Revert "AsmPrinter: Remove ELF's special lowerRelativeReference for unnamed_addr function"

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -125,6 +125,10 @@ class TargetLoweringObjectFileELF : public TargetLoweringObjectFile {
   lowerSymbolDifference(const MCSymbol *LHS, const MCSymbol *RHS,
                         int64_t Addend,
                         std::optional<int64_t> PCRelativeOffset) const;
+  const MCExpr *lowerRelativeReference(const GlobalValue *LHS,
+                                       const GlobalValue *RHS, int64_t Addend,
+                                       std::optional<int64_t> PCRelativeOffset,
+                                       const TargetMachine &TM) const override;
 
   const MCExpr *lowerDSOLocalEquivalent(const MCSymbol *LHS,
                                         const MCSymbol *RHS, int64_t Addend,

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -1233,6 +1233,24 @@ const MCExpr *TargetLoweringObjectFileELF::lowerSymbolDifference(
   return Res;
 }
 
+const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
+    const GlobalValue *LHS, const GlobalValue *RHS, int64_t Addend,
+    std::optional<int64_t> PCRelativeOffset, const TargetMachine &TM) const {
+  // We may only use a PLT-relative relocation to refer to unnamed_addr
+  // functions.
+  if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
+    return nullptr;
+
+  // Basic correctness checks.
+  if (LHS->getType()->getPointerAddressSpace() != 0 ||
+      RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
+      RHS->isThreadLocal())
+    return nullptr;
+
+  return lowerSymbolDifference(TM.getSymbol(LHS), TM.getSymbol(RHS), Addend,
+                               PCRelativeOffset);
+}
+
 // Reference the PLT entry of a function, optionally with a subtrahend (`RHS`).
 const MCExpr *TargetLoweringObjectFileELF::lowerDSOLocalEquivalent(
     const MCSymbol *LHS, const MCSymbol *RHS, int64_t Addend,

llvm/test/CodeGen/ARM/relative-reloc.ll → llvm/test/CodeGen/ARM/plt-relative-reloc.ll

@@ -10,8 +10,7 @@ declare void @fn1() unnamed_addr
 declare void @fn2() unnamed_addr
 declare void @fn3()
 
-;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
 ; CHECK: .long 0
-; CHECK-NEXT: .long fn1-vtable-4
-; CHECK-NEXT: .long fn2-vtable-4
+; CHECK-NEXT: .long fn1(prel31)-vtable-4
+; CHECK-NEXT: .long fn2(prel31)-vtable-4
 ; CHECK-NEXT: .long fn3-vtable-4

llvm/test/CodeGen/RISCV/relative-reloc.ll → llvm/test/CodeGen/RISCV/plt-relative-reloc.ll

@@ -12,11 +12,10 @@ declare void @fn2() unnamed_addr
 declare void @fn3()
 @global4 = external unnamed_addr global i8
 
-;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
 ; CHECK:      vtable:
 ; CHECK-NEXT:         .word   0                               # 0x0
-; CHECK-NEXT:         .word   fn1-vtable-4
-; CHECK-NEXT:         .word   fn2-vtable-4
+; CHECK-NEXT:         .word   %pltpcrel(fn1)
+; CHECK-NEXT:         .word   %pltpcrel(fn2+4)
 ; CHECK-NEXT:         .word   fn3-vtable-4
 ; CHECK-NEXT:         .word   global4-vtable-4
 ; CHECK-NEXT:         .size   vtable, 20

llvm/test/CodeGen/X86/relative-reloc-64.ll → llvm/test/CodeGen/X86/x86-64-plt-relative-reloc.ll

@@ -12,9 +12,8 @@ declare void @fn2() unnamed_addr
 declare void @fn3()
 @global4 = external unnamed_addr global i8
 
-;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
 ; CHECK: .long 0
-; CHECK-NEXT: .long fn1-vtable-4
-; CHECK-NEXT: .long fn2-vtable-4
+; CHECK-NEXT: .long fn1@PLT-vtable-4
+; CHECK-NEXT: .long fn2@PLT-vtable-4
 ; CHECK-NEXT: .long fn3-vtable-4
 ; CHECK-NEXT: .long global4-vtable-4

llvm/test/CodeGen/X86/relative-reloc-32.ll → llvm/test/CodeGen/X86/x86-plt-relative-reloc.ll

@@ -11,6 +11,6 @@ declare void @fn2() unnamed_addr
 declare void @fn3()
 
 ; CHECK: .long 0
-; CHECK-NEXT: .long fn1-vtable-4
-; CHECK-NEXT: .long fn2-vtable-4
+; CHECK-NEXT: .long fn1@PLT-vtable-4
+; CHECK-NEXT: .long fn2@PLT-vtable-4
 ; CHECK-NEXT: .long fn3-vtable-4