[lld][WebAssembly] Fix spurious signature mismatch warnings

Summary:
This a follow up on: https://reviews.llvm.org/D62153

Handle the case where there are multiple object files that contain
undefined references to the same function.  We only generate a function
variant if the existing symbol is directly called.

See: https://github.com/emscripten-core/emscripten/issues/8995

Subscribers: dschuff, jgravelle-google, aheejin, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67015

llvm-svn: 370509

1 files changed, 9 insertions, 2 deletions

diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index c46eec41146..44417b076c7 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -425,9 +425,16 @@ Symbol *SymbolTable::addUndefinedFunction(StringRef name, StringRef importName,
     }
     if (!existingFunction->signature && sig)
       existingFunction->signature = sig;
-    if (isCalledDirectly && !signatureMatches(existingFunction, sig))
-      if (getFunctionVariant(s, sig, file, &s))
+    if (isCalledDirectly && !signatureMatches(existingFunction, sig)) {
+      auto* existingUndefined = dyn_cast<UndefinedFunction>(existingFunction);
+      // If the existing undefined functions is not called direcltly then let
+      // this one take precedence.  Otherwise the existing function is either
+      // direclty called or defined, in which case we need a function variant.
+      if (existingUndefined && !existingUndefined->isCalledDirectly)
         replaceSym();
+      else if (getFunctionVariant(s, sig, file, &s))
+        replaceSym();
+    }
   }
 
   return s;