.
• IRTools test suite passes on Julia 1.10 and 1.12.
• Zygote forward-mode tests + full Zygote suite pass on Julia 1.10 and 1.12 against this branch.
• Verified empirically that Julia 1.12 hoists callees (so the branch is still needed there) and Julia 1.10 does not (so it must not fire).

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.09%. Comparing base (6675b01) to head (4b8c062).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #139   +/-   ##
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  Coverage   74.09%   74.09%           
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  Files          15       15           
  Lines        1521     1521           
=======================================
  Hits         1127     1127           
  Misses        394      394           

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