Masking away eGPR from GCREf nodes

Author: DeepakRajendrakumaran

src/coreclr/jit/lsrabuild.cpp

@@ -2835,6 +2835,22 @@ void LinearScan::buildInitialParamDef(const LclVarDsc* varDsc, regNumber paramRe
     Interval*        interval = getIntervalForLocalVar(varDsc->lvVarIndex);
     const var_types  regType  = varDsc->GetRegisterType();
     SingleTypeRegSet mask     = allRegs(regType);
+#ifdef TARGET_AMD64
+    if (varTypeIsGC(regType))
+    {
+#ifdef DEBUG
+        if (VERBOSE)
+        {
+            printf("\n\n buildInitialParamDef : \n");
+
+            //compiler->gtDispTree(tree, nullptr, nullptr, true);
+            printf("(GC type)\n\n");
+        }
+#endif // DEBUG
+        assert((mask & lowGprRegs) != RBM_NONE);
+        mask &= lowGprRegs;
+    }
+#endif // TARGET_AMD64
     if ((paramReg != REG_NA) && !stressInitialParamReg())
     {
         // Set this interval as currently assigned to that register
@@ -3079,6 +3095,30 @@ RefPosition* LinearScan::BuildDef(GenTree* tree, SingleTypeRegSet dstCandidates,
         interval->hasInterferingUses = true;
         // pendingDelayFree = false;
     }
+#ifdef TARGET_AMD64
+    if (varTypeIsGC(tree->TypeGet()))
+    {
+#ifdef DEBUG
+        if (VERBOSE)
+        {
+            printf("\n\n BuildDef: tree : \n");
+
+            compiler->gtDispTree(tree, nullptr, nullptr, true);
+            printf("(GC type)\n\n");
+        }
+#endif // DEBUG
+        if (dstCandidates == RBM_NONE)
+        {
+            dstCandidates = lowGprRegs;
+        }
+        else
+        {
+            // If we have a candidate register, it must be a low GPR.
+            assert((dstCandidates & lowGprRegs) != RBM_NONE);
+            dstCandidates &= lowGprRegs;
+        }
+    }
+#endif // TARGET_AMD64
     RefPosition* defRefPosition =
         newRefPosition(interval, currentLoc + 1, RefTypeDef, tree, dstCandidates, multiRegIdx);
     if (tree->IsUnusedValue())
@@ -4016,9 +4056,26 @@ void LinearScan::BuildStoreLocDef(GenTreeLclVarCommon* storeLoc,
     {
         defCandidates = allRegs(type);
     }
+#elif TARGET_AMD64
+    defCandidates = allRegs(type);
+    //if (varTypeIsGC(type))
+    if (varTypeUsesIntReg(type))
+    {
+#ifdef DEBUG
+        if (VERBOSE)
+        {
+            printf("\n\n BuildStoreLocDef : \n");
+
+            //compiler->gtDispTree(tree, nullptr, nullptr, true);
+            printf("(GC type)\n\n");
+        }
+#endif // DEBUG
+        assert((defCandidates & lowGprRegs) != RBM_NONE);
+        defCandidates &= lowGprRegs;
+    }
 #else
     defCandidates = allRegs(type);
-#endif // TARGET_X86
+#endif
 
     RefPosition* def = newRefPosition(varDefInterval, currentLoc + 1, RefTypeDef, storeLoc, defCandidates, index);
     if (varDefInterval->isWriteThru)

src/coreclr/jit/lsraxarch.cpp

@@ -299,10 +299,33 @@ int LinearScan::BuildNode(GenTree* tree)
         case GT_AND:
         case GT_OR:
         case GT_XOR:
+        {
             srcCount = BuildBinaryUses(tree->AsOp());
             assert(dstCount == 1);
+#ifdef TARGET_AMD64
+            GenTree* op1 = tree->AsOp()->gtGetOp1();
+            GenTree* op2 = tree->AsOp()->gtGetOp2IfPresent();
+            if ((op1 != nullptr) && (varTypeIsGC(op1->TypeGet()))
+                || (op2 != nullptr) && (varTypeIsGC(op2->TypeGet())))
+            {
+                // If either operand is a GC type, we need to use a low GPR.
+#ifdef DEBUG
+                if (VERBOSE)
+                {
+                    printf("\n\n BuildBinary: tree : \n");
+
+                    compiler->gtDispTree(tree, nullptr, nullptr, true);
+                    printf("(GC type)\n\n");
+                }
+#endif // DEBUG
+                // For GC types, we always use a low GPR.
+                BuildDef(tree, lowGprRegs);
+                break;
+            }
+#endif // TARGET_AMD64
             BuildDef(tree);
             break;
+        }
 
         case GT_RETURNTRAP:
         {
@@ -3109,7 +3132,11 @@ int LinearScan::BuildIndir(GenTreeIndir* indirTree)
 #endif // FEATURE_SIMD
 
 #ifdef TARGET_AMD64
-    if (varTypeUsesIntReg(indirTree->Addr()))
+    if (/*indirTree->OperIs(GT_STOREIND) && */varTypeIsGC(indirTree->Addr()->TypeGet()))
+    {
+        useCandidates = lowGprRegs; // StoreIndir with GC type address must use low GPRs
+    }
+    else if (varTypeUsesIntReg(indirTree->Addr()))
     {
         useCandidates = ForceLowGprForApxIfNeeded(indirTree->Addr(), useCandidates, getEvexIsSupported());
     }