diff --git a/src/liballoc/collections/btree/node.rs b/src/liballoc/collections/btree/node.rs
index c1bd68a020a68..362755f8b7f63 100644
--- a/src/liballoc/collections/btree/node.rs
+++ b/src/liballoc/collections/btree/node.rs
@@ -1191,7 +1191,7 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::
         let right_len = right_node.len();
 
         // necessary for correctness, but in a private module
-        assert!(left_len + right_len + 1 <= CAPACITY);
+        assert!(left_len + right_len < CAPACITY);
 
         unsafe {
             ptr::write(
diff --git a/src/libcore/iter/adapters/mod.rs b/src/libcore/iter/adapters/mod.rs
index 58606531a1ace..02dc9b8f82ed2 100644
--- a/src/libcore/iter/adapters/mod.rs
+++ b/src/libcore/iter/adapters/mod.rs
@@ -1894,9 +1894,7 @@ where
             let to_skip = self.n;
             self.n = 0;
             // nth(n) skips n+1
-            if self.iter.nth(to_skip - 1).is_none() {
-                return None;
-            }
+            self.iter.nth(to_skip - 1)?;
         }
         self.iter.nth(n)
     }
@@ -1916,9 +1914,7 @@ where
     fn last(mut self) -> Option<I::Item> {
         if self.n > 0 {
             // nth(n) skips n+1
-            if self.iter.nth(self.n - 1).is_none() {
-                return None;
-            }
+            self.iter.nth(self.n - 1)?;
         }
         self.iter.last()
     }
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index 4f7c4153ea173..bd26e02efb749 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -338,9 +338,8 @@ impl<'hir> Map<'hir> {
             Node::Variant(_) => DefKind::Variant,
             Node::Ctor(variant_data) => {
                 // FIXME(eddyb) is this even possible, if we have a `Node::Ctor`?
-                if variant_data.ctor_hir_id().is_none() {
-                    return None;
-                }
+                variant_data.ctor_hir_id()?;
+
                 let ctor_of = match self.find(self.get_parent_node(hir_id)) {
                     Some(Node::Item(..)) => def::CtorOf::Struct,
                     Some(Node::Variant(..)) => def::CtorOf::Variant,
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 668240ab42b4c..36818020569b0 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -189,7 +189,7 @@ impl<'tcx> Body<'tcx> {
     ) -> Self {
         // We need `arg_count` locals, and one for the return place.
         assert!(
-            local_decls.len() >= arg_count + 1,
+            local_decls.len() > arg_count,
             "expected at least {} locals, got {}",
             arg_count + 1,
             local_decls.len()
diff --git a/src/librustc/ty/instance.rs b/src/librustc/ty/instance.rs
index f65822aba4c9e..4014d1d8ae250 100644
--- a/src/librustc/ty/instance.rs
+++ b/src/librustc/ty/instance.rs
@@ -115,9 +115,7 @@ impl<'tcx> Instance<'tcx> {
         }
 
         // If this a non-generic instance, it cannot be a shared monomorphization.
-        if self.substs.non_erasable_generics().next().is_none() {
-            return None;
-        }
+        self.substs.non_erasable_generics().next()?;
 
