commit 8b0b48f343cb0347e266f8b551425e5fa21ce948
author Sam Clegg <sbc@chromium.org> Fri Sep 28 16:50:14 2018 +0000
committer Sam Clegg <sbc@chromium.org> Fri Sep 28 16:50:14 2018 +0000
tree 75136cd60fb06efd2a4dd21af92524c6720ed2c0
parent e42a8ecf660b1244b1b573007c2fbf70042e02a4

[WebAssembly] Preserve function signatures during LTO

With LTO when and undefined function (with a known signature)
in replaced by a defined bitcode function we were loosing the
signature information (since bitcode functions don't have
signatures).

With this change we preserve the original signature from the
undefined function and verify that the post LTO compiled
function has the correct signature.

This change improves the error handling in the case where
there is a signature mismatch with a function defined in
a bitcode file.

Differential Revision: https://reviews.llvm.org/D50721

llvm-svn: 343340

lld/wasm/SymbolTable.cpp

diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index 2a4249e..d1e9c05 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -201,7 +201,9 @@
 Symbol *SymbolTable::addDefinedFunction(StringRef Name, uint32_t Flags,
                                         InputFile *File,
                                         InputFunction *Function) {
-  LLVM_DEBUG(dbgs() << "addDefinedFunction: " << Name << "\n");
+  LLVM_DEBUG(dbgs() << "addDefinedFunction: " << Name << " ["
+                    << (Function ? toString(Function->Signature) : "none")
+                    << "]\n");
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name, File);
@@ -214,8 +216,16 @@
   if (Function)
     checkFunctionType(S, File, &Function->Signature);
 
-  if (shouldReplace(S, File, Flags))
-    replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
+  if (shouldReplace(S, File, Flags)) {
+    // If the new defined function doesn't have signture (i.e. bitcode
+    // functions) but the old symbols does then preserve the old signature
+    const WasmSignature *OldSig = nullptr;
+    if (auto* F = dyn_cast<FunctionSymbol>(S))
+      OldSig = F->FunctionType;
+    auto NewSym = replaceSymbol<DefinedFunction>(S, Name, Flags, File, Function);
+    if (!NewSym->FunctionType)
+      NewSym->FunctionType = OldSig;
+  }
   return S;
 }
 
@@ -263,7 +273,8 @@
 Symbol *SymbolTable::addUndefinedFunction(StringRef Name, uint32_t Flags,
                                           InputFile *File,
                                           const WasmSignature *Sig) {
-  LLVM_DEBUG(dbgs() << "addUndefinedFunction: " << Name << "\n");
+  LLVM_DEBUG(dbgs() << "addUndefinedFunction: " << Name <<
+             " [" << (Sig ? toString(*Sig) : "none") << "]\n");
 
   Symbol *S;
   bool WasInserted;