rustc_trans: do not emit !range/!nonnull for LLVM older than 3.9, to work around rust-lang#36023.

Author: eddyb

src/librustc_trans/builder.rs

@@ -544,6 +544,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
 
     pub fn range_metadata(&self, load: ValueRef, range: Range<u128>) {
+        if !self.ccx.use_range_or_nonnull_metadata() {
+            return;
+        }
         unsafe {
             let llty = val_ty(load);
             let v = [
@@ -559,6 +562,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     }
 
     pub fn nonnull_metadata(&self, load: ValueRef) {
+        if !self.ccx.use_range_or_nonnull_metadata() {
+            return;
+        }
         unsafe {
             llvm::LLVMSetMetadata(load, llvm::MD_nonnull as c_uint,
                                   llvm::LLVMMDNodeInContext(self.ccx.llcx(), ptr::null(), 0));

src/librustc_trans/context.rs

@@ -53,6 +53,10 @@ pub struct SharedCrateContext<'a, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     check_overflow: bool,
     use_dll_storage_attrs: bool,
+
+    // HACK(eddyb) remove this after we make the required LLVM version 3.9
+    // or later. See issue #36023 and PR #45225 for more details on the bug.
+    use_range_or_nonnull_metadata: bool,
 }
 
 /// The local portion of a `CrateContext`.  There is one `LocalCrateContext`
@@ -284,10 +288,16 @@ impl<'b, 'tcx> SharedCrateContext<'b, 'tcx> {
 
         let check_overflow = tcx.sess.overflow_checks();
 
+        // See the comment on the `use_range_or_nonnull_metadata` field.
+        let use_range_or_nonnull_metadata = unsafe {
+            (llvm::LLVMRustVersionMajor(), llvm::LLVMRustVersionMinor()) >= (3, 9)
+        };
+
         SharedCrateContext {
             tcx,
             check_overflow,
             use_dll_storage_attrs,
+            use_range_or_nonnull_metadata,
         }
     }
 
@@ -524,6 +534,10 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
         self.shared.use_dll_storage_attrs()
     }
 
+    pub fn use_range_or_nonnull_metadata(&self) -> bool {
+        self.shared.use_range_or_nonnull_metadata
+    }
+
     /// Generate a new symbol name with the given prefix. This symbol name must
     /// only be used for definitions with `internal` or `private` linkage.
     pub fn generate_local_symbol_name(&self, prefix: &str) -> String {

src/test/codegen/loads.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // compile-flags: -C no-prepopulate-passes
+// min-llvm-version 3.9
 
 #![crate_type = "lib"]
 

src/test/run-pass/issue-36023.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// min-llvm-version 3.9
-
 use std::ops::Deref;
 
 fn main() {