         match self.def {
             InstanceDef::Item(def_id) => tcx
diff --git a/src/librustc_codegen_llvm/va_arg.rs b/src/librustc_codegen_llvm/va_arg.rs
index 9bc3eec60ae04..a552f2cdb78aa 100644
--- a/src/librustc_codegen_llvm/va_arg.rs
+++ b/src/librustc_codegen_llvm/va_arg.rs
@@ -117,8 +117,7 @@ pub(super) fn emit_va_arg(
         // Windows x86_64
         ("x86_64", true) => {
             let target_ty_size = bx.cx.size_of(target_ty).bytes();
-            let indirect =
-                if target_ty_size > 8 || !target_ty_size.is_power_of_two() { true } else { false };
+            let indirect: bool = target_ty_size > 8 || !target_ty_size.is_power_of_two();
             emit_ptr_va_arg(bx, addr, target_ty, indirect, Align::from_bytes(8).unwrap(), false)
         }
         // For all other architecture/OS combinations fall back to using
diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs
index 847b5b81d5adc..0dd2f029e8d32 100644
--- a/src/librustc_codegen_ssa/back/link.rs
+++ b/src/librustc_codegen_ssa/back/link.rs
@@ -186,7 +186,7 @@ pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathB
     if flavor == LinkerFlavor::Msvc && t.target_vendor == "uwp" {
         if let Some(ref tool) = msvc_tool {
             let original_path = tool.path();
-            if let Some(ref root_lib_path) = original_path.ancestors().skip(4).next() {
+            if let Some(ref root_lib_path) = original_path.ancestors().nth(4) {
                 let arch = match t.arch.as_str() {
                     "x86_64" => Some("x64".to_string()),
                     "x86" => Some("x86".to_string()),
diff --git a/src/librustc_error_codes/error_codes/E0379.md b/src/librustc_error_codes/error_codes/E0379.md
index 3503da6ac2f78..930204847ecd8 100644
--- a/src/librustc_error_codes/error_codes/E0379.md
+++ b/src/librustc_error_codes/error_codes/E0379.md
@@ -1,3 +1,15 @@
+A trait method was declared const.
+
+Erroneous code example:
+
+```compile_fail,E0379
+#![feature(const_fn)]
+
+trait Foo {
+    const fn bar() -> u32; // error!
+}
+```
+
 Trait methods cannot be declared `const` by design. For more information, see
 [RFC 911].
 
diff --git a/src/librustc_expand/mbe/transcribe.rs b/src/librustc_expand/mbe/transcribe.rs
index 80bf02b1366e0..d12dedf9e0c7a 100644
--- a/src/librustc_expand/mbe/transcribe.rs
+++ b/src/librustc_expand/mbe/transcribe.rs
@@ -119,9 +119,9 @@ pub(super) fn transcribe(
         let tree = if let Some(tree) = stack.last_mut().unwrap().next() {
             // If it still has a TokenTree we have not looked at yet, use that tree.
             tree
-        }
-        // The else-case never produces a value for `tree` (it `continue`s or `return`s).
-        else {
+        } else {
+            // This else-case never produces a value for `tree` (it `continue`s or `return`s).
+
             // Otherwise, if we have just reached the end of a sequence and we can keep repeating,
             // go back to the beginning of the sequence.
             if let Frame::Sequence { idx, sep, .. } = stack.last_mut().unwrap() {
diff --git a/src/librustc_incremental/persist/work_product.rs b/src/librustc_incremental/persist/work_product.rs
index 65a742a202ddd..b1861acec0426 100644
--- a/src/librustc_incremental/persist/work_product.rs
+++ b/src/librustc_incremental/persist/work_product.rs
@@ -13,9 +13,7 @@ pub fn copy_cgu_workproducts_to_incr_comp_cache_dir(
     files: &[(WorkProductFileKind, PathBuf)],
 ) -> Option<(WorkProductId, WorkProduct)> {
     debug!("copy_cgu_workproducts_to_incr_comp_cache_dir({:?},{:?})", cgu_name, files);
-    if sess.opts.incremental.is_none() {
-        return None;
-    }
+    sess.opts.incremental.as_ref()?;
 
     let saved_files = files
         .iter()
diff --git a/src/librustc_infer/traits/error_reporting/suggestions.rs b/src/librustc_infer/traits/error_reporting/suggestions.rs
index ed6cfa51cdf18..d05955fb858c0 100644
--- a/src/librustc_infer/traits/error_reporting/suggestions.rs
+++ b/src/librustc_infer/traits/error_reporting/suggestions.rs
@@ -401,9 +401,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
             let refs_number =
                 snippet.chars().filter(|c| !c.is_whitespace()).take_while(|c| *c == '&').count();
-            if let Some('\'') =
-                snippet.chars().filter(|c| !c.is_whitespace()).skip(refs_number).next()
-            {
+            if let Some('\'') = snippet.chars().filter(|c| !c.is_whitespace()).nth(refs_number) {
                 // Do not suggest removal of borrow from type arguments.
                 return;
             }
@@ -464,9 +462,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
             let refs_number =
                 snippet.chars().filter(|c| !c.is_whitespace()).take_while(|c| *c == '&').count();
-            if let Some('\'') =
-                snippet.chars().filter(|c| !c.is_whitespace()).skip(refs_number).next()
-            {
+            if let Some('\'') = snippet.chars().filter(|c| !c.is_whitespace()).nth(refs_number) {
                 // Do not suggest removal of borrow from type arguments.
                 return;
             }
diff --git a/src/librustc_mir/interpret/cast.rs b/src/librustc_mir/interpret/cast.rs
index 1a0be582ce67f..3cbb0667ff392 100644
--- a/src/librustc_mir/interpret/cast.rs
+++ b/src/librustc_mir/interpret/cast.rs
@@ -202,7 +202,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
             Char => {
                 // `u8` to `char` cast
-                debug_assert_eq!(v as u8 as u128, v);
+                assert_eq!(v as u8 as u128, v);
                 Ok(Scalar::from_uint(v, Size::from_bytes(4)))
             }
 
