interop: slightly rephrase BuildHFSpecificMD logic

Technically, we can always buildHFSpecificMD() if contract is active, but we
just optimize the build out in some cases. switch slightly obfuscates this
and requires having the call in two branches.

Signed-off-by: Roman Khimov <[email protected]>

pkg/core/interop/context.go

@@ -266,18 +266,16 @@ func (c *ContractMD) BuildHFSpecificMD(activeIn *config.Hardfork) {
 	}
 
 	for _, hf := range append([]config.Hardfork{config.HFDefault}, config.Hardforks...) {
-		switch {
-		case hf.Cmp(start) < 0:
+		if hf.Cmp(start) < 0 {
 			continue
-		case hf.Cmp(start) == 0:
-			c.buildHFSpecificMD(hf)
-		default:
-			if _, ok := c.ActiveHFs[hf]; !ok {
-				// Intentionally omit HFSpecificContractMD structure copying since mdCache is read-only.
-				c.mdCache[hf] = c.mdCache[hf.Prev()]
-				continue
-			}
+		}
+		_, contractHasChanges := c.ActiveHFs[hf]
+		if hf.Cmp(start) == 0 || contractHasChanges {
 			c.buildHFSpecificMD(hf)
+		} else {
+			// Optimize out MD rebuild, the contract is the same.
+			// Intentionally omit HFSpecificContractMD structure copying since mdCache is read-only.
+			c.mdCache[hf] = c.mdCache[hf.Prev()]
 		}
 	}
 }