From 2323410146038e3a876ad9fa59509fff13d20d2a Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sun, 23 Nov 2025 17:15:29 +0200
Subject: [PATCH] improve handling of noreturn statements

---
 src/Translator.zig                        | 32 ++++-------
 src/ast.zig                               | 19 ++++---
 test/cases/translate/bool_not.c           | 12 ++--
 test/cases/translate/continue_in_switch.c | 67 +++++++++++++++++++++++
 test/cases/translate/do_loop.c            | 12 ++++
 test/cases/translate/early_return.c       | 10 ++++
 test/cases/translate/switch_on_int.c      |  4 +-
 7 files changed, 119 insertions(+), 37 deletions(-)
 create mode 100644 test/cases/translate/continue_in_switch.c
 create mode 100644 test/cases/translate/early_return.c

diff --git a/src/Translator.zig b/src/Translator.zig
index 01248b9..80ddd5c 100644
--- a/src/Translator.zig
+++ b/src/Translator.zig
@@ -1618,7 +1618,10 @@ fn transCompoundStmtInline(t: *Translator, compound: Node.CompoundStmt, block: *
         const result = try t.transStmt(&block.base, stmt);
         switch (result.tag()) {
             .declaration, .empty_block => {},
-            else => try block.statements.append(t.gpa, result),
+            else => {
+                try block.statements.append(t.gpa, result);
+                if (result.isNoreturn()) return;
+            },
         }
     }
 }
@@ -1754,7 +1757,7 @@ fn transDoWhileStmt(t: *Translator, scope: *Scope, do_stmt: Node.DoWhileStmt) Tr
     };
 
     var body_node = try t.transStmt(&loop_scope, do_stmt.body);
-    if (body_node.isNoreturn(true)) {
+    if (body_node.isNoreturn()) {
         // The body node ends in a noreturn statement. Simply put it in a while (true)
         // in case it contains breaks or continues.
     } else if (do_stmt.body.get(t.tree) == .compound_stmt) {
@@ -1974,8 +1977,6 @@ fn transSwitchProngStmt(
     body: []const Node.Index,
 ) TransError!ZigNode {
     switch (stmt.get(t.tree)) {
-        .break_stmt => return ZigTag.@"break".init(),
-        .return_stmt => return t.transStmt(scope, stmt),
         .case_stmt, .default_stmt => unreachable,
         else => {
             var block_scope = try Scope.Block.init(t, scope, false);
@@ -1996,15 +1997,6 @@ fn transSwitchProngStmtInline(
 ) TransError!void {
     for (body) |stmt| {
         switch (stmt.get(t.tree)) {
-            .return_stmt => {
-                const result = try t.transStmt(&block.base, stmt);
-                try block.statements.append(t.gpa, result);
-                return;
-            },
-            .break_stmt => {
-                try block.statements.append(t.gpa, ZigTag.@"break".init());
-                return;
-            },
             .case_stmt => |case_stmt| {
                 var sub = case_stmt.body;
                 while (true) switch (sub.get(t.tree)) {
@@ -2015,7 +2007,7 @@ fn transSwitchProngStmtInline(
                 const result = try t.transStmt(&block.base, sub);
                 assert(result.tag() != .declaration);
                 try block.statements.append(t.gpa, result);
-                if (result.isNoreturn(true)) return;
+                if (result.isNoreturn()) return;
             },
             .default_stmt => |default_stmt| {
                 var sub = default_stmt.body;
@@ -2027,18 +2019,16 @@ fn transSwitchProngStmtInline(
                 const result = try t.transStmt(&block.base, sub);
                 assert(result.tag() != .declaration);
                 try block.statements.append(t.gpa, result);
-                if (result.isNoreturn(true)) return;
-            },
-            .compound_stmt => |compound_stmt| {
-                const result = try t.transCompoundStmt(&block.base, compound_stmt);
-                try block.statements.append(t.gpa, result);
-                if (result.isNoreturn(true)) return;
+                if (result.isNoreturn()) return;
             },
             else => {
                 const result = try t.transStmt(&block.base, stmt);
                 switch (result.tag()) {
                     .declaration, .empty_block => {},
-                    else => try block.statements.append(t.gpa, result),
+                    else => {
+                        try block.statements.append(t.gpa, result);
+                        if (result.isNoreturn()) return;
+                    },
                 }
             },
         }
diff --git a/src/ast.zig b/src/ast.zig
index b7a8fd4..47ad1d6 100644
--- a/src/ast.zig
+++ b/src/ast.zig
@@ -455,14 +455,14 @@ pub const Node = extern union {
         return .{ .ptr_otherwise = payload };
     }
 
-    pub fn isNoreturn(node: Node, break_counts: bool) bool {
-        switch (node.tag()) {
+    pub fn isNoreturn(node: Node) bool {
+        return switch (node.tag()) {
             .block => {
                 const block_node = node.castTag(.block).?;
                 if (block_node.data.stmts.len == 0) return false;
 
                 const last = block_node.data.stmts[block_node.data.stmts.len - 1];
-                return last.isNoreturn(break_counts);
+                return last.isNoreturn();
             },
             .@"switch" => {
                 const switch_node = node.castTag(.@"switch").?;
@@ -475,15 +475,16 @@ pub const Node = extern union {
                     else
                         unreachable;
 