diff --git a/src/librustc_mir/interpret/operator.rs b/src/librustc_mir/interpret/operator.rs
index cd7a419af9508..f2ee5e047a88e 100644
--- a/src/librustc_mir/interpret/operator.rs
+++ b/src/librustc_mir/interpret/operator.rs
@@ -234,7 +234,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty),
 
             Add | Sub | Mul | Rem | Div => {
-                debug_assert!(!left_layout.abi.is_signed());
+                assert!(!left_layout.abi.is_signed());
                 let op: fn(u128, u128) -> (u128, bool) = match bin_op {
                     Add => u128::overflowing_add,
                     Sub => u128::overflowing_sub,
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index 7d59c0181a8f3..f298a6677d6dc 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -287,7 +287,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         self.eval_terminator(terminator)?;
         if !self.stack.is_empty() {
             // This should change *something*
-            debug_assert!(self.cur_frame() != old_stack || self.frame().block != old_bb);
+            assert!(self.cur_frame() != old_stack || self.frame().block != old_bb);
             if let Some(block) = self.frame().block {
                 info!("// executing {:?}", block);
             }
diff --git a/src/librustc_mir/interpret/terminator.rs b/src/librustc_mir/interpret/terminator.rs
index 53e10f86a2cec..08d4ae34afbfa 100644
--- a/src/librustc_mir/interpret/terminator.rs
+++ b/src/librustc_mir/interpret/terminator.rs
@@ -172,7 +172,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
         let caller_arg = caller_arg.next().ok_or_else(|| err_unsup!(FunctionArgCountMismatch))?;
         if rust_abi {
-            debug_assert!(!caller_arg.layout.is_zst(), "ZSTs must have been already filtered out");
+            assert!(!caller_arg.layout.is_zst(), "ZSTs must have been already filtered out");
         }
         // Now, check
         if !Self::check_argument_compat(rust_abi, caller_arg.layout, callee_arg.layout) {
diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 263883d56399a..50ba3e938957a 100644
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -144,16 +144,16 @@ fn wrapping_range_contains(r: &RangeInclusive<u128>, test: u128) -> bool {
 // "expected something <in the given range>" makes sense.
 fn wrapping_range_format(r: &RangeInclusive<u128>, max_hi: u128) -> String {
     let (lo, hi) = r.clone().into_inner();
-    debug_assert!(hi <= max_hi);
+    assert!(hi <= max_hi);
     if lo > hi {
         format!("less or equal to {}, or greater or equal to {}", hi, lo)
     } else if lo == hi {
         format!("equal to {}", lo)
     } else if lo == 0 {
-        debug_assert!(hi < max_hi, "should not be printing if the range covers everything");
+        assert!(hi < max_hi, "should not be printing if the range covers everything");
         format!("less or equal to {}", hi)
     } else if hi == max_hi {
-        debug_assert!(lo > 0, "should not be printing if the range covers everything");
+        assert!(lo > 0, "should not be printing if the range covers everything");
         format!("greater or equal to {}", lo)
     } else {
         format!("in the range {:?}", r)
diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
index f6a93363dc109..862a7ef1e73c0 100644
--- a/src/librustc_mir/monomorphize/collector.rs
+++ b/src/librustc_mir/monomorphize/collector.rs
@@ -824,11 +824,8 @@ fn find_vtable_types_for_unsizing<'tcx>(
         (&ty::Adt(source_adt_def, source_substs), &ty::Adt(target_adt_def, target_substs)) => {
             assert_eq!(source_adt_def, target_adt_def);
 
