improve Shl,Shr,Shrs documentation

diff --git a/scripts/ir_spec.py b/scripts/ir_spec.py
index 4525974..c998ebe 100755 (executable)
--- a/scripts/ir_spec.py
+++ b/scripts/ir_spec.py
@@ -813,18 +813,27 @@ class Sel(Op):
 
 class Shl(Binop):
        """Returns its first operands bits shifted left by the amount of the 2nd
-       operand"""
+       operand.
+       The right input (shift amount) must be an unsigned integer value.
+       If the result mode has modulo_shift!=0, then the effective shift amount is
+       the right input modulo this modulo_shift amount."""
        flags = []
 
 class Shr(Binop):
        """Returns its first operands bits shifted right by the amount of the 2nd
-       operand. No special handling for the sign bit (zero extension)"""
+       operand. No special handling for the sign bit is performed (zero extension).
+       The right input (shift amount) must be an unsigned integer value.
+       If the result mode has modulo_shift!=0, then the effective shift amount is
+       the right input modulo this modulo_shift amount."""
        flags = []
 
 class Shrs(Binop):
        """Returns its first operands bits shifted right by the amount of the 2nd
        operand. The leftmost bit (usually the sign bit) stays the same
-       (sign extension)"""
+       (sign extension).
+       The right input (shift amount) must be an unsigned integer value.
+       If the result mode has modulo_shift!=0, then the effective shift amount is
+       the right input modulo this modulo_shift amount."""
        flags = []
 
 class Start(Op):