debuginfo: Fix issue with unique type IDs not being passed to LLVM for LLVM 3.4

Author: michaelwoerister

src/librustc/lib/llvm.rs

@@ -1809,6 +1809,7 @@ pub mod llvm {
         pub fn LLVMRustDestroyArchive(AR: ArchiveRef);
 
         pub fn LLVMRustSetDLLExportStorageClass(V: ValueRef);
+        pub fn LLVMVersionMajor() -> c_int;
         pub fn LLVMVersionMinor() -> c_int;
 
         pub fn LLVMRustGetSectionName(SI: SectionIteratorRef,

src/librustc/middle/trans/debuginfo.rs

@@ -179,7 +179,6 @@ use std::collections::HashSet;
 use std::gc::Gc;
 use std::ptr;
 use std::rc::{Rc, Weak};
-use std::sync::atomics;
 use syntax::util::interner::Interner;
 use syntax::codemap::{Span, Pos};
 use syntax::{abi, ast, codemap, ast_util, ast_map};
@@ -2356,9 +2355,22 @@ fn set_members_of_composite_type(cx: &CrateContext,
         let mut composite_types_completed =
             debug_context(cx).composite_types_completed.borrow_mut();
         if composite_types_completed.contains(&composite_type_metadata) {
-            cx.sess().span_bug(definition_span, "debuginfo::set_members_of_composite_type() - \
-                                                 Already completed forward declaration \
-                                                 re-encountered.");
+            let (llvm_version_major, llvm_version_minor) = unsafe {
+                (llvm::LLVMVersionMajor(), llvm::LLVMVersionMinor())
+            };
+
+            let actual_llvm_version = llvm_version_major * 1000000 + llvm_version_minor * 1000;
+            let min_supported_llvm_version = 3 * 1000000 + 4 * 1000;
+
+            if actual_llvm_version < min_supported_llvm_version {
+                cx.sess().warn(format!("This version of rustc was built with LLVM {}.{}. \
+                    Rustc just ran into a known debuginfo corruption problem that \
+                    often occurs with LLVM versions below 3.4. Please use a rustc built with a \
+                    newer version of LLVM.", llvm_version_major, llvm_version_minor).as_slice());
+            } else {
+                cx.sess().bug("debuginfo::set_members_of_composite_type() - \
+                               Already completed forward declaration re-encountered.");
+            }
         } else {
             composite_types_completed.insert(composite_type_metadata);
         }

src/rustllvm/RustWrapper.cpp

@@ -318,7 +318,7 @@ extern "C" LLVMValueRef LLVMDIBuilderCreateStructType(
         unwrapDI<DIArray>(Elements),
         RunTimeLang,
         unwrapDI<DIType>(VTableHolder)
-#if LLVM_VERSION_MINOR >= 5
+#if LLVM_VERSION_MINOR >= 4
         ,UniqueId
 #endif
         ));
@@ -510,7 +510,7 @@ extern "C" LLVMValueRef LLVMDIBuilderCreateUnionType(
         Flags,
         unwrapDI<DIArray>(Elements),
         RunTimeLang
-#if LLVM_VERSION_MINOR >= 5
+#if LLVM_VERSION_MINOR >= 4
         ,UniqueId
 #endif
         ));
@@ -734,6 +734,11 @@ LLVMVersionMinor() {
     return LLVM_VERSION_MINOR;
 }
 
+extern "C" int
+LLVMVersionMajor() {
+    return LLVM_VERSION_MAJOR;
+}
+
 // Note that the two following functions look quite similar to the
 // LLVMGetSectionName function. Sadly, it appears that this function only
 // returns a char* pointer, which isn't guaranteed to be null-terminated. The