ei + ret -> reti

1 files changed, 19 insertions, 0 deletions

diff --git a/Optimizing-assembly-code.md b/Optimizing-assembly-code.md
index 0c5e733..9d27bde 100644
--- a/Optimizing-assembly-code.md
+++ b/Optimizing-assembly-code.md
@@ -62,6 +62,7 @@ WikiTI's advice fully applies here:
   - [Conditional return](#conditional-return)
   - [Conditional call](#conditional-call)
   - [Conditional `rst $38`](#conditional-rst-38)
+  - [Enable interrupts and return](#enable-interrupts-and-return)
 - [Jump and lookup tables](#jump-and-lookup-tables)
   - [Chain comparisons](#chain-comparisons)
 
@@ -1841,6 +1842,24 @@ But do:
 (The label `@` evaluates to the current `pc` value, which in `jr z, @ + 1` is right before the `jr` instruction. The instruction consists of two bytes, the opcode and the relative offset. `@ + 1` evaluates to in-between those two bytes. The `jr` instruction encodes its offset relative to the *end* of the instruction, i.e. the *next* `pc` value after the instruction has been read, so the relative offset is `-1`, aka `$ff`.)
 
 
+### Enable interrupts and return
+
+Don't do:
+
+```asm
+	; 2 bytes, 5 cycles
+	ei
+	ret
+```
+
+But do:
+
+```asm
+	; 1 byte, 4 cycles
+	reti
+```
+
+
 ## Jump and lookup tables