Create final IG before clearing GC info

src/coreclr/jit/codegenlinear.cpp

@@ -835,28 +835,29 @@ void CodeGen::genCodeForBBlist()
 #endif // DEBUG
     }  //------------------ END-FOR each block of the method -------------------
 
-    // There could be variables alive at this point. For example see lvaKeepAliveAndReportThis.
-    // This call is for cleaning the GC refs
-    genUpdateLife(VarSetOps::MakeEmpty(compiler));
-
 #if !defined(FEATURE_EH_FUNCLETS)
     // If this is a synchronized method on x86, and we generated all the code without
     // generating the "exit monitor" call, then we must have deleted the single return block
     // with that call because it was dead code. We still need to report the monitor range
     // to the VM in the GC info, so create a label at the very end so we have a marker for
     // the monitor end range.
+    //
+    // Do this before cleaning the GC refs below; we don't want to create an IG that clears
+    // the `this` pointer for lvaKeepAliveAndReportThis.
 
     if ((compiler->info.compFlags & CORINFO_FLG_SYNCH) && (compiler->syncEndEmitCookie == nullptr))
     {
         JITDUMP("Synchronized method with missing exit monitor call; adding final label\n");
-
-        // The GC liveness sets should all be empty.
         compiler->syncEndEmitCookie =
             GetEmitter()->emitAddLabel(gcInfo.gcVarPtrSetCur, gcInfo.gcRegGCrefSetCur, gcInfo.gcRegByrefSetCur);
         noway_assert(compiler->syncEndEmitCookie != nullptr);
     }
 #endif // !FEATURE_EH_FUNCLETS
 
+    // There could be variables alive at this point. For example see lvaKeepAliveAndReportThis.
+    // This call is for cleaning the GC refs
+    genUpdateLife(VarSetOps::MakeEmpty(compiler));
+
     /* Finalize the spill  tracking logic */
 
     regSet.rsSpillEnd();

src/coreclr/jit/compiler.hpp

@@ -2320,7 +2320,7 @@ inline void LclVarDsc::incRefCnts(weight_t weight, Compiler* comp, RefCountState
 
 inline bool Compiler::lvaKeepAliveAndReportThis()
 {
-    if (info.compIsStatic || lvaTable[0].TypeGet() != TYP_REF)
+    if (info.compIsStatic || (lvaTable[0].TypeGet() != TYP_REF))
     {
         return false;
     }
@@ -2354,7 +2354,7 @@ inline bool Compiler::lvaKeepAliveAndReportThis()
     // We keep it alive in the lookup scenario, even when the VM didn't ask us to,
     // because collectible types need the generics context when gc-ing.
     //
-    // Methoods that can inspire OSR methods must always report context as live
+    // Methods that can inspire OSR methods must always report context as live
     //
     if (genericsContextIsThis)
     {