From f448b518f874929dd219ed957c314889d5dbf0cf Mon Sep 17 00:00:00 2001
From: Noam Preil <noam@pixelhero.dev>
Date: Fri, 21 Aug 2020 18:19:23 -0400
Subject: [PATCH] SPU-II: use undefined1 as breakpoint

---
 lib/std/spu/interpreter.zig | 9 ++++++++-
 src-self-hosted/codegen.zig | 6 +++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/std/spu/interpreter.zig b/lib/std/spu/interpreter.zig
index 66d75a5676..d008955a93 100644
--- a/lib/std/spu/interpreter.zig
+++ b/lib/std/spu/interpreter.zig
@@ -11,6 +11,9 @@ pub fn Interpreter(comptime Bus: type) type {
         /// This is set to true when we hit an undefined0 instruction, allowing it to
         /// be used as a trap for testing purposes
         undefined0: bool = false,
+        /// This is set to true when we hit an undefined1 instruction, allowing it to
+        /// be used as a trap for testing purposes. undefined1 is used as a breakpoint.
+        undefined1: bool = false,
         bus: Bus,
 
         pub fn ExecuteBlock(self: *@This(), comptime size: ?u32) !void {
@@ -122,7 +125,11 @@ pub fn Interpreter(comptime Bus: type) type {
                             // Break out of the loop, and let the caller decide what to do
                             return;
                         },
-                        .undefined1 => return error.BadInstruction,
+                        .undefined1 => {
+                            self.undefined1 = true;
+                            // Break out of the loop, and let the caller decide what to do
+                            return;
+                        },
                         .signext => if ((val0 & 0x80) != 0)
                             (val0 & 0xFF) | 0xFF00
                         else
diff --git a/src-self-hosted/codegen.zig b/src-self-hosted/codegen.zig
index aec4ea81e6..c3cb1fb8e2 100644
--- a/src-self-hosted/codegen.zig
+++ b/src-self-hosted/codegen.zig
@@ -1265,7 +1265,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                 .riscv64 => {
                     mem.writeIntLittle(u32, try self.code.addManyAsArray(4), Instruction.ebreak.toU32());
                 },
-                .spu_2 => {},
+                .spu_2 => {
+                    try self.code.resize(self.code.items.len + 2);
+                    var instr = Instruction{ .condition = .always, .input0 = .zero, .input1 = .zero, .modify_flags = false, .output = .discard, .command = .undefined1 };
+                    mem.writeIntLittle(u16, self.code.items[self.code.items.len - 2 ..][0..2], @bitCast(u16, instr));
+                },
                 else => return self.fail(src, "TODO implement @breakpoint() for {}", .{self.target.cpu.arch}),
             }
             return .none;