# What: provide and link MinGW's ARM64 long-double `powl` compatibility shim.
# Why: Windows ARM64 uses 64-bit long doubles, but LLVM's Bazel source list
# omits the upstream `powl -> pow` implementation and its default link flags
# omit the MinGW extension archive that owns the shim.

diff --git a/runtimes/mingw/crt_sources.bzl b/runtimes/mingw/crt_sources.bzl
--- a/runtimes/mingw/crt_sources.bzl
+++ b/runtimes/mingw/crt_sources.bzl
@@ -420,4 +420,5 @@
 MINGWEX_ARM64_SRCS = [
+    "math/arm-common/powl.c",
     "math/sincos.c",
     "math/sincosf.c",
     "math/arm-common/sincosl.c",
diff --git a/toolchain/args/windows/BUILD.bazel b/toolchain/args/windows/BUILD.bazel
--- a/toolchain/args/windows/BUILD.bazel
+++ b/toolchain/args/windows/BUILD.bazel
@@ -49,5 +49,6 @@ cc_args(
+        "-lmingwex",
         # For now, we force on ucrt.
         # TODO(cerisier): make this either a constraint or a build setting
         "-lucrt",
     ],
     data = [