diff --git a/.gitmodules b/.gitmodules
index 0bbccb57130..e79f2f089c1 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -25,7 +25,7 @@
 [submodule "src/llvm-project"]
 	path = src/llvm-project
 	url = https://github.com/rust-lang/llvm-project.git
-	branch = rustc/16.0-2023-03-06
+	branch = rustc/15.0-2022-12-07
 [submodule "src/doc/embedded-book"]
 	path = src/doc/embedded-book
 	url = https://github.com/rust-embedded/book.git
diff --git a/src/llvm-project b/src/llvm-project
index 4bb5eab6ac3..fd949f3034f 160000
--- a/src/llvm-project
+++ b/src/llvm-project
@@ -1 +1 @@
-Subproject commit 4bb5eab6ac3faea4ab4e53c432a1643c3acec87e
+Subproject commit fd949f3034f8a422ecfffa889c2823485dde4bdd
diff --git a/tests/codegen/array-map.rs b/tests/codegen/array-map.rs
index 7b8ab2c79a7..9298e89e397 100644
--- a/tests/codegen/array-map.rs
+++ b/tests/codegen/array-map.rs
@@ -38,10 +38,10 @@
 //
 // CHECK-LABEL: @long_integer_map
 #[no_mangle]
-pub fn long_integer_map(x: [u32; 512]) -> [u32; 512] {
+pub fn long_integer_map(x: [u32; 64]) -> [u32; 64] {
     // CHECK: start:
-    // CHECK-NEXT: alloca [512 x i32]
-    // CHECK-NEXT: alloca %"core::mem::manually_drop::ManuallyDrop<[u32; 512]>"
+    // CHECK-NEXT: alloca [64 x i32]
+    // CHECK-NEXT: alloca %"core::mem::manually_drop::ManuallyDrop<[u32; 64]>"
     // CHECK-NOT: alloca
     // CHECK: mul <{{[0-9]+}} x i32>
     // CHECK: add <{{[0-9]+}} x i32>