Auto merge of #38156 - shepmaster:llvm-4.0-bitcode-reader-writer, r=alexcrichton

[LLVM 4.0] New bitcode headers and API

/cc @michaelwoerister @rkruppe

Author: bors

src/rustllvm/RustWrapper.cpp

@@ -892,19 +892,34 @@ extern "C" void LLVMRustWriteValueToString(LLVMValueRef Value, RustStringRef str
 extern "C" bool
 LLVMRustLinkInExternalBitcode(LLVMModuleRef dst, char *bc, size_t len) {
     Module *Dst = unwrap(dst);
+
     std::unique_ptr<MemoryBuffer> buf = MemoryBuffer::getMemBufferCopy(StringRef(bc, len));
+
+#if LLVM_VERSION_GE(4, 0)
+    Expected<std::unique_ptr<Module>> SrcOrError =
+        llvm::getLazyBitcodeModule(buf->getMemBufferRef(), Dst->getContext());
+    if (!SrcOrError) {
+        LLVMRustSetLastError(toString(SrcOrError.takeError()).c_str());
+        return false;
+    }
+
+    auto Src = std::move(*SrcOrError);
+#else
     ErrorOr<std::unique_ptr<Module>> Src =
         llvm::getLazyBitcodeModule(std::move(buf), Dst->getContext());
     if (!Src) {
         LLVMRustSetLastError(Src.getError().message().c_str());
         return false;
     }
+#endif
 
     std::string Err;
 
     raw_string_ostream Stream(Err);
     DiagnosticPrinterRawOStream DP(Stream);
-#if LLVM_VERSION_GE(3, 8)
+#if LLVM_VERSION_GE(4, 0)
+    if (Linker::linkModules(*Dst, std::move(Src))) {
+#elif LLVM_VERSION_GE(3, 8)
     if (Linker::linkModules(*Dst, std::move(Src.get()))) {
 #else
     if (Linker::LinkModules(Dst, Src->get(), [&](const DiagnosticInfo &DI) { DI.print(DP); })) {

src/rustllvm/rustllvm.h

@@ -39,7 +39,6 @@
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/Vectorize.h"
-#include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm-c/Core.h"
 #include "llvm-c/BitReader.h"
 #include "llvm-c/ExecutionEngine.h"
@@ -60,6 +59,13 @@
 #include "llvm/PassManager.h"
 #endif
 
+#if LLVM_VERSION_GE(4, 0)
+#include "llvm/Bitcode/BitcodeReader.h"
+#include "llvm/Bitcode/BitcodeWriter.h"
+#else
+#include "llvm/Bitcode/ReaderWriter.h"
+#endif
+
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DIBuilder.h"