From c6b902d2b7da0306ef5edda3658b9e055c6dcaae Mon Sep 17 00:00:00 2001
From: spaceface <spaceface7777@gmail.com>
Date: Thu, 16 Dec 2021 17:02:05 +0100
Subject: [PATCH] cgen: support closures on arm64 (#12863)

---
 cmd/tools/vtest-self.v  | 10 ++++++++--
 vlib/v/gen/c/cheaders.v | 29 ++++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/cmd/tools/vtest-self.v b/cmd/tools/vtest-self.v
index 3b387ae787..e3294344a7 100644
--- a/cmd/tools/vtest-self.v
+++ b/cmd/tools/vtest-self.v
@@ -130,7 +130,10 @@ const (
 	skip_on_amd64                 = [
 		'do_not_remove',
 	]
-	skip_on_non_amd64             = [
+	skip_on_arm64                 = [
+		'do_not_remove',
+	]
+	skip_on_non_amd64_or_arm64    = [
 		// closures aren't implemented yet:
 		'vlib/v/tests/closure_test.v',
 		'vlib/context/cancel_test.v',
@@ -232,12 +235,15 @@ fn main() {
 	if os.getenv('V_CI_UBUNTU_MUSL').len > 0 {
 		tsession.skip_files << skip_on_ubuntu_musl
 	}
-	$if !amd64 {
+	$if !amd64 && !arm64 {
 		tsession.skip_files << skip_on_non_amd64
 	}
 	$if amd64 {
 		tsession.skip_files << skip_on_amd64
 	}
+	$if arm64 {
+		tsession.skip_files << skip_on_arm64
+	}
 	$if !linux {
 		tsession.skip_files << skip_on_non_linux
 	}
diff --git a/vlib/v/gen/c/cheaders.v b/vlib/v/gen/c/cheaders.v
index 2bdb1df04e..fa8a226d1a 100644
--- a/vlib/v/gen/c/cheaders.v
+++ b/vlib/v/gen/c/cheaders.v
@@ -58,6 +58,15 @@ static inline void __sort_ptr(uintptr_t a[], bool b[], int l) {
 }
 '
 
+fn arm_bytes(nargs int) string {
+	// start:
+	// ldr  x16, start-0x08
+	// ldr  x<REG>, start-0x10
+	// br  x16
+	bytes := '0xd0, 0xff, 0xff, 0x58, 0x6<REG>, 0xff, 0xff, 0x58, 0x00, 0x02, 0x1f, 0xd6'
+	return bytes.replace('<REG>', nargs.str())
+}
+
 // Heavily based on Chris Wellons's work
 // https://nullprogram.com/blog/2017/01/08/
 
@@ -65,7 +74,7 @@ fn c_closure_helpers(pref &pref.Preferences) string {
 	if pref.os == .windows {
 		verror('closures are not implemented on Windows yet')
 	}
-	if pref.arch != .amd64 {
+	if pref.arch !in [.amd64, .arm64] {
 		verror('closures are not implemented on this architecture yet: $pref.arch')
 	}
 	mut builder := strings.new_builder(2048)
@@ -95,6 +104,24 @@ static unsigned char __closure_thunk[6][13] = {
         0xff, 0x25, 0xeb, 0xff, 0xff, 0xff
     },
 };
+')
+	} else if pref.arch == .arm64 {
+		builder.write_string('
+static unsigned char __closure_thunk[6][12] = {
+    {
+        ${arm_bytes(0)}
+    }, {
+        ${arm_bytes(1)}
+    }, {
+        ${arm_bytes(2)}
+    }, {
+        ${arm_bytes(3)}
+    }, {
+        ${arm_bytes(4)}
+    }, {
+        ${arm_bytes(5)}
+    },
+};
 ')
 	}
 	builder.write_string('