JIT: Add GT_SWIFT_ERROR_RET to represent loading error register upon return

src/coreclr/jit/flowgraph.cpp

@@ -2632,7 +2632,7 @@ PhaseStatus Compiler::fgAddSwiftErrorReturns()
             {
                 assert(genReturnErrorLocal == BAD_VAR_NUM);
                 genReturnErrorLocal = lvaGrabTemp(true DEBUGARG("Single return block SwiftError value"));
-                lvaGetDesc(genReturnErrorLocal)->lvType = genActualType(TYP_I_IMPL);
+                lvaGetDesc(genReturnErrorLocal)->lvType = TYP_I_IMPL;
                 ret->AsOp()->gtOp1                      = gtNewLclvNode(genReturnErrorLocal, TYP_I_IMPL);
             }
             else

src/coreclr/jit/ifconversion.cpp

@@ -140,16 +140,7 @@ bool OptIfConversionDsc::IfConvertCheckThenFlow()
             if (thenBlock->KindIs(BBJ_RETURN))
             {
                 assert(m_finalBlock == nullptr);
-#ifdef SWIFT_SUPPORT
-                if (m_comp->lvaSwiftErrorArg != BAD_VAR_NUM)
-                {
-                    m_mainOper = GT_SWIFT_ERROR_RET;
-                }
-                else
-#endif // SWIFT_SUPPORT
-                {
-                    m_mainOper = GT_RETURN;
-                }
+                m_mainOper = GT_RETURN;
             }
             else
             {
@@ -586,7 +577,7 @@ bool OptIfConversionDsc::optIfConvert()
     {
         return false;
     }
-    assert(m_thenOperation.node->OperIs(GT_STORE_LCL_VAR, GT_RETURN, GT_SWIFT_ERROR_RET));
+    assert(m_thenOperation.node->OperIs(GT_STORE_LCL_VAR, GT_RETURN));
     if (m_doElseConversion)
     {
         if (!IfConvertCheckStmts(m_startBlock->GetTrueTarget(), &m_elseOperation))
@@ -644,7 +635,7 @@ bool OptIfConversionDsc::optIfConvert()
         }
         else
         {
-            assert((m_mainOper == GT_RETURN) || (m_mainOper == GT_SWIFT_ERROR_RET));
+            assert(m_mainOper == GT_RETURN);
             thenCost = m_thenOperation.node->AsOp()->GetReturnValue()->GetCostEx();
             if (m_doElseConversion)
             {
@@ -704,7 +695,7 @@ bool OptIfConversionDsc::optIfConvert()
     }
     else
     {
-        assert((m_mainOper == GT_RETURN) || (m_mainOper == GT_SWIFT_ERROR_RET));
+        assert(m_mainOper == GT_RETURN);
         assert(m_doElseConversion);
         assert(m_thenOperation.node->TypeGet() == m_elseOperation.node->TypeGet());
 

src/coreclr/jit/lower.cpp

@@ -521,11 +521,8 @@ GenTree* Lowering::LowerNode(GenTree* node)
             break;
 
         case GT_SWIFT_ERROR_RET:
-            LowerNode(node->gtGetOp1());
-
-            FALLTHROUGH;
         case GT_RETURN:
-            LowerRet(node->AsUnOp());
+            LowerRet(node->AsOp());
             break;
 
         case GT_RETURNTRAP:
@@ -4545,16 +4542,16 @@ void Lowering::LowerJmpMethod(GenTree* jmp)
     }
 }
 
-// Lower GT_RETURN node to insert PInvoke method epilog if required.
-void Lowering::LowerRet(GenTreeUnOp* ret)
+// Lower GT_RETURN/GT_SWIFT_ERROR_RET node to insert PInvoke method epilog if required.
+void Lowering::LowerRet(GenTreeOp* ret)
 {
     assert(ret->OperIs(GT_RETURN, GT_SWIFT_ERROR_RET));
 
     JITDUMP("lowering return node\n");
     DISPNODE(ret);
     JITDUMP("============\n");
 
-    GenTree* retVal = ret->AsOp()->GetReturnValue();
+    GenTree* retVal = ret->GetReturnValue();
     // There are two kinds of retyping:
     // - A simple bitcast can be inserted when:
     //   - We're returning a floating type as an integral type or vice-versa, or
@@ -4576,7 +4573,7 @@ void Lowering::LowerRet(GenTreeUnOp* ret)
 #endif
 
         GenTree* bitcast = comp->gtNewBitCastNode(ret->TypeGet(), retVal);
-        ret->AsOp()->SetReturnValue(bitcast);
+        ret->SetReturnValue(bitcast);
         BlockRange().InsertBefore(ret, bitcast);
         ContainCheckBitCast(bitcast);
     }

src/coreclr/jit/lower.h

@@ -154,7 +154,7 @@ class Lowering final : public Phase
     bool       TryLowerConditionToFlagsNode(GenTree* parent, GenTree* condition, GenCondition* code);
     GenTreeCC* LowerNodeCC(GenTree* node, GenCondition condition);
     void       LowerJmpMethod(GenTree* jmp);
-    void       LowerRet(GenTreeUnOp* ret);
+    void       LowerRet(GenTreeOp* ret);
     void       LowerStoreLocCommon(GenTreeLclVarCommon* lclVar);
     void       LowerRetStruct(GenTreeUnOp* ret);
     void       LowerRetSingleRegStructLclVar(GenTreeUnOp* ret);

src/coreclr/jit/morph.cpp

@@ -8755,6 +8755,18 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac, bool* optA
             if (fgGlobalMorph && varTypeIsSmall(info.compRetType) && (retVal != nullptr) && !retVal->TypeIs(TYP_VOID) &&
                 fgCastNeeded(retVal, info.compRetType))
             {
+#ifdef SWIFT_SUPPORT
+                // Morph error operand if tree is a GT_SWIFT_ERROR_RET node
+                if (tree->OperIs(GT_SWIFT_ERROR_RET))
+                {
+                    GenTree* const errorVal = fgMorphTree(tree->gtGetOp1());
+                    tree->AsOp()->gtOp1     = errorVal;
+
+                    // Propagate side effect flags
+                    tree->SetAllEffectsFlags(errorVal);
+                }
+#endif // SWIFT_SUPPORT
+
                 // Small-typed return values are normalized by the callee
                 retVal = gtNewCastNode(TYP_INT, retVal, false, info.compRetType);