diff --git a/lib/std/mem.zig b/lib/std/mem.zig
index 36e9813c2a..d3e874a211 100644
--- a/lib/std/mem.zig
+++ b/lib/std/mem.zig
@@ -1832,7 +1832,6 @@ pub fn writeIntSlice(comptime T: type, buffer: []u8, value: T, endian: Endian) v
 pub fn writeVarPackedInt(bytes: []u8, bit_offset: usize, bit_count: usize, value: anytype, endian: std.builtin.Endian) void {
     const T = @TypeOf(value);
     const uN = std.meta.Int(.unsigned, @bitSizeOf(T));
-    const Log2N = std.math.Log2Int(T);
 
     const bit_shift = @as(u3, @intCast(bit_offset % 8));
     const write_size = (bit_count + bit_shift + 7) / 8;
@@ -1861,9 +1860,9 @@ pub fn writeVarPackedInt(bytes: []u8, bit_offset: usize, bit_count: usize, value
 
     // Write first byte, using a mask to protects bits preceding bit_offset
     const head_mask = @as(u8, 0xff) >> bit_shift;
-    write_bytes[@as(usize, @intCast(i))] &= ~(head_mask << bit_shift);
-    write_bytes[@as(usize, @intCast(i))] |= @as(u8, @intCast(@as(uN, @bitCast(remaining)) & head_mask)) << bit_shift;
-    remaining >>= @as(Log2N, @intCast(@as(u4, 8) - bit_shift));
+    write_bytes[@intCast(i)] &= ~(head_mask << bit_shift);
+    write_bytes[@intCast(i)] |= @as(u8, @intCast(@as(uN, @bitCast(remaining)) & head_mask)) << bit_shift;
+    remaining = math.shr(T, remaining, @as(u4, 8) - bit_shift);
     i += delta;
 
     // Write bytes[1..bytes.len - 1]
diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index 1b8a9fbd7f..b1e5265815 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -4341,6 +4341,9 @@ fn airClz(self: *Self, inst: Air.Inst.Index) !void {
     const result = result: {
         const dst_ty = self.typeOfIndex(inst);
         const src_ty = self.typeOf(ty_op.operand);
+        if (src_ty.zigTypeTag(mod) == .Vector) return self.fail("TODO implement airClz for {}", .{
+            src_ty.fmt(mod),
+        });
 
         const src_mcv = try self.resolveInst(ty_op.operand);
         const mat_src_mcv = switch (src_mcv) {
@@ -4691,7 +4694,9 @@ fn byteSwap(self: *Self, inst: Air.Inst.Index, src_ty: Type, src_mcv: MCValue, m
     defer if (src_lock) |lock| self.register_manager.unlockReg(lock);
 
     switch (src_bits) {
-        else => unreachable,
+        else => return self.fail("TODO implement byteSwap for {}", .{
+            src_ty.fmt(mod),
+        }),
         8 => return if ((mem_ok or src_mcv.isRegister()) and
             self.reuseOperand(inst, ty_op.operand, 0, src_mcv))
             src_mcv
@@ -6093,16 +6098,16 @@ fn genShiftBinOp(
     rhs_ty: Type,
 ) !MCValue {
     const mod = self.bin_file.options.module.?;
-    if (lhs_ty.zigTypeTag(mod) == .Vector) {
-        return self.fail("TODO implement genShiftBinOp for {}", .{lhs_ty.fmtDebug()});
-    }
+    if (lhs_ty.zigTypeTag(mod) == .Vector) return self.fail("TODO implement genShiftBinOp for {}", .{
+        lhs_ty.fmt(mod),
+    });
 
     assert(rhs_ty.abiSize(mod) == 1);
 
     const lhs_abi_size = lhs_ty.abiSize(mod);
-    if (lhs_abi_size > 16) {
-        return self.fail("TODO implement genShiftBinOp for {}", .{lhs_ty.fmtDebug()});
-    }
+    if (lhs_abi_size > 16) return self.fail("TODO implement genShiftBinOp for {}", .{
+        lhs_ty.fmt(mod),
+    });
 
     try self.register_manager.getReg(.rcx, null);
     const rcx_lock = self.register_manager.lockRegAssumeUnused(.rcx);
@@ -6158,11 +6163,12 @@ fn genMulDivBinOp(
     rhs: MCValue,
 ) !MCValue {
     const mod = self.bin_file.options.module.?;
-    if (dst_ty.zigTypeTag(mod) == .Vector or dst_ty.zigTypeTag(mod) == .Float) {
-        return self.fail("TODO implement genMulDivBinOp for {}", .{dst_ty.fmtDebug()});
-    }
-    const dst_abi_size = @as(u32, @intCast(dst_ty.abiSize(mod)));
-    const src_abi_size = @as(u32, @intCast(src_ty.abiSize(mod)));
+    if (dst_ty.zigTypeTag(mod) == .Vector or dst_ty.zigTypeTag(mod) == .Float) return self.fail(
+        "TODO implement genMulDivBinOp for {}",
+        .{dst_ty.fmt(mod)},
+    );
+    const dst_abi_size: u32 = @intCast(dst_ty.abiSize(mod));
+    const src_abi_size: u32 = @intCast(src_ty.abiSize(mod));
     if (switch (tag) {
         else => unreachable,
         .mul, .mul_wrap => dst_abi_size != src_abi_size and dst_abi_size != src_abi_size * 2,