As a follow-up to PR#165841, this change addresses `prof_md` metadata
loss in AtomicExpandPass when lowering `atomicrmw xchg` to a
Load-Linked/Store-Exclusive (LL/SC) loop.
This path is distinct from the LSE path addressed previously:
PR #165841 (and its tests) used `-mtriple=aarch64-linux-gnu`, which
targets a modern **ARMv8.1+** architecture. This architecture supports
**Large System Extensions (LSE)**, allowing `atomicrmw` to be lowered
directly to a more efficient hardware instruction.
This PR (and its tests) uses `-mtriple=aarch64--` or
`-mtriple=armv8-linux-gnueabihf`. This indicates an `ARMv8.0 or lower
architecture that does not support LSE`. On these targets, the pass must
fall back to synthesizing a manual LL/SC loop using the `ldaxr/stxr`
instruction pair.
Similar to previous issue, the new conditional branch was failin to
inherit the `prof_md` metadata. Theis PR correctly fix the branch
weights to the newly created branch within the LL/SC loop, ensuring
profile information is preserved.
Co-authored-by: Jin Huang <jingold@google.com>
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