1 files changed, 7 insertions, 22 deletions

diff --git a/src/compile.zig b/src/compile.zig
index c837495..ac7768e 100644
--- a/src/compile.zig
+++ b/src/compile.zig
@@ -15,7 +15,6 @@ pub const Instr = struct {
         constant: Constant,
         bin_op: BinOp,
         proc_call: ProcCall,
-        discard: Discard,
     };
 
     pub const Constant = struct {
@@ -58,14 +57,6 @@ pub const Instr = struct {
         }
     };
 
-    pub const Discard = struct {
-        vreg: VReg,
-
-        pub fn sources(self: Discard) Sources {
-            return Sources.fromSlice(&.{self.vreg}) catch unreachable;
-        }
-    };
-
     pub fn sources(self: Instr) Sources {
         return switch (self.type) {
             inline else => |instr| instr.sources(),
@@ -75,7 +66,6 @@ pub const Instr = struct {
     pub fn dest(self: *const Instr) ?VReg {
         return switch (self.type) {
             inline .constant, .bin_op, .proc_call => |s| s.dest,
-            // inline .x => null,
         };
     }
 
@@ -85,17 +75,15 @@ pub const Instr = struct {
 pub const Block = struct {
     // arguments: []Reg,
     instrs: []Instr,
-    vreg_last_use: std.AutoHashMap(usize, std.ArrayList(VReg)),
+    vreg_last_use: std.AutoHashMap(VReg, usize),
 
     fn init(allocator: Allocator, instrs: []Instr) !Block {
-        var vreg_last_use: std.AutoHashMap(usize, std.ArrayList(VReg)) = .init(allocator);
+        var vreg_last_use: std.AutoHashMap(VReg, usize) = .init(allocator);
         for (0.., instrs) |i, instr| {
-            const kv = try vreg_last_use.getOrPut(i);
-            if (!kv.found_existing) kv.value_ptr.* = .init(allocator);
-            for (instr.sources().slice()) |src| {
-                if (std.mem.indexOfScalar(VReg, kv.value_ptr.items, src) == null)
-                    try kv.value_ptr.append(src);
-            }
+            for (instr.sources().slice()) |src|
+                try vreg_last_use.put(src, i);
+            if (instr.dest()) |dest|
+                try vreg_last_use.put(dest, i);
         }
         return .{
             .instrs = instrs,
@@ -134,10 +122,7 @@ const CompileContext = struct {
 
     fn compileStmt(self: *Self, stmt: parse.Stmt) !void {
         switch (stmt.type) {
-            .expr => |expr| try self.addInstr(.{
-                .loc = stmt.loc,
-                .type = .{ .discard = .{ .vreg = try self.compileExpr(expr) } },
-            }),
+            .expr => |expr| _ = try self.compileExpr(expr),
             .declare_var => |declare_var| {
                 const val = try self.compileExpr(declare_var.value);
                 const name = declare_var.ident.getIdent(self.source);