[proggeramlug]

Problem

After #13017, running scripts/gc_root_dominance_check.py on tssrc's fully optimized Project unit with zero budgets still reported 97 unrooted values and 0 stale ones. The findings are identical on main before and after #12999.

Cause

All 97 are strhandle loads from string-literal handle globals. Each handle global is defined constant and points at an executable string image, which the collector never moves or reclaims (string_pool/image.rs, runtime is_image_string). -Os hoists these loads above safepoints:

How the load ended up above the safepoint	Count
i64 hoisted out of a loop or region	62
double hoisted the same way	26
GVN partial-redundancy elimination (PRE)	5
Inlined callee	4

A register loaded from a constant global can't go stale relative to that global. If the object could move, the global itself would be stale. So these registers aren't heap-value sources. The standard pmdom corpora don't hit this because they run only always-inline, mem2reg, sccp and dce before RS4GC.

Change

The checker collects each module's constant global definitions and doesn't treat a load whose pointer operand is one of them as a heap-value source. This applies in both statepoint and stale-register modes. global handles (dylib, staticlib, Mach-O runtime-boxed images, TLS strings) keep the #7240 classification.

Verification

• --self-test passes. The new positive cases fail without the fix. The negative control, the same handle declared global, still reports 1 unrooted strhandle.
• Full Project unit: 97 → 0 unrooted, 0 stale, on both base and head.
• Standard native and dep corpora: 0/0, with 40/40 planted violations caught in each.

Not covered: on macOS the handles are mutable globals pointing to the same immovable images, so a fully optimized Mac IR check would still flag them. That needs a separate exemption grounded in the runtime's guarantee.

[coderabbitai]

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