From c4238858fa75f3f8034f4e631d75093a482657b7 Mon Sep 17 00:00:00 2001
From: MihaZupan <mihazupan.zupan1@gmail.com>
Date: Wed, 8 Jul 2026 23:27:32 +0200
Subject: [PATCH] Remove some branches in
 OptimizedInboxTextEncoder.GetIndexOfFirstCharToEncode

---
 .../Web/OptimizedInboxTextEncoder.cs          | 67 ++++++++-----------
 1 file changed, 29 insertions(+), 38 deletions(-)

diff --git a/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.cs b/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.cs
index 8b4f62b65fab5d..aa31fae7b29522 100644
--- a/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.cs
+++ b/src/libraries/System.Text.Encodings.Web/src/System/Text/Encodings/Web/OptimizedInboxTextEncoder.cs
@@ -394,61 +394,52 @@ public int GetIndexOfFirstByteToEncode(ReadOnlySpan<byte> data)
 
         public int GetIndexOfFirstCharToEncode(ReadOnlySpan<char> data)
         {
-            int asciiCharsSkipped = 0;
+            _AssertThisNotNull(); // hoist "this != null" check out of hot loop below
+
+            int idx = 0;
 
 #if NET
             // First, try calling the SIMD-enabled version.
             // The SIMD-enabled version handles only ASCII characters.
             if (data.Length >= 8)
             {
-                asciiCharsSkipped = data.IndexOfAnyExcept(_allowedAsciiChars);
+                idx = data.IndexOfAnyExcept(_allowedAsciiChars);
 
-                if ((uint)asciiCharsSkipped >= (uint)data.Length || char.IsAscii(data[asciiCharsSkipped]))
+                if ((uint)idx >= (uint)data.Length || char.IsAscii(data[idx]))
                 {
-                    // We either processed the whole span (in which case asciiCharsSkipped is -1), or we've found a disallowed ASCII char.
-                    return asciiCharsSkipped;
+                    // We either processed the whole span (in which case idx is -1), or we've found a disallowed ASCII char.
+                    return idx;
                 }
+
+                data = data.Slice(idx);
             }
 #endif
 
-            int idx = asciiCharsSkipped;
-
-            // If there's any leftover data, try consuming it now.
-
-            if ((uint)idx < (uint)data.Length)
+            // unroll the loop 8x
+            while (data.Length >= 8)
             {
-                _AssertThisNotNull(); // hoist "this != null" check out of hot loop below
-
-                // Slicing keeps the indexed accesses below provably in-bounds, so the JIT
-                // elides the bounds checks just as the previous pointer-based loop did.
-                ReadOnlySpan<char> remaining = data.Slice(idx);
-
-                // unroll the loop 8x
-                while (remaining.Length >= 8)
-                {
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[0])) { goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[1])) { idx += 1; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[2])) { idx += 2; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[3])) { idx += 3; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[4])) { idx += 4; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[5])) { idx += 5; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[6])) { idx += 6; goto Return; }
-                    if (!_allowedBmpCodePoints.IsCharAllowed(remaining[7])) { idx += 7; goto Return; }
-                    idx += 8;
-                    remaining = remaining.Slice(8);
-                }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[0])) { goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[1])) { idx += 1; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[2])) { idx += 2; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[3])) { idx += 3; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[4])) { idx += 4; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[5])) { idx += 5; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[6])) { idx += 6; goto Return; }
+                if (!_allowedBmpCodePoints.IsCharAllowed(data[7])) { idx += 7; goto Return; }
+                idx += 8;
+                data = data.Slice(8);
+            }
 
-                foreach (char c in remaining)
-                {
-                    if (!_allowedBmpCodePoints.IsCharAllowed(c)) { goto Return; }
-                    idx++;
-                }
+            foreach (char c in data)
+            {
+                if (!_allowedBmpCodePoints.IsCharAllowed(c)) { goto Return; }
+                idx++;
             }
 
-        Return:
+            return -1;
 
-            Debug.Assert(0 <= idx && idx <= data.Length);
-            return (idx == data.Length) ? -1 : idx;
+        Return:
+            return idx;
         }
 
         /// <summary>