From 8889ef2f0704b6939eceb39f32a44686be3f8c6c Mon Sep 17 00:00:00 2001
From: Vladimir Panteleev <git@thecybershadow.net>
Date: Sat, 24 Nov 2018 08:30:14 +0000
Subject: [PATCH] std.string: Optimize indexOf with start index a bit

Use of early returns improves readability and reduces the instruction
count in DMD's output.
---
 std/string.d | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/std/string.d b/std/string.d
index f9ce503f1..44e714f69 100644
--- a/std/string.d
+++ b/std/string.d
@@ -895,15 +895,12 @@ ptrdiff_t indexOf(Char1, Char2)(const(Char1)[] s, const(Char2)[] sub,
 @safe
 if (isSomeChar!Char1 && isSomeChar!Char2)
 {
-    if (startIdx < s.length)
-    {
-        ptrdiff_t foundIdx = indexOf(s[startIdx .. $], sub);
-        if (foundIdx != -1)
-        {
-            return foundIdx + cast(ptrdiff_t) startIdx;
-        }
-    }
-    return -1;
+    if (startIdx >= s.length)
+        return -1;
+    ptrdiff_t foundIdx = indexOf(s[startIdx .. $], sub);
+    if (foundIdx == -1)
+        return -1;
+    return foundIdx + cast(ptrdiff_t) startIdx;
 }
 
 /// Ditto
@@ -912,15 +909,12 @@ ptrdiff_t indexOf(Char1, Char2)(const(Char1)[] s, const(Char2)[] sub,
 @safe
 if (isSomeChar!Char1 && isSomeChar!Char2)
 {
-    if (startIdx < s.length)
-    {
-        ptrdiff_t foundIdx = indexOf(s[startIdx .. $], sub, cs);
-        if (foundIdx != -1)
-        {
-            return foundIdx + cast(ptrdiff_t) startIdx;
-        }
-    }
-    return -1;
+    if (startIdx >= s.length)
+        return -1;
+    ptrdiff_t foundIdx = indexOf(s[startIdx .. $], sub, cs);
+    if (foundIdx == -1)
+        return -1;
+    return foundIdx + cast(ptrdiff_t) startIdx;
 }
 
 ///