From 2043bcedc45a2136ce37c1fa00a657b6ad093c13 Mon Sep 17 00:00:00 2001
From: Max Charlamb <44248479+max-charlamb@users.noreply.github.com>
Date: Wed, 3 Dec 2025 11:19:44 -0500
Subject: [PATCH] fix debuginfo var numbering

---
 src/coreclr/jit/lclvars.cpp | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/coreclr/jit/lclvars.cpp b/src/coreclr/jit/lclvars.cpp
index 85e9da7678a2f5..19d21482f219c2 100644
--- a/src/coreclr/jit/lclvars.cpp
+++ b/src/coreclr/jit/lclvars.cpp
@@ -1126,18 +1126,21 @@ unsigned Compiler::compMap2ILvarNum(unsigned varNum) const
         return (unsigned)ICorDebugInfo::UNKNOWN_ILNUM;
     }
 
+    unsigned originalVarNum = varNum;
+
     // Now mutate varNum to remove extra parameters from the count.
-    if (((info.compMethodInfo->args.callConv & CORINFO_CALLCONV_PARAMTYPE) != 0) && (varNum > info.compTypeCtxtArg))
+    if (((info.compMethodInfo->args.callConv & CORINFO_CALLCONV_PARAMTYPE) != 0) &&
+        (originalVarNum > info.compTypeCtxtArg))
     {
         varNum--;
     }
 
-    if (info.compIsVarArgs && (varNum > lvaVarargsHandleArg))
+    if (info.compIsVarArgs && (originalVarNum > lvaVarargsHandleArg))
     {
         varNum--;
     }
 
-    if ((lvaAsyncContinuationArg != BAD_VAR_NUM) && (varNum > lvaAsyncContinuationArg))
+    if ((lvaAsyncContinuationArg != BAD_VAR_NUM) && (originalVarNum > lvaAsyncContinuationArg))
     {
         varNum--;
     }
@@ -1145,7 +1148,7 @@ unsigned Compiler::compMap2ILvarNum(unsigned varNum) const
     // Is there a hidden argument for the return buffer. Note that this code
     // works because if the RetBuffArg is not present, compRetBuffArg will be
     // BAD_VAR_NUM
-    if ((info.compRetBuffArg != BAD_VAR_NUM) && (varNum > info.compRetBuffArg))
+    if ((info.compRetBuffArg != BAD_VAR_NUM) && (originalVarNum > info.compRetBuffArg))
     {
         varNum--;
     }