[lld] r347909 - [WebAssembly] Allow undefined symbols when building shared libraries

[Sam Clegg via llvm-commits]

Author: sbc
Date: Thu Nov 29 12:07:13 2018
New Revision: 347909

URL: http://llvm.org/viewvc/llvm-project?rev=347909&view=rev
Log:
[WebAssembly] Allow undefined symbols when building shared libraries

Differential Revision: https://reviews.llvm.org/D55043

Modified:
    lld/trunk/test/wasm/shared.ll
    lld/trunk/wasm/Driver.cpp

Modified: lld/trunk/test/wasm/shared.ll
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/wasm/shared.ll?rev=347909&r1=347908&r2=347909&view=diff
==============================================================================
--- lld/trunk/test/wasm/shared.ll (original)
+++ lld/trunk/test/wasm/shared.ll Thu Nov 29 12:07:13 2018
@@ -4,27 +4,34 @@
 
 target triple = "wasm32-unknown-unknown"
 
- at used_data = hidden global i32 2, align 4
+ at data = hidden global i32 2, align 4
 @indirect_func = local_unnamed_addr global void ()* @foo, align 4
+ at indirect_func_external = local_unnamed_addr global void ()* @func_external, align 4
 
 define default void @foo() {
 entry:
   ; To ensure we use __stack_pointer
   %ptr = alloca i32
-  %0 = load i32, i32* @used_data, align 4
-  %1 = load void ()*, void ()** @indirect_func, align 4
-  call void %1()
+  %0 = load i32, i32* @data, align 4
+  %1 = load i32, i32* @data_external, align 4
+  %2 = load void ()*, void ()** @indirect_func, align 4
+  call void %2()
   ret void
 }
 
+declare void @func_external()
+
+ at data_external = external global i32
+
+
 ; check for dylink section at start
 
 ; CHECK:      Sections:
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            dylink
-; CHECK-NEXT:     MemorySize:      4
+; CHECK-NEXT:     MemorySize:      8
 ; CHECK-NEXT:     MemoryAlignment: 2
-; CHECK-NEXT:     TableSize:       1
+; CHECK-NEXT:     TableSize:       2
 ; CHECK-NEXT:     TableAlignment:  0
 
 ; check for import of __table_base and __memory_base globals
@@ -38,8 +45,8 @@ entry:
 ; CHECK-NEXT:           ElemType:        ANYFUNC
 ; CHECK-NEXT:           Limits:
 ; CHECK-NEXT:             Flags:           [ HAS_MAX ]
-; CHECK-NEXT:             Initial:         0x00000001
-; CHECK-NEXT:             Maximum:         0x00000001
+; CHECK-NEXT:             Initial:         0x00000002
+; CHECK-NEXT:             Maximum:         0x00000002
 ; CHECK-NEXT:       - Module:          env
 ; CHECK-NEXT:         Field:           __stack_pointer
 ; CHECK-NEXT:         Kind:            GLOBAL
@@ -63,7 +70,7 @@ entry:
 ; CHECK-NEXT:       - Offset:
 ; CHECK-NEXT:           Opcode:          GET_GLOBAL
 ; CHECK-NEXT:           Index:           2
-; CHECK-NEXT:         Functions:       [ 1 ]
+; CHECK-NEXT:         Functions:       [ 2, 0 ]
 
 ; check the data segment initialized with __memory_base global as offset
 
@@ -74,4 +81,4 @@ entry:
 ; CHECK-NEXT:         Offset:
 ; CHECK-NEXT:           Opcode:          GET_GLOBAL
 ; CHECK-NEXT:           Index:           1
-; CHECK-NEXT:         Content:         '00000000'
+; CHECK-NEXT:         Content:         '0000000001000000'

Modified: lld/trunk/wasm/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Driver.cpp?rev=347909&r1=347908&r2=347909&view=diff
==============================================================================
--- lld/trunk/wasm/Driver.cpp (original)
+++ lld/trunk/wasm/Driver.cpp Thu Nov 29 12:07:13 2018
@@ -313,8 +313,7 @@ static void handleWeakUndefines() {
     // be GC'd if not used as the target of any "call" instructions.
     std::string SymName = toString(*Sym);
     StringRef DebugName = Saver.save("undefined function " + SymName);
-    SyntheticFunction *Func =
-        make<SyntheticFunction>(Sig, Sym->getName(), DebugName);
+    auto *Func = make<SyntheticFunction>(Sig, Sym->getName(), DebugName);
     Func->setBody(UnreachableFn);
     // Ensure it compares equal to the null pointer, and so that table relocs
     // don't pull in the stub body (only call-operand relocs should do that).
@@ -448,9 +447,10 @@ static void createSyntheticSymbols() {
   static llvm::wasm::WasmGlobalType MutableGlobalTypeI32 = {WASM_TYPE_I32,
                                                             true};
 
-  WasmSym::CallCtors = Symtab->addSyntheticFunction(
-      "__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
-      make<SyntheticFunction>(NullSignature, "__wasm_call_ctors"));
+  if (!Config->Relocatable)
+    WasmSym::CallCtors = Symtab->addSyntheticFunction(
+        "__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
+        make<SyntheticFunction>(NullSignature, "__wasm_call_ctors"));
 
   // The __stack_pointer is imported in the shared library case, and exported
   // in the non-shared (executable) case.
@@ -463,7 +463,7 @@ static void createSyntheticSymbols() {
     Global.InitExpr.Value.Int32 = 0;
     Global.InitExpr.Opcode = WASM_OPCODE_I32_CONST;
     Global.SymbolName = "__stack_pointer";
-    InputGlobal *StackPointer = make<InputGlobal>(Global, nullptr);
+    auto *StackPointer = make<InputGlobal>(Global, nullptr);
     StackPointer->Live = true;
     // For non-PIC code
     // TODO(sbc): Remove WASM_SYMBOL_VISIBILITY_HIDDEN when the mutable global
@@ -543,8 +543,10 @@ void LinkerDriver::link(ArrayRef<const c
     Config->ImportTable = true;
   }
 
-  if (Config->Shared)
+  if (Config->Shared) {
     Config->ExportDynamic = true;
+    Config->AllowUndefined = true;
+  }
 
   if (!Config->Relocatable)
     createSyntheticSymbols();