Prepare for supporting cross compilation.

PiperOrigin-RevId: 346496532

1 files changed, 41 insertions, 0 deletions

diff --git a/tools/bazeldefs/defs.bzl b/tools/bazeldefs/defs.bzl
index 51e17a79a..279a38fed 100644
--- a/tools/bazeldefs/defs.bzl
+++ b/tools/bazeldefs/defs.bzl
@@ -39,3 +39,44 @@ def default_net_util():
 
 def coreutil():
     return []  # Nothing needed.
+
+def select_native_vs_cross(native = [], amd64 = [], arm64 = [], cross = []):
+    values = {
+        "//tools/bazeldefs:linux_arm64_cross": arm64 + cross,
+        "//tools/bazeldefs:linux_amd64_cross": amd64 + cross,
+        "//conditions:default": native,
+    }
+    return select(values)
+
+def arch_genrule(name, srcs, outs, cmd, tools):
+    """Runs a gen command on the target architecture.
+
+    If the target architecture isn't match the host architecture, it will build
+    a command for the target architecture and run it via qemu.
+
+    The native genrule runs the command on the host architecture.
+
+    Args:
+     name: name of generated target.
+     srcs: A list of inputs for this rule.
+     cmd: The command to run. It has to contain " QEMU " before executed binaries.
+     outs: A list of files generated by this rule.
+     tools: A list of tool dependencies for this rule.
+    """
+    qemu_arm64 = "qemu-aarch64-static"
+    qemu_amd64 = "qemu-x86_64-static"
+    srcs = select_native_vs_cross(
+        cross = srcs + tools,
+        native = srcs,
+    )
+    tools = select_native_vs_cross(
+        cross = [],
+        native = tools,
+    )
+    cmd = select_native_vs_cross(
+        arm64 = cmd.replace("QEMU", qemu_arm64),
+        amd64 = cmd.replace("QEMU", qemu_amd64),
+        native = cmd.replace("QEMU", ""),
+        cross = "",
+    )
+    native.genrule(name = name, srcs = srcs, outs = outs, cmd = cmd, tools = tools)