From fed87e2006790fd3d0dbf41dc77ee4e4cc47fb16 Mon Sep 17 00:00:00 2001
From: Mathias Magnusson <mathias@magnusson.space>
Date: Sun, 1 Jun 2025 00:54:42 +0200
Subject: codegen: make register allocation fail with error rather than
 returning null

---
 src/codegen.zig | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/codegen.zig b/src/codegen.zig
index 368309c..0696d3a 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -398,7 +398,7 @@ const Instruction = packed union {
         imm20: u1,
 
         fn init(opcode: Opcode, rd: Register, imm: i21) Self {
-            std.debug.assert(imm % 2 == 0);
+            std.debug.assert(imm & 1 == 0);
             const umm: u21 = @bitCast(imm);
             return .{ .j = .{
                 .opcode = opcode,
@@ -406,7 +406,7 @@ const Instruction = packed union {
                 .imm12_19 = @truncate(umm >> 12),
                 .imm11 = @truncate(umm >> 11),
                 .imm1_10 = @truncate(umm >> 1),
-                .imm20 = umm >> 20,
+                .imm20 = @intCast(umm >> 20),
             } };
         }
     };
@@ -445,8 +445,8 @@ const RegisterAllocator = struct {
         return self.allocated.get(vreg).?;
     }
 
-    fn allocate(self: *RegisterAllocator, vreg: compile.VReg) ?Register {
-        const reg = self.available.pop() orelse return null;
+    fn allocate(self: *RegisterAllocator, vreg: compile.VReg) !Register {
+        const reg = self.available.pop() orelse return error.OutOfRegisters;
         self.allocated.putAssumeCapacityNoClobber(vreg, reg);
         return reg;
     }
@@ -511,7 +511,7 @@ const Context = struct {
     }
 
     fn genConstant(self: *Context, constant: compile.Instr.Constant) !void {
-        const reg = self.register_allocator.allocate(constant.dest) orelse return error.OutOfRegisters;
+        const reg = try self.register_allocator.allocate(constant.dest);
         try self.genConstantInner(reg, constant.value);
     }
 
@@ -519,7 +519,7 @@ const Context = struct {
         const lhs = self.register_allocator.get(bin_op.lhs);
         const rhs = self.register_allocator.get(bin_op.rhs);
         try self.maybeFreeSources(bin_op.sources());
-        const reg = self.register_allocator.allocate(bin_op.dest) orelse return error.OutOfRegisters;
+        const reg = try self.register_allocator.allocate(bin_op.dest);
         switch (bin_op.op) {
             .add => try self.emit(.add(reg, lhs, rhs)),
         }
-- 
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