From 78fe86dcd23821b6a40bc5a0067513c452e50265 Mon Sep 17 00:00:00 2001
From: Noam Preil <noam@pixelhero.dev>
Date: Sun, 9 Aug 2020 18:52:32 -0400
Subject: [PATCH] CBE: support unreachable on GCC

---
 src-self-hosted/cbe.h         | 5 +++++
 src-self-hosted/codegen/c.zig | 2 +-
 test/stage2/cbe.zig           | 3 ++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src-self-hosted/cbe.h b/src-self-hosted/cbe.h
index 691aa45725..854032227d 100644
--- a/src-self-hosted/cbe.h
+++ b/src-self-hosted/cbe.h
@@ -8,3 +8,8 @@
 #define zig_noreturn
 #endif
 
+#if __GNUC__
+#define zig_unreachable() __builtin_unreachable()
+#else
+#define zig_unreachable()
+#endif
diff --git a/src-self-hosted/codegen/c.zig b/src-self-hosted/codegen/c.zig
index ba68a3a5a4..591e47967e 100644
--- a/src-self-hosted/codegen/c.zig
+++ b/src-self-hosted/codegen/c.zig
@@ -178,7 +178,7 @@ fn genBreak(file: *C, inst: *Inst.NoOp, decl: *Decl) !void {
 }
 
 fn genUnreach(file: *C, inst: *Inst.NoOp, decl: *Decl) !void {
-    // TODO ??
+    try file.main.writer().writeAll("    zig_unreachable();\n");
 }
 
 fn genAsm(file: *C, as: *Inst.Assembly, decl: *Decl, argdex: *usize) !void {
diff --git a/test/stage2/cbe.zig b/test/stage2/cbe.zig
index 36c4514d49..59bc062b74 100644
--- a/test/stage2/cbe.zig
+++ b/test/stage2/cbe.zig
@@ -65,7 +65,7 @@ pub fn addCases(ctx: *TestContext) !void {
         \\}
         \\
     );
-    ctx.c("exit", linux_x64,
+    ctx.c("exit with parameter", linux_x64,
         \\export fn _start() noreturn {
         \\    exit(0);
         \\}
@@ -96,6 +96,7 @@ pub fn addCases(ctx: *TestContext) !void {
         \\    register size_t rax_constant __asm__("rax") = 231;
         \\    register size_t rdi_constant __asm__("rdi") = arg0;
         \\    __asm volatile ("syscall" :: ""(rax_constant), ""(rdi_constant));
+        \\    zig_unreachable();
         \\}
         \\
     );