Do not enregister Return SP check (#59759)

Author: kunalspathak

src/coreclr/jit/compiler.cpp

@@ -4665,7 +4665,8 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
 #if defined(DEBUG) && defined(TARGET_XARCH)
         if (opts.compStackCheckOnRet)
         {
-            lvaReturnSpCheck                  = lvaGrabTempWithImplicitUse(false DEBUGARG("ReturnSpCheck"));
+            lvaReturnSpCheck = lvaGrabTempWithImplicitUse(false DEBUGARG("ReturnSpCheck"));
+            lvaSetVarDoNotEnregister(lvaReturnSpCheck, DoNotEnregisterReason::ReturnSpCheck);
             lvaTable[lvaReturnSpCheck].lvType = TYP_I_IMPL;
         }
 #endif // defined(DEBUG) && defined(TARGET_XARCH)
@@ -9825,6 +9826,10 @@ void Compiler::EnregisterStats::RecordLocal(const LclVarDsc* varDsc)
                 m_blockOpRet++;
                 break;
 
+            case DoNotEnregisterReason::ReturnSpCheck:
+                m_returnSpCheck++;
+                break;
+
             default:
                 unreached();
                 break;
@@ -9945,6 +9950,7 @@ void Compiler::EnregisterStats::Dump(FILE* fout) const
     PRINT_STATS(m_oneAsgRetyping, notEnreg);
     PRINT_STATS(m_swizzleArg, notEnreg);
     PRINT_STATS(m_blockOpRet, notEnreg);
+    PRINT_STATS(m_returnSpCheck, notEnreg);
 
     fprintf(fout, "\nAddr exposed details:\n");
     if (m_addrExposed == 0)

src/coreclr/jit/compiler.h

@@ -388,7 +388,8 @@ enum class DoNotEnregisterReason
     StoreBlkSrc,    // the local is used as STORE_BLK source.
     OneAsgRetyping, // fgMorphOneAsgBlockOp prevents this local from being enregister.
     SwizzleArg,     // the local is passed using LCL_FLD as another type.
-    BlockOpRet      // the struct is returned and it promoted or there is a cast.
+    BlockOpRet,     // the struct is returned and it promoted or there is a cast.
+    ReturnSpCheck   // the local is used to do SP check
 };
 
 enum class AddressExposedReason
@@ -10301,6 +10302,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
         unsigned m_oneAsgRetyping;
         unsigned m_swizzleArg;
         unsigned m_blockOpRet;
+        unsigned m_returnSpCheck;
         unsigned m_liveInOutHndlr;
         unsigned m_depField;
         unsigned m_noRegVars;

src/coreclr/jit/lclvars.cpp

@@ -2664,6 +2664,10 @@ void Compiler::lvaSetVarDoNotEnregister(unsigned varNum DEBUGARG(DoNotEnregister
             JITDUMP("return uses a block op\n");
             break;
 
+        case DoNotEnregisterReason::ReturnSpCheck:
+            JITDUMP("Used for SP check\n");
+            break;
+
         default:
             unreached();
             break;