-                    if (!body.isNoreturn(break_counts)) return false;
+                    if (!body.isNoreturn()) return false;
                 }
                 return true;
             },
-            .@"return", .return_void => return true,
-            .@"break" => if (break_counts) return true,
-            else => {},
-        }
-        return false;
+            .@"return", .return_void => true,
+            .@"break" => true,
+            .@"continue" => true,
+            .@"unreachable" => true,
+            else => false,
+        };
     }
 
     pub fn isBoolRes(res: Node) bool {
diff --git a/test/cases/translate/bool_not.c b/test/cases/translate/bool_not.c
index b2bd564..bf0b2f4 100644
--- a/test/cases/translate/bool_not.c
+++ b/test/cases/translate/bool_not.c
@@ -2,9 +2,9 @@ int foo() {
     int a;
     float b;
     void *c;
-    return !(a == 0);
-    return !a;
-    return !b;
+    if (1) return !(a == 0);
+    if (1) return !a;
+    if (1) return !b;
     return !c;
 }
 
@@ -17,8 +17,8 @@ int foo() {
 //     _ = &b;
 //     var c: ?*anyopaque = undefined;
 //     _ = &c;
-//     return @intFromBool(!(a == @as(c_int, 0)));
-//     return @intFromBool(!(a != 0));
-//     return @intFromBool(!(b != 0));
+//     if (true) return @intFromBool(!(a == @as(c_int, 0)));
+//     if (true) return @intFromBool(!(a != 0));
+//     if (true) return @intFromBool(!(b != 0));
 //     return @intFromBool(!(c != null));
 // }
diff --git a/test/cases/translate/continue_in_switch.c b/test/cases/translate/continue_in_switch.c
new file mode 100644
index 0000000..766b5d1
--- /dev/null
+++ b/test/cases/translate/continue_in_switch.c
@@ -0,0 +1,67 @@
+int entry(int i) {
+    int res = i;
+    while (1) switch (res) {
+        case 0:
+            res += 1;
+        case 1:
+            continue;
+        case 2: {
+            continue;
+        }
+        case 3:
+            if (res == 42) return - 1;
+            res = 42;
+            continue;
+        case 4:
+            return 1;
+        case 5:
+            res = 10;
+        default:
+            break;
+    };
+    return res;
+}
+
+// translate
+//
+// pub export fn entry(arg_i: c_int) c_int {
+//     var i = arg_i;
+//     _ = &i;
+//     var res: c_int = i;
+//     _ = &res;
+//     while (true) {
+//         while (true) {
+//             switch (res) {
+//                 @as(c_int, 0) => {
+//                     res += 1;
+//                     continue;
+//                 },
+//                 @as(c_int, 1) => {
+//                     continue;
+//                 },
+//                 @as(c_int, 2) => {
+//                     {
+//                         continue;
+//                     }
+//                 },
+//                 @as(c_int, 3) => {
+//                     if (res == @as(c_int, 42)) return -@as(c_int, 1);
+//                     res = 42;
+//                     continue;
+//                 },
+//                 @as(c_int, 4) => {
+//                     return 1;
+//                 },
+//                 @as(c_int, 5) => {
+//                     res = 10;
+//                     break;
+//                 },
+//                 else => {
+//                     break;
+//                 },
+//             }
+//             break;
+//         }
+//     }
+//     return res;
+// }
diff --git a/test/cases/translate/do_loop.c b/test/cases/translate/do_loop.c
index e8cddac..80a132f 100644
--- a/test/cases/translate/do_loop.c
+++ b/test/cases/translate/do_loop.c
@@ -8,6 +8,12 @@ void foo(void) {
     do
         b = b -1;
     while (b);
+    do {
+        __builtin_unreachable();
+    } while (0);
+    do {
+        continue;
+    } while (1);
 }
 
 // translate
@@ -25,4 +31,10 @@ void foo(void) {
 //         b = b - @as(c_int, 1);
 //         if (!(b != 0)) break;
 //     }
+//     while (true) {
+//         unreachable;
+//     }
+//     while (true) {
+//         continue;
+//     }
 // }
diff --git a/test/cases/translate/early_return.c b/test/cases/translate/early_return.c
new file mode 100644
index 0000000..00d30fe
--- /dev/null
+++ b/test/cases/translate/early_return.c
@@ -0,0 +1,10 @@
+static unsigned long early_return(void) {
+	return 8 * 1024 * 1024;
+	return 2 * 1024 * 1024;
+}
+
+// translate
+//
+// pub fn early_return() callconv(.c) c_ulong {
+//     return @bitCast(@as(c_long, (@as(c_int, 8) * @as(c_int, 1024)) * @as(c_int, 1024)));
+// }
diff --git a/test/cases/translate/switch_on_int.c b/test/cases/translate/switch_on_int.c
index ac61d39..58f5a3a 100644
--- a/test/cases/translate/switch_on_int.c
+++ b/test/cases/translate/switch_on_int.c
@@ -69,7 +69,9 @@ void switch_fn(int i) {
 //             @as(c_int, 6) => {
 //                 while (true) {
 //                     switch (res) {
-//                         @as(c_int, 9) => break,
+//                         @as(c_int, 9) => {
+//                             break;
+//                         },
 //                         else => {},
 //                     }
 //                     break;