Add console tetris demo

apps/zigtris/src/uvm.zig

@@ -0,0 +1,73 @@
+const uvm32 = @cImport({
+    @cDefine("USE_MAIN", "1");
+    @cInclude("uvm32_target.h");
+});
+const std = @import("std");
+
+// dupeZ would be better, but want to avoid using an allocator
+var new_buf:[128]u8 = undefined;
+pub inline fn print(m: []const u8) void {
+    @memcpy(new_buf[0..m.len], m);
+    new_buf[m.len] = 0;
+    const s = new_buf[0..m.len :0];
+
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_PRINT}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (s.ptr),
+    );
+}
+
+pub inline fn println(val: [:0]const u8) void {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_PRINTLN}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (val.ptr),
+    );
+}
+
+pub inline fn printd(val: u32) void {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_PRINTD}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (val),
+    );
+}
+
+pub inline fn printx(val: u32) void {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_PRINTX}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (val),
+    );
+}
+
+pub inline fn printc(val: u32) void {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_PRINTC}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (val),
+    );
+}
+
+pub inline fn yield() void {
+    asm volatile (std.fmt.comptimePrint("csrwi 0x{x}, 0", .{uvm32.IOREQ_YIELD}));
+}
+
+var millis_storage:u32 = 0;
+pub inline fn millis() u32 {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_MILLIS}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (&millis_storage),
+    );
+    return millis_storage;
+}
+
+var getch_storage:u32 = 0;
+pub inline fn getch() ?u8 {
+    asm volatile ("csrw " ++ std.fmt.comptimePrint("0x{x}", .{uvm32.IOREQ_GETC}) ++ ", %[arg1]"
+        :
+        : [arg1] "r" (&getch_storage),
+    );
+    if (getch_storage <= 0xFF) {
+        return @truncate(getch_storage);
+    } else {
+        return null;
+    }
+}
+