-            let kind = monomorphize::custom_coerce_unsize_info(tcx, source_ty, target_ty);
-
-            let coerce_index = match kind {
-                CustomCoerceUnsized::Struct(i) => i,
-            };
+            let CustomCoerceUnsized::Struct(coerce_index) =
+                monomorphize::custom_coerce_unsize_info(tcx, source_ty, target_ty);
 
             let source_fields = &source_adt_def.non_enum_variant().fields;
             let target_fields = &target_adt_def.non_enum_variant().fields;
diff --git a/src/librustc_span/source_map.rs b/src/librustc_span/source_map.rs
index 39601ad76222c..e0bbaf730a537 100644
--- a/src/librustc_span/source_map.rs
+++ b/src/librustc_span/source_map.rs
@@ -689,7 +689,7 @@ impl SourceMap {
                 whitespace_found = true;
             }
 
-            if whitespace_found && !c.is_whitespace() { false } else { true }
+            !whitespace_found || c.is_whitespace()
         })
     }
 
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs
index 14f7a6b6817ef..3a2a315a1027d 100644
--- a/src/librustc_typeck/check/demand.rs
+++ b/src/librustc_typeck/check/demand.rs
@@ -236,8 +236,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     //
                     // FIXME? Other potential candidate methods: `as_ref` and
                     // `as_mut`?
-                    .find(|a| a.check_name(sym::rustc_conversion_suggestion))
-                    .is_some()
+                    .any(|a| a.check_name(sym::rustc_conversion_suggestion))
         });
 
         methods
diff --git a/src/librustc_typeck/coherence/inherent_impls_overlap.rs b/src/librustc_typeck/coherence/inherent_impls_overlap.rs
index fcded27463e92..778eee3586b4b 100644
--- a/src/librustc_typeck/coherence/inherent_impls_overlap.rs
+++ b/src/librustc_typeck/coherence/inherent_impls_overlap.rs
@@ -23,14 +23,11 @@ impl InherentOverlapChecker<'tcx> {
         let impl_items2 = self.tcx.associated_items(impl2);
 
         for item1 in impl_items1.in_definition_order() {
-            let collision = impl_items2
-                .filter_by_name_unhygienic(item1.ident.name)
-                .find(|item2| {
-                    // Symbols and namespace match, compare hygienically.
-                    item1.kind.namespace() == item2.kind.namespace()
-                        && item1.ident.modern() == item2.ident.modern()
-                })
-                .is_some();
+            let collision = impl_items2.filter_by_name_unhygienic(item1.ident.name).any(|item2| {
+                // Symbols and namespace match, compare hygienically.
+                item1.kind.namespace() == item2.kind.namespace()
+                    && item1.ident.modern() == item2.ident.modern()
+            });
 
             if collision {
                 return true;
diff --git a/src/rustllvm/PassWrapper.cpp b/src/rustllvm/PassWrapper.cpp
index 65071c3ed86e0..90d24d20737db 100644
--- a/src/rustllvm/PassWrapper.cpp
+++ b/src/rustllvm/PassWrapper.cpp
@@ -868,8 +868,10 @@ LLVMRustOptimizeWithNewPassManager(
     } else {
       for (const auto &C : PipelineStartEPCallbacks)
         PB.registerPipelineStartEPCallback(C);
-      for (const auto &C : OptimizerLastEPCallbacks)
-        PB.registerOptimizerLastEPCallback(C);
+      if (OptStage != LLVMRustOptStage::PreLinkThinLTO) {
+        for (const auto &C : OptimizerLastEPCallbacks)
+          PB.registerOptimizerLastEPCallback(C);
+      }
 
