From 06d52f69408299eff611e57b39714b37abbb06a8 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Thu, 25 Nov 2021 09:42:29 -0800
Subject: Add __builtin_unreachable stub

---
 cc.h    | 1 +
 expr.c  | 4 ++++
 qbe.c   | 2 ++
 scope.c | 1 +
 4 files changed, 8 insertions(+)

diff --git a/cc.h b/cc.h
index 14b71b0..35a8fb8 100644
--- a/cc.h
+++ b/cc.h
@@ -250,6 +250,7 @@ enum builtinkind {
 	BUILTINNANF,
 	BUILTINOFFSETOF,
 	BUILTINTYPESCOMPATIBLEP,
+	BUILTINUNREACHABLE,
 	BUILTINVAARG,
 	BUILTINVACOPY,
 	BUILTINVAEND,
diff --git a/expr.c b/expr.c
index 6ff7dd4..5a8086a 100644
--- a/expr.c
+++ b/expr.c
@@ -756,6 +756,10 @@ builtinfunc(struct scope *s, enum builtinkind kind)
 		expect(TCOMMA, "after type name");
 		e = mkconstexpr(&typeint, typecompatible(t, typename(s, NULL)));
 		break;
+	case BUILTINUNREACHABLE:
+		e = mkexpr(EXPRBUILTIN, &typevoid, NULL);
+		e->builtin.kind = BUILTINUNREACHABLE;
+		break;
 	case BUILTINVAARG:
 		e = mkexpr(EXPRBUILTIN, NULL, assignexpr(s));
 		e->builtin.kind = BUILTINVAARG;
diff --git a/qbe.c b/qbe.c
index 264bdac..36fb0e4 100644
--- a/qbe.c
+++ b/qbe.c
@@ -954,6 +954,8 @@ funcexpr(struct func *f, struct expr *e)
 		case BUILTINALLOCA:
 			l = funcexpr(f, e->base);
 			return funcinst(f, IALLOC16, ptrclass, l, NULL);
+		case BUILTINUNREACHABLE:
+			return NULL;
 		default:
 			fatal("internal error: unimplemented builtin");
 		}
diff --git a/scope.c b/scope.c
index c116670..299d379 100644
--- a/scope.c
+++ b/scope.c
@@ -22,6 +22,7 @@ scopeinit(void)
 		{"__builtin_offsetof",   {.kind = DECLBUILTIN, .builtin = BUILTINOFFSETOF}},
 		{"__builtin_types_compatible_p",
 			{.kind = DECLBUILTIN, .builtin = BUILTINTYPESCOMPATIBLEP}},
+		{"__builtin_unreachable", {.kind = DECLBUILTIN, .builtin = BUILTINUNREACHABLE}},
 		{"__builtin_va_arg",     {.kind = DECLBUILTIN, .builtin = BUILTINVAARG}},
 		{"__builtin_va_copy",    {.kind = DECLBUILTIN, .builtin = BUILTINVACOPY}},
 		{"__builtin_va_end",     {.kind = DECLBUILTIN, .builtin = BUILTINVAEND}},
-- 
cgit v1.2.3