[WebAssembly] MC: Handle aliases of aliases

[sbc100]

Summary

Fixes PR40784

[sbc100]

• revert

[sbc100]

• rebase onto D58472

llvm/trunk/lib/MC/WasmObjectWriter.cpp

void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
   } else if (FixupSection.getKind().isMetadata()) {
     CustomSectionsRelocations[&FixupSection].push_back(Rec);
   } else {
     llvm_unreachable("unexpected section type");
   }
 }
 
 static const MCSymbolWasm *resolveSymbol(const MCSymbolWasm &Symbol) {
-  if (Symbol.isVariable()) {
-    const MCExpr *Expr = Symbol.getVariableValue();
+  const MCSymbolWasm* Ret = &Symbol;
+  while (Ret->isVariable()) {
+    const MCExpr *Expr = Ret->getVariableValue();
     auto *Inner = cast<MCSymbolRefExpr>(Expr);
-    return cast<MCSymbolWasm>(&Inner->getSymbol());
+    Ret = cast<MCSymbolWasm>(&Inner->getSymbol());
   }
-  return &Symbol;
+  return Ret;
 }
 
 // Compute a value to write into the code at the location covered
 // by RelEntry. This value isn't used by the static linker; it just serves
 // to make the object format more readable and more likely to be directly
 // useable.
 uint32_t
 WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry) {
for (const MCSymbol &S : Asm.symbols()) {
     assert(S.isDefined());
 
     // Find the target symbol of this weak alias and export that index
     const auto &WS = static_cast<const MCSymbolWasm &>(S);
     const MCSymbolWasm *ResolvedSym = resolveSymbol(WS);
     LLVM_DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *ResolvedSym
                       << "'\n");
 
-    if (WS.isFunction()) {
+    if (ResolvedSym->isFunction()) {
       assert(WasmIndices.count(ResolvedSym) > 0);
       uint32_t WasmIndex = WasmIndices.find(ResolvedSym)->second;
       WasmIndices[&WS] = WasmIndex;
       LLVM_DEBUG(dbgs() << "  -> index:" << WasmIndex << "\n");
-    } else if (WS.isData()) {
+    } else if (ResolvedSym->isData()) {
       assert(DataLocations.count(ResolvedSym) > 0);
       const wasm::WasmDataReference &Ref =
           DataLocations.find(ResolvedSym)->second;
       DataLocations[&WS] = Ref;
       LLVM_DEBUG(dbgs() << "  -> index:" << Ref.Segment << "\n");
     } else {
       report_fatal_error("don't yet support global/event aliases");
     }

llvm/trunk/test/MC/WebAssembly/function-alias.ll

 ; RUN: llc -filetype=obj %s -o - | llvm-readobj -symbols | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown-wasm"
 
 @foo = alias i8, bitcast (i8* ()* @func to i8*)
 @bar = alias i8* (), i8* ()* @func
+@bar2 = alias i8* (), i8* ()* @bar
 
 define i8* @func() {
+  call i8* @bar2();
   ret i8* @foo;
 }
 
 ; CHECK:      Symbols [
 ; CHECK-NEXT:   Symbol {
 ; CHECK-NEXT:     Name: func
 ; CHECK-NEXT:     Type: FUNCTION (0x0)
 ; CHECK-NEXT:     Flags [ (0x0)
 ; CHECK-NEXT:     ]
 ; CHECK-NEXT:     ElementIndex: 0x0
 ; CHECK-NEXT:   }
 ; CHECK-NEXT:   Symbol {
+; CHECK-NEXT:     Name: bar2
+; CHECK-NEXT:     Type: FUNCTION (0x0)
+; CHECK-NEXT:     Flags [ (0x0)
+; CHECK-NEXT:     ]
+; CHECK-NEXT:     ElementIndex: 0x0
+; CHECK-NEXT:   }
+; CHECK-NEXT:   Symbol {
 ; CHECK-NEXT:     Name: foo
 ; CHECK-NEXT:     Type: FUNCTION (0x0)
 ; CHECK-NEXT:     Flags [ (0x0)
 ; CHECK-NEXT:     ]
 ; CHECK-NEXT:     ElementIndex: 0x0
 ; CHECK-NEXT:   }
 ; CHECK-NEXT:   Symbol {
 ; CHECK-NEXT:     Name: bar
 ; CHECK-NEXT:     Type: FUNCTION (0x0)
 ; CHECK-NEXT:     Flags [ (0x0)
 ; CHECK-NEXT:     ]
 ; CHECK-NEXT:     ElementIndex: 0x0
 ; CHECK-NEXT:   }
 ; CHECK-NEXT: ]