From dd4af0b65af3537c0f566ebb3a1d837b448d33ee Mon Sep 17 00:00:00 2001
From: SingleAccretion <AccretionMail@yandex.ru>
Date: Fri, 27 Mar 2026 00:26:52 +0300
Subject: [PATCH] Coalesce adjacent no-GC regions on x86

---
 src/coreclr/jit/gcencode.cpp | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/coreclr/jit/gcencode.cpp b/src/coreclr/jit/gcencode.cpp
index 24c4c3196a54e4..40908eccefa695 100644
--- a/src/coreclr/jit/gcencode.cpp
+++ b/src/coreclr/jit/gcencode.cpp
@@ -2124,21 +2124,35 @@ unsigned PendingArgsStack::pasEnumGCoffs(unsigned iter, unsigned* offs)
 // when reporting interruptible ranges.
 class NoGCRegionEncoder
 {
-    BYTE* dest;
+    BYTE*    dest;
+    unsigned lastSize    = 0;
+    unsigned lastEndOffs = -1;
 public:
-    size_t totalSize;
+    size_t totalSize = 0;
 
     NoGCRegionEncoder(BYTE* dest)
         : dest(dest)
-        , totalSize(0)
     {
     }
 
     // This callback is called for each insGroup marked with IGF_NOGCINTERRUPT.
     bool operator()(unsigned igFuncIdx, unsigned igOffs, unsigned igSize, unsigned firstInstrSize, bool isInProlog)
     {
-        totalSize += encodeUnsigned(dest == NULL ? NULL : dest + totalSize, igOffs);
-        totalSize += encodeUnsigned(dest == NULL ? NULL : dest + totalSize, igSize);
+        unsigned size;
+        if (igOffs == lastEndOffs) // Coalesce adjacent intervals by re-encoding the enlarged size.
+        {
+            totalSize -= encodeUnsigned(nullptr, lastSize);
+            size = lastSize + igSize;
+        }
+        else
+        {
+            totalSize += encodeUnsigned(dest == nullptr ? nullptr : dest + totalSize, igOffs);
+            size = igSize;
+        }
+        totalSize += encodeUnsigned(dest == nullptr ? nullptr : dest + totalSize, size);
+
+        lastSize    = size;
+        lastEndOffs = igOffs + igSize;
         return true;
     }
 };