rustc: Start implementing compat with LLVM 9

This commit doesn't actually migrate to LLVM 9, but it brings our own
C++ bindings in line with LLVM 9 and able to compile against tip of
tree. The changes made were:

* The `MainSubprogram` flag for debuginfo moved between flag types.
* Iteration of archive members was tweaked slightly and we have to
  construct the two iterators before constructing the returned
  `RustArchiveIterator` value.
* The `getOrInsertFunction` binding now returns a wrapper which we use
  `getCallee()` on to get the value we're interested in.

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -296,12 +296,6 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         let mut flags = DIFlags::FlagPrototyped;
 
-        if let Some((id, _)) = self.tcx.entry_fn(LOCAL_CRATE) {
-            if id == def_id {
-                flags |= DIFlags::FlagMainSubprogram;
-            }
-        }
-
         if self.layout_of(sig.output()).abi.is_uninhabited() {
             flags |= DIFlags::FlagNoReturn;
         }
@@ -313,6 +307,11 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         if self.sess().opts.optimize != config::OptLevel::No {
             spflags |= DISPFlags::SPFlagOptimized;
         }
+        if let Some((id, _)) = self.tcx.entry_fn(LOCAL_CRATE) {
+            if id == def_id {
+                spflags |= DISPFlags::SPFlagMainSubprogram;
+            }
+        }
 
         let fn_metadata = unsafe {
             llvm::LLVMRustDIBuilderCreateFunction(

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -588,7 +588,6 @@ pub mod debuginfo {
             const FlagIntroducedVirtual   = (1 << 18);
             const FlagBitField            = (1 << 19);
             const FlagNoReturn            = (1 << 20);
-            const FlagMainSubprogram      = (1 << 21);
         }
     }
 
@@ -603,6 +602,7 @@ pub mod debuginfo {
             const SPFlagLocalToUnit       = (1 << 2);
             const SPFlagDefinition        = (1 << 3);
             const SPFlagOptimized         = (1 << 4);
+            const SPFlagMainSubprogram    = (1 << 5);
         }
     }
 

src/rustllvm/ArchiveWrapper.cpp

@@ -24,9 +24,14 @@ struct RustArchiveIterator {
   bool First;
   Archive::child_iterator Cur;
   Archive::child_iterator End;
-  Error Err;
+  std::unique_ptr<Error> Err;
 
-  RustArchiveIterator() : First(true), Err(Error::success()) {}
+  RustArchiveIterator(Archive::child_iterator Cur, Archive::child_iterator End,
+      std::unique_ptr<Error> Err)
+    : First(true),
+      Cur(Cur),
+      End(End),
+      Err(std::move(Err)) {}
 };
 
 enum class LLVMRustArchiveKind {
@@ -84,15 +89,14 @@ extern "C" void LLVMRustDestroyArchive(LLVMRustArchiveRef RustArchive) {
 extern "C" LLVMRustArchiveIteratorRef
 LLVMRustArchiveIteratorNew(LLVMRustArchiveRef RustArchive) {
   Archive *Archive = RustArchive->getBinary();
-  RustArchiveIterator *RAI = new RustArchiveIterator();
+  std::unique_ptr<Error> Err = llvm::make_unique<Error>(Error::success());
-  RAI->Cur = Archive->child_begin(RAI->Err);
+  auto Cur = Archive->child_begin(*Err);
-  if (RAI->Err) {
+  if (*Err) {
-    LLVMRustSetLastError(toString(std::move(RAI->Err)).c_str());
+    LLVMRustSetLastError(toString(std::move(*Err)).c_str());
-    delete RAI;
     return nullptr;
   }
-  RAI->End = Archive->child_end();
+  auto End = Archive->child_end();
-  return RAI;
+  return new RustArchiveIterator(Cur, End, std::move(Err));
 }
 
 extern "C" LLVMRustArchiveChildConstRef
@@ -108,8 +112,8 @@ LLVMRustArchiveIteratorNext(LLVMRustArchiveIteratorRef RAI) {
   // but instead advance it *before* fetching the child in all later calls.
   if (!RAI->First) {
     ++RAI->Cur;
-    if (RAI->Err) {
+    if (*RAI->Err) {
-      LLVMRustSetLastError(toString(std::move(RAI->Err)).c_str());
+      LLVMRustSetLastError(toString(std::move(*RAI->Err)).c_str());
       return nullptr;
     }
   } else {

src/rustllvm/RustWrapper.cpp

@@ -117,7 +117,11 @@ extern "C" LLVMValueRef LLVMRustGetOrInsertFunction(LLVMModuleRef M,
                                                     const char *Name,
                                                     LLVMTypeRef FunctionTy) {
   return wrap(
-      unwrap(M)->getOrInsertFunction(Name, unwrap<FunctionType>(FunctionTy)));
+      unwrap(M)->getOrInsertFunction(Name, unwrap<FunctionType>(FunctionTy))
+#if LLVM_VERSION_GE(9, 0)
+      .getCallee()
+#endif
+      );
 }
 
