[WebAssembly][lld] --importTable flag only imports table if needed

Before, --importTable forced the creation of an indirect function table,
whether it was needed or not.  Now it only imports a table if needed.

Differential Revision: https://reviews.llvm.org/D96872

2 files changed, 10 insertions, 20 deletions

diff --git a/lld/test/wasm/import-table.test b/lld/test/wasm/import-table.test
index 462264d..088ff12 100644
--- a/lld/test/wasm/import-table.test
+++ b/lld/test/wasm/import-table.test
@@ -1,7 +1,15 @@
 # RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/start.s -o %t.start.o
-# RUN: wasm-ld --import-table -o %t.wasm %t.start.o
+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
+# RUN: wasm-ld --export-all --import-table -o %t.wasm %t.start.o %t.o
 # RUN: obj2yaml %t.wasm | FileCheck %s
 
+.globl require_function_table
+require_function_table:
+.functype require_function_table () -> ()
+          i32.const 1
+          call_indirect () -> ()
+          end_function
+
 # Verify the --import-table flag creates a table import
 
 # CHECK:       - Type:            IMPORT
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
index a3bcfb7..7e647cb 100644
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -799,21 +799,6 @@ static TableSymbol *createDefinedIndirectFunctionTable(StringRef name) {
   return sym;
 }
 
-static TableSymbol *createUndefinedIndirectFunctionTable(StringRef name) {
-  WasmLimits limits{0, 0, 0}; // Set by the writer.
-  WasmTableType *type = make<WasmTableType>();
-  type->ElemType = uint8_t(ValType::FUNCREF);
-  type->Limits = limits;
-  StringRef module(defaultModule);
-  uint32_t flags = config->exportTable ? 0 : WASM_SYMBOL_VISIBILITY_HIDDEN;
-  flags |= WASM_SYMBOL_UNDEFINED;
-  Symbol *sym =
-      symtab->addUndefinedTable(name, name, module, flags, nullptr, type);
-  sym->markLive();
-  sym->forceExport = config->exportTable;
-  return cast<TableSymbol>(sym);
-}
-
 static TableSymbol *resolveIndirectFunctionTable() {
   Symbol *existing = symtab->find(functionTableName);
   if (existing) {
@@ -830,10 +815,7 @@ static TableSymbol *resolveIndirectFunctionTable() {
   }
 
   if (config->importTable) {
-    if (existing)
-      return cast<TableSymbol>(existing);
-    else
-      return createUndefinedIndirectFunctionTable(functionTableName);
+    return cast_or_null<TableSymbol>(existing);
   } else if ((existing && existing->isLive()) || config->exportTable) {
     // A defined table is required.  Either because the user request an exported
     // table or because the table symbol is already live.  The existing table is