[lld] [LLD][ELF] Fix SHF_MERGE misalignment when spilled (PR #119289)

[Fangrui Song via llvm-commits]

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@@ -253,8 +253,22 @@ void OutputSection::finalizeInputSections() {
     for (InputSection *s : isd->sections)
       commitSection(s);
   }
-  for (auto *ms : mergeSections)
+  for (auto *ms : mergeSections) {
+    // Merging may have increased the alignment of a spillable section. Update
+    // the alignment of potential spill sections and their containing output
+    // sections.
+    if (!script->potentialSpillLists.empty()) {
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MaskRay wrote:

The `empty()` test is redundant

https://github.com/llvm/llvm-project/pull/119289