[ExecutionEngine] Add weak symbol support to RuntimeDyld

Support weak symbols by first looking up if there is an externally visible symbol we can find,
and only if that fails using the one in the object file we're loading.

Reviewed By: lhames
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D6950

llvm-svn: 227228

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/unittests/ExecutionEngine/MCJIT/MCJITTest.cpp b/llvm/unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
index 64d8c2fca04..f9ca0fc8717 100644
--- a/llvm/unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
+++ b/llvm/unittests/ExecutionEngine/MCJIT/MCJITTest.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/MCJIT.h"
+#include "llvm/Support/DynamicLibrary.h"
 #include "MCJITTestBase.h"
 #include "gtest/gtest.h"
 
@@ -199,4 +200,45 @@ TEST_F(MCJITTest, multiple_decl_lookups) {
   EXPECT_EQ(A, B) << "Repeat calls to getPointerToFunction fail.";
 }
 
+// Test weak symbol linking when the weak symbol is present in a shared
+// library
+TEST_F(MCJITTest, weak_symbol_present) {
+  SKIP_UNSUPPORTED_PLATFORM;
+
+  int FakeWeakSymbol;
+  llvm::sys::DynamicLibrary::AddSymbol("FakeWeakSymbol", &FakeWeakSymbol);
+  createJITFromAssembly(
+  "$FakeWeakSymbol = comdat any\n"
+  "@FakeWeakSymbol = linkonce_odr global i32 42, comdat, align 4\n"
+  "define i32 @weak_test(i32* %arg) {\n"
+  "    %r = icmp eq i32* %arg, @FakeWeakSymbol\n"
+  "    %ret = zext i1 %r to i32\n"
+  "    ret i32 %ret\n"
+  "  }");
+
+  uint64_t Addr = TheJIT->getFunctionAddress("weak_test");;
+  EXPECT_TRUE(Addr != 0);
+  int32_t(*FuncPtr)(int32_t *) = (int32_t(*)(int32_t *))Addr;
+  EXPECT_EQ(FuncPtr(&FakeWeakSymbol),1);
+  EXPECT_TRUE(TheJIT->getGlobalValueAddress("FakeWeakSymbol") == 0);
+}
+
+// Test weak symbol linking when the weak symbol is not present in a
+// shared library
+TEST_F(MCJITTest, weak_symbol_absent) {
+  SKIP_UNSUPPORTED_PLATFORM;
+
+  SMDiagnostic Error;
+  createJITFromAssembly(
+  "  $FakeWeakSymbol2 = comdat any\n"
+  "  @FakeWeakSymbol2 = linkonce_odr global i32 42, comdat, align 4\n"
+  "  define i32* @get_weak() {\n"
+  "    ret i32* @FakeWeakSymbol2\n"
+  "  }\n");
+  void*(*FuncPtr)() =
+    (void*(*)(void))TheJIT->getFunctionAddress("get_weak");
+  EXPECT_EQ(FuncPtr(),(void*)TheJIT->getGlobalValueAddress("FakeWeakSymbol2"));
+}
+
+
 }