 extern "C" LLVMValueRef
@@ -417,7 +421,6 @@ enum class LLVMRustDIFlags : uint32_t {
   FlagIntroducedVirtual = (1 << 18),
   FlagBitField = (1 << 19),
   FlagNoReturn = (1 << 20),
-  FlagMainSubprogram = (1 << 21),
   // Do not add values that are not supported by the minimum LLVM
   // version we support! see llvm/include/llvm/IR/DebugInfoFlags.def
 };
@@ -508,9 +511,6 @@ static DINode::DIFlags fromRust(LLVMRustDIFlags Flags) {
   if (isSet(Flags & LLVMRustDIFlags::FlagNoReturn)) {
     Result |= DINode::DIFlags::FlagNoReturn;
   }
-  if (isSet(Flags & LLVMRustDIFlags::FlagMainSubprogram)) {
-    Result |= DINode::DIFlags::FlagMainSubprogram;
-  }
 
   return Result;
 }
@@ -525,6 +525,7 @@ enum class LLVMRustDISPFlags : uint32_t {
   SPFlagLocalToUnit = (1 << 2),
   SPFlagDefinition = (1 << 3),
   SPFlagOptimized = (1 << 4),
+  SPFlagMainSubprogram = (1 << 5),
   // Do not add values that are not supported by the minimum LLVM
   // version we support! see llvm/include/llvm/IR/DebugInfoFlags.def
   // (In LLVM < 8, createFunction supported these as separate bool arguments.)
@@ -575,6 +576,11 @@ static DISubprogram::DISPFlags fromRust(LLVMRustDISPFlags SPFlags) {
   if (isSet(SPFlags & LLVMRustDISPFlags::SPFlagOptimized)) {
     Result |= DISubprogram::DISPFlags::SPFlagOptimized;
   }
+#if LLVM_VERSION_GE(9, 0)
+  if (isSet(SPFlags & LLVMRustDISPFlags::SPFlagMainSubprogram)) {
+    Result |= DISubprogram::DISPFlags::SPFlagMainSubprogram;
+  }
+#endif
 
   return Result;
 }
@@ -671,18 +677,27 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateFunction(
   DITemplateParameterArray TParams =
       DITemplateParameterArray(unwrap<MDTuple>(TParam));
 #if LLVM_VERSION_GE(8, 0)
+  DISubprogram::DISPFlags llvmSPFlags = fromRust(SPFlags);
+  DINode::DIFlags llvmFlags = fromRust(Flags);
+#if LLVM_VERSION_LT(9, 0)
+  if (isSet(SPFlags & LLVMRustDISPFlags::SPFlagMainSubprogram))
+    llvmFlags |= DINode::DIFlags::FlagMainSubprogram;
+#endif
   DISubprogram *Sub = Builder->createFunction(
       unwrapDI<DIScope>(Scope), Name, LinkageName, unwrapDI<DIFile>(File),
-      LineNo, unwrapDI<DISubroutineType>(Ty), ScopeLine, fromRust(Flags),
+      LineNo, unwrapDI<DISubroutineType>(Ty), ScopeLine, llvmFlags,
-      fromRust(SPFlags), TParams, unwrapDIPtr<DISubprogram>(Decl));
+      llvmSPFlags, TParams, unwrapDIPtr<DISubprogram>(Decl));
 #else
   bool IsLocalToUnit = isSet(SPFlags & LLVMRustDISPFlags::SPFlagLocalToUnit);
   bool IsDefinition = isSet(SPFlags & LLVMRustDISPFlags::SPFlagDefinition);
   bool IsOptimized = isSet(SPFlags & LLVMRustDISPFlags::SPFlagOptimized);
+  DINode::DIFlags llvmFlags = fromRust(Flags);
+  if (isSet(SPFlags & LLVMRustDISPFlags::SPFlagMainSubprogram))
+    llvmFlags |= DINode::DIFlags::FlagMainSubprogram;
   DISubprogram *Sub = Builder->createFunction(
       unwrapDI<DIScope>(Scope), Name, LinkageName, unwrapDI<DIFile>(File),
       LineNo, unwrapDI<DISubroutineType>(Ty), IsLocalToUnit, IsDefinition,
-      ScopeLine, fromRust(Flags), IsOptimized, TParams,
+      ScopeLine, llvmFlags, IsOptimized, TParams,
       unwrapDIPtr<DISubprogram>(Decl));
 #endif
   unwrap<Function>(Fn)->setSubprogram(Sub);