[win] Fix truncated unwinds for Arm64 Windows

dpaoliello · dpaoliello · commit 614bac581b9b · 2026-02-27T14:53:09.000-08:00
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -347,7 +347,13 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
     // option causes bugs in the LLVM WebAssembly backend. You should be able to
     // remove this check when Rust's minimum supported LLVM version is >= 18
     // https://github.com/llvm/llvm-project/pull/65876
-    if (!Trip.isWasm()) {
+    //
+    // Also keep traps after noreturn calls on Windows, because the trap is
+    // needed to keep the return address within the calling function's
+    // .pdata range. Without it, RtlLookupFunctionEntry resolves the wrong
+    // function and SEH unwinding (used for backtraces) terminates early.
+    // See https://github.com/rust-lang/rust/issues/140489
+    if (!Trip.isWasm() && !Trip.isOSWindows()) {
       Options.NoTrapAfterNoreturn = true;
     }
   }
diff --git a/tests/ui/runtime/backtrace-debuginfo.rs b/tests/ui/runtime/backtrace-debuginfo.rs
@@ -47,14 +47,9 @@ macro_rules! dump_and_die {
         // there, even on i686-pc-windows-msvc. We do the best we can in
         // rust-lang/rust to test it as well, but sometimes we just gotta keep
         // landing PRs.
-        //
-        // aarch64-msvc/arm64ec-msvc is broken as its backtraces are truncated.
-        // See https://github.com/rust-lang/rust/issues/140489
         if cfg!(any(target_os = "android",
                     all(target_os = "linux", target_arch = "arm"),
                     all(target_env = "msvc", target_arch = "x86"),
-                    all(target_env = "msvc", target_arch = "aarch64"),
-                    all(target_env = "msvc", target_arch = "arm64ec"),
                     target_os = "freebsd",
                     target_os = "dragonfly",
                     target_os = "openbsd")) {
