Optimize small bases.

libsolidity/codegen/YulUtilFunctions.cpp

@@ -618,9 +618,28 @@ string YulUtilFunctions::overflowCheckedIntExpFunction(
 					eq(exponent, 1)
 				) { power := base leave }
 
-				power := 1
+
 				let max := <maxValue>
 
+				// small base optimizations
+				if eq(base, 2) {
+					if gt(exponent, 255) { revert(0, 0) }
+					power := exp(2, exponent)
+					if gt(power, max) { revert(0, 0) }
+					leave
+				}
+				// b**e < 2**256 <=> e * log(b) < 256 * log(2) <=> e < 256 * log(2) / log(b)
+				if or(
+					and(lt(base, 11), lt(exponent, 78)),
+					and(lt(base, 257), lt(exponent, 32))
+				) {
+					power := exp(base, exponent)
+					if gt(power, max) { revert(0, 0) }
+					leave
+				}
+
+				power := 1
+
 				for { } gt(exponent, 1) {} {
 					// overflow check for base * base
 					<?signed>