3 files changed, 12 insertions, 10 deletions
diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index 72961ae888e..fed56cdd438 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -15,7 +15,7 @@ pub(crate) unsafe fn codegen(
     module_llvm: &mut ModuleLlvm,
     module_name: &str,
     kind: AllocatorKind,
-    has_alloc_error_handler: bool,
+    alloc_error_handler_kind: AllocatorKind,
 ) {
     let llcx = &*module_llvm.llcx;
     let llmod = module_llvm.llmod();
@@ -117,8 +117,7 @@ pub(crate) unsafe fn codegen(
         attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
     }
 
-    let kind = if has_alloc_error_handler { AllocatorKind::Global } else { AllocatorKind::Default };
-    let callee = kind.fn_name(sym::oom);
+    let callee = alloc_error_handler_kind.fn_name(sym::oom);
     let callee = llvm::LLVMRustGetOrInsertFunction(llmod, callee.as_ptr().cast(), callee.len(), ty);
     // -> ! DIFlagNoReturn
     attributes::apply_to_llfn(callee, llvm::AttributePlace::Function, &[no_return]);
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index fca43a0d86d..9cb36ce7f18 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -365,11 +365,14 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 Int(I64) => "llvm.ssub.with.overflow.i64",
                 Int(I128) => "llvm.ssub.with.overflow.i128",
 
-                Uint(U8) => "llvm.usub.with.overflow.i8",
-                Uint(U16) => "llvm.usub.with.overflow.i16",
-                Uint(U32) => "llvm.usub.with.overflow.i32",
-                Uint(U64) => "llvm.usub.with.overflow.i64",
-                Uint(U128) => "llvm.usub.with.overflow.i128",
+                Uint(_) => {
+                    // Emit sub and icmp instead of llvm.usub.with.overflow. LLVM considers these
+                    // to be the canonical form. It will attempt to reform llvm.usub.with.overflow
+                    // in the backend if profitable.
+                    let sub = self.sub(lhs, rhs);
+                    let cmp = self.icmp(IntPredicate::IntULT, lhs, rhs);
+                    return (sub, cmp);
+                }
 
                 _ => unreachable!(),
             },
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 89c7e51d09e..d51aced85df 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -108,11 +108,11 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
         tcx: TyCtxt<'tcx>,
         module_name: &str,
         kind: AllocatorKind,
-        has_alloc_error_handler: bool,
+        alloc_error_handler_kind: AllocatorKind,
     ) -> ModuleLlvm {
         let mut module_llvm = ModuleLlvm::new_metadata(tcx, module_name);
         unsafe {
-            allocator::codegen(tcx, &mut module_llvm, module_name, kind, has_alloc_error_handler);
+            allocator::codegen(tcx, &mut module_llvm, module_name, kind, alloc_error_handler_kind);
         }
         module_llvm
     }