WebAssembly: add logging when I get a BinaryExpr

I actually do need to know what's breaking.

Author: zhuowei

lib/MC/WasmObjectWriter.cpp

@@ -480,6 +480,10 @@ void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
     const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
     if (Inner && Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
       llvm_unreachable("weakref used in reloc not yet implemented");
+    if (!Inner) {
+      fprintf(stderr, "weak check failed to get an inner:\n");
+      Expr->dump();
+    }
   }
 
   // Put any constant offset in an addend. Offsets can be negative, and
@@ -585,6 +589,8 @@ static const MCSymbolWasm *ResolveSymbol(const MCSymbolWasm &Symbol) {
   if (Symbol.isVariable()) {
     const MCExpr *Expr = Symbol.getVariableValue();
     if (Expr->getKind() == MCExpr::Binary) {
+      fprintf(stderr, "ResolveSymbol got binary expr\n");
+      Expr->dump();
       Expr = pullSymbol(Expr);
       if (!Expr) {
         llvm_unreachable("can't find a symbol in binary expression\n");