[llvm] AsmPrinter: Remove ELF's special lowerRelativeReference for unnamed_addr function; use lowerDSOLocalEquivalent in more cases (PR #134781)

[YongKang Zhu via llvm-commits]

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@@ -3496,10 +3496,12 @@ const MCExpr *AsmPrinter::lowerConstant(const Constant *CV,
           LHSGV, RHSGV, Addend, PCRelativeOffset, TM);
 
       // (ELF-specific) If the generic symbol difference does not apply, and
-      // LHS is a dso_local_equivalent of a dso_preemptable function,
-      // reference the PLT entry instead.
-      if (DSOEquiv && TM.getTargetTriple().isOSBinFormatELF() &&
-          !(LHSGV->isDSOLocal() || LHSGV->isImplicitDSOLocal()))
+      // LHS is a dso_local_equivalent of a function, reference the PLT entry
+      // instead. Note: A default visibility symbol is by default preemptible
+      // during linking, and should not be referenced with PC-relative
+      // relocations. Therefore, use a PLT relocation even if the function is
+      // dso_local.
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yozhu wrote:

I was referring to the logic in this [function](https://github.com/llvm/llvm-project/blob/main/llvm/lib/MC/ELFObjectWriter.cpp#L1365), where if it is PREL32 and the target symbol is dso_local, we may update relocation target from "func + vtable_slot_offset" to "section + offset". So if the dso_local function is not referenced elsewhere, we can omit its emission in local symtab.

https://github.com/llvm/llvm-project/pull/134781