diff --git a/src/crt/i48shrs_1.src b/src/crt/i48shrs_1.src
index a1825becd..b84b4d4df 100644
--- a/src/crt/i48shrs_1.src
+++ b/src/crt/i48shrs_1.src
@@ -5,6 +5,12 @@
 	.type	__i48shrs_1, @function
 
 __i48shrs_1:
+	; Input:
+	; - UDE:UHL
+	; Output:
+	; - UDE:UHL >>= 1 (signed)
+	; - Carry = shifted-out bit
+	; Cost: 24 bytes | 25F + 11R + 8W + 3
 	push	hl
 	scf
 	sbc	hl, hl
diff --git a/src/crt/i48shru_1.src b/src/crt/i48shru_1.src
index 6159a9848..05f58f495 100644
--- a/src/crt/i48shru_1.src
+++ b/src/crt/i48shru_1.src
@@ -5,6 +5,12 @@
 	.type	__i48shru_1, @function
 
 __i48shru_1:
+	; Input:
+	; - UDE:UHL
+	; Output:
+	; - UDE:UHL >>= 1 (unsigned)
+	; - Carry = shifted-out bit
+	; Cost: 24 bytes | 25F + 11R + 8W + 3
 	push	hl
 	scf
 	sbc	hl, hl
diff --git a/src/crt/ishrs_1.src b/src/crt/ishrs_1.src
index d1464ba72..48890e27a 100644
--- a/src/crt/ishrs_1.src
+++ b/src/crt/ishrs_1.src
@@ -5,6 +5,12 @@
 	.type	__ishrs_1, @function
 
 __ishrs_1:
+	; Input:
+	; - UHL
+	; Output:
+	; - UHL >>= 1 (signed)
+	; - Carry = shifted-out bit
+	; Cost: 14 bytes | 15F + 7R + 4W + 2
 	push	hl
 	ld	hl, 2
 	add	hl, sp
diff --git a/src/crt/ishru_1.src b/src/crt/ishru_1.src
index a88c783d5..d81cd0b65 100644
--- a/src/crt/ishru_1.src
+++ b/src/crt/ishru_1.src
@@ -5,6 +5,12 @@
 	.type	__ishru_1, @function
 
 __ishru_1:
+	; Input:
+	; - UHL
+	; Output:
+	; - UHL >>= 1 (unsigned)
+	; - Carry = shifted-out bit
+	; Cost: 14 bytes | 15F + 7R + 4W + 2
 	push	hl
 	ld	hl, 2
 	add	hl, sp
diff --git a/src/crt/llshl_1.src b/src/crt/llshl_1.src
index dfb491ca7..368e880ed 100644
--- a/src/crt/llshl_1.src
+++ b/src/crt/llshl_1.src
@@ -5,6 +5,12 @@
 	.type	__llshl_1, @function
 
 __llshl_1:
+	; Input:
+	; - BC:UDE:UHL
+	; Output:
+	; - BC:UDE:UHL <<= 1
+	; - Carry = shifted-out bit
+	; Cost: 10 bytes | 11F + 3R + 1
 	add	hl, hl
 	ex	de, hl
 	adc	hl, hl
diff --git a/src/crt/llshrs_1.src b/src/crt/llshrs_1.src
index 0e6e2d786..e999d26b8 100644
--- a/src/crt/llshrs_1.src
+++ b/src/crt/llshrs_1.src
@@ -5,6 +5,12 @@
 	.type	__llshrs_1, @function
 
 __llshrs_1:
+	; Input:
+	; - BC:UDE:UHL
+	; Output:
+	; - BC:UDE:UHL >>= 1 (signed)
+	; - Carry = shifted-out bit
+	; Cost: 28 bytes | 29F + 11R + 8W + 3
 	push	hl
 	scf
 	sbc	hl, hl
diff --git a/src/crt/llshru_1.src b/src/crt/llshru_1.src
index 487c9362d..5d0dc9400 100644
--- a/src/crt/llshru_1.src
+++ b/src/crt/llshru_1.src
@@ -5,6 +5,12 @@
 	.type	__llshru_1, @function
 
 __llshru_1:
+	; Input:
+	; - BC:UDE:UHL
+	; Output:
+	; - BC:UDE:UHL >>= 1 (unsigned)
+	; - Carry = shifted-out bit
+	; Cost: 28 bytes | 29F + 11R + 8W + 3
 	push	hl
 	scf
 	sbc	hl, hl
diff --git a/src/crt/lshrs_1.src b/src/crt/lshrs_1.src
index cc47736ef..d54caeac5 100644
--- a/src/crt/lshrs_1.src
+++ b/src/crt/lshrs_1.src
@@ -5,6 +5,12 @@
 	.type	__lshrs_1, @function
 
 __lshrs_1:
+	; Input:
+	; - E:UHL
+	; Output:
+	; - E:UHL >>= 1 (signed)
+	; - Carry = shifted-out bit
+	; Cost: 16 bytes | 17F + 7R + 4W + 2
 	push	hl
 	ld	hl, 2
 	add	hl, sp
diff --git a/src/crt/lshru_1.src b/src/crt/lshru_1.src
index 8aa1bb3ae..5e7c47af7 100644
--- a/src/crt/lshru_1.src
+++ b/src/crt/lshru_1.src
@@ -5,6 +5,12 @@
 	.type	__lshru_1, @function
 
 __lshru_1:
+	; Input:
+	; - E:UHL
+	; Output:
+	; - E:UHL >>= 1 (unsigned)
+	; - Carry = shifted-out bit
+	; Cost: 16 bytes | 17F + 7R + 4W + 2
 	push	hl
 	ld	hl, 2
 	add	hl, sp