From 87a09b2ad577fb6f9725dbc2e1adc5e75f783638 Mon Sep 17 00:00:00 2001
From: Daniel Paoliello <danpao@microsoft.com>
Date: Fri, 8 Aug 2025 12:21:57 -0700
Subject: [PATCH] [win][arm64ec] Add '/machine:arm64ec' when linking LLVM as
 Arm64EC

---
 src/bootstrap/src/core/build_steps/llvm.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/bootstrap/src/core/build_steps/llvm.rs b/src/bootstrap/src/core/build_steps/llvm.rs
index 721ba6ca459e4..79772330a6d98 100644
--- a/src/bootstrap/src/core/build_steps/llvm.rs
+++ b/src/bootstrap/src/core/build_steps/llvm.rs
@@ -421,6 +421,13 @@ impl Step for Llvm {
             ldflags.shared.push(" -latomic");
         }
 
+        if target.starts_with("arm64ec") {
+            // MSVC linker requires the -machine:arm64ec flag to be passed to
+            // know it's linking as Arm64EC (vs Arm64X).
+            ldflags.exe.push(" -machine:arm64ec");
+            ldflags.shared.push(" -machine:arm64ec");
+        }
+
         if target.is_msvc() {
             cfg.define("CMAKE_MSVC_RUNTIME_LIBRARY", "MultiThreaded");
             cfg.static_crt(true);