       switch (OptStage) {
       case LLVMRustOptStage::PreLinkNoLTO:
@@ -877,6 +879,12 @@ LLVMRustOptimizeWithNewPassManager(
         break;
       case LLVMRustOptStage::PreLinkThinLTO:
         MPM = PB.buildThinLTOPreLinkDefaultPipeline(OptLevel, DebugPassManager);
+        if (!OptimizerLastEPCallbacks.empty()) {
+          FunctionPassManager FPM(DebugPassManager);
+          for (const auto &C : OptimizerLastEPCallbacks)
+            C(FPM, OptLevel);
+          MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
+        }
         break;
       case LLVMRustOptStage::PreLinkFatLTO:
         MPM = PB.buildLTOPreLinkDefaultPipeline(OptLevel, DebugPassManager);
diff --git a/src/test/codegen/sanitizer-recover.rs b/src/test/codegen/sanitizer-recover.rs
index 9a583725b0bf0..05b4ab5653cc8 100644
--- a/src/test/codegen/sanitizer-recover.rs
+++ b/src/test/codegen/sanitizer-recover.rs
@@ -14,8 +14,8 @@
 //[MSAN-RECOVER-LTO] compile-flags: -Zsanitizer=memory  -Zsanitizer-recover=memory -C lto=fat
 //
 // MSAN-NOT:         @__msan_keep_going
-// MSAN-RECOVER:     @__msan_keep_going = weak_odr {{.*}} constant i32 1
-// MSAN-RECOVER-LTO: @__msan_keep_going = weak_odr {{.*}} constant i32 1
+// MSAN-RECOVER:     @__msan_keep_going = weak_odr {{.*}}constant i32 1
+// MSAN-RECOVER-LTO: @__msan_keep_going = weak_odr {{.*}}constant i32 1
 
 // ASAN-LABEL: define i32 @penguin(
 // ASAN:         call void @__asan_report_load4(i64 %0)
diff --git a/src/test/ui/sanitize/new-llvm-pass-manager-thin-lto.rs b/src/test/ui/sanitize/new-llvm-pass-manager-thin-lto.rs
new file mode 100644
index 0000000000000..61d5d51cfd248
--- /dev/null
+++ b/src/test/ui/sanitize/new-llvm-pass-manager-thin-lto.rs
@@ -0,0 +1,27 @@
+// Regression test for sanitizer function instrumentation passes not
+// being run when compiling with new LLVM pass manager and ThinLTO.
+// Note: The issue occured only on non-zero opt-level.
+//
+// min-llvm-version 9.0
+// needs-sanitizer-support
+// only-x86_64
+//
+// no-prefer-dynamic
+// revisions: opt0 opt1
+// compile-flags: -Znew-llvm-pass-manager=yes -Zsanitizer=address -Clto=thin
+//[opt0]compile-flags: -Copt-level=0
+//[opt1]compile-flags: -Copt-level=1
+// run-fail
+// error-pattern: ERROR: AddressSanitizer: stack-use-after-scope
+
+static mut P: *mut usize = std::ptr::null_mut();
+
+fn main() {
+    unsafe {
+        {
+            let mut x = 0;
+            P = &mut x;
+        }
+        std::ptr::write_volatile(P, 123);
+    }
+}
diff --git a/src/tools/compiletest/src/header/tests.rs b/src/tools/compiletest/src/header/tests.rs
index 38fa778219de2..6c478f7e29da4 100644
--- a/src/tools/compiletest/src/header/tests.rs
+++ b/src/tools/compiletest/src/header/tests.rs
@@ -109,6 +109,24 @@ fn no_system_llvm() {
     assert!(parse_rs(&config, "// no-system-llvm").ignore);
 }
 
+#[test]
+fn llvm_version() {
+    let mut config = config();
+
+    config.llvm_version = Some("8.1.2-rust".to_owned());
+    assert!(parse_rs(&config, "// min-llvm-version 9.0").ignore);
+
+    config.llvm_version = Some("9.0.1-rust-1.43.0-dev".to_owned());
+    assert!(parse_rs(&config, "// min-llvm-version 9.2").ignore);
+
+    config.llvm_version = Some("9.3.1-rust-1.43.0-dev".to_owned());
+    assert!(!parse_rs(&config, "// min-llvm-version 9.2").ignore);
+
+    // FIXME.
+    // config.llvm_version = Some("10.0.0-rust".to_owned());
+    // assert!(!parse_rs(&config, "// min-llvm-version 9.0").ignore);
+}
+
 #[test]
 fn ignore_target() {
     let mut config = config();