No retyping arm/arm64.

src/coreclr/src/jit/compiler.h

@@ -9161,6 +9161,36 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
         return varTypeIsStruct(info.compRetNativeType) && (info.compRetBuffArg == BAD_VAR_NUM);
 #endif // TARGET_XXX
 
+#else // not FEATURE_MULTIREG_RET
+
+        // For this architecture there are no multireg returns
+        return false;
+
+#endif // FEATURE_MULTIREG_RET
+    }
+
+    // Returns true if the method returns a value in more than one return register,
+    // it should replace/be  merged with compMethodReturnsMultiRegRetType when #36868 is fixed.
+    bool compMethodReturnsResInMultiplyRegisters()
+    {
+#if FEATURE_MULTIREG_RET
+#if defined(TARGET_X86)
+        // On x86 only 64-bit longs are returned in multiple registers
+        return varTypeIsLong(info.compRetNativeType);
+#else // targets: X64-UNIX, ARM64 or ARM32
+#if defined(TARGET_ARM64)
+        // TYP_SIMD16 is returned in one register.
+        if (info.compRetNativeType == TYP_SIMD16)
+        {
+            return false;
+        }
+#endif
+        // On all other targets that support multireg return values:
+        // Methods returning a struct in multiple registers have a return value of TYP_STRUCT.
+        // Such method's compRetNativeType is TYP_STRUCT without a hidden RetBufArg
+        return varTypeIsStruct(info.compRetNativeType) && (info.compRetBuffArg == BAD_VAR_NUM);
+#endif // TARGET_XXX
+
 #else // not FEATURE_MULTIREG_RET
 
         // For this architecture there are no multireg returns

src/coreclr/src/jit/gentree.cpp

@@ -15149,6 +15149,11 @@ GenTree* Compiler::gtNewTempAssign(
             assert(tmp == genReturnLocal);
             ok = true;
         }
+        else if (varTypeIsSIMD(dstTyp) && (valTyp == TYP_STRUCT))
+        {
+            assert(val->IsCall());
+            ok = true;
+        }
 
         if (!ok)
         {

src/coreclr/src/jit/gentree.h

@@ -4257,13 +4257,7 @@ struct GenTreeCall final : public GenTree
         {
             return true;
         }
-#elif defined(FEATURE_HFA) && defined(TARGET_ARM64)
-        // SIMD types are returned in vector regs on ARM64.
-        if (varTypeIsSIMD(gtType))
-        {
-            return false;
-        }
-#endif // FEATURE_HFA && TARGET_ARM64
+#endif
 
         if (!varTypeIsStruct(gtType) || HasRetBufArg())
         {

src/coreclr/src/jit/importer.cpp

@@ -803,7 +803,7 @@ void Compiler::impAssignTempGen(unsigned             tmpNum,
         var_types varType = lvaTable[tmpNum].lvType;
         assert(tiVerificationNeeded || varType == TYP_UNDEF || varTypeIsStruct(varType));
         lvaSetStruct(tmpNum, structType, false);
-
+        varType = lvaTable[tmpNum].lvType;
         // Now, set the type of the struct value. Note that lvaSetStruct may modify the type
         // of the lclVar to a specialized type (e.g. TYP_SIMD), based on the handle (structType)
         // that has been passed in for the value being assigned to the temp, in which case we
@@ -812,9 +812,12 @@ void Compiler::impAssignTempGen(unsigned             tmpNum,
         // type, this would not be necessary - but that requires additional JIT/EE interface
         // calls that may not actually be required - e.g. if we only access a field of a struct.
 
-        val->gtType = lvaTable[tmpNum].lvType;
+        if (compDoOldStructRetyping())
+        {
+            val->gtType = varType;
+        }
 
-        GenTree* dst = gtNewLclvNode(tmpNum, val->gtType);
+        GenTree* dst = gtNewLclvNode(tmpNum, varType);
         asg          = impAssignStruct(dst, val, structType, curLevel, pAfterStmt, ilOffset, block);
     }
     else
@@ -1224,7 +1227,7 @@ GenTree* Compiler::impAssignStructPtr(GenTree*             destAddr,
                     lcl->gtFlags |= GTF_DONT_CSE;
                     varDsc->lvIsMultiRegRet = true;
                 }
-                else if (lcl->gtType != src->gtType)
+                else if ((lcl->gtType != src->gtType) && compDoOldStructRetyping())
                 {
                     // We change this to a GT_LCL_FLD (from a GT_ADDR of a GT_LCL_VAR)
                     lcl->ChangeOper(GT_LCL_FLD);
@@ -1434,7 +1437,7 @@ GenTree* Compiler::impAssignStructPtr(GenTree*             destAddr,
             dest = gtNewOperNode(GT_IND, asgType, destAddr);
         }
     }
-    else
+    else if (compDoOldStructRetyping())
     {
         dest->gtType = asgType;
     }
@@ -8011,7 +8014,7 @@ var_types Compiler::impImportCall(OPCODE                  opcode,
 
     CORINFO_CLASS_HANDLE actualMethodRetTypeSigClass;
     actualMethodRetTypeSigClass = sig->retTypeSigClass;
-    if (varTypeIsStruct(callRetTyp))
+    if (varTypeIsStruct(callRetTyp) && compDoOldStructRetyping())
     {
         callRetTyp   = impNormStructType(actualMethodRetTypeSigClass);
         call->gtType = callRetTyp;
@@ -16656,7 +16659,14 @@ bool Compiler::impReturnInstruction(int prefixFlags, OPCODE& opcode)
                     impAssignTempGen(lvaInlineeReturnSpillTemp, op2, se.seTypeInfo.GetClassHandle(),
                                      (unsigned)CHECK_SPILL_ALL);
 
-                    GenTree* tmpOp2 = gtNewLclvNode(lvaInlineeReturnSpillTemp, op2->TypeGet());
+                    var_types lclRetType = op2->TypeGet();
+                    if (!compDoOldStructRetyping())
+                    {
+                        LclVarDsc* varDsc = lvaGetDesc(lvaInlineeReturnSpillTemp);
+                        lclRetType        = varDsc->lvType;
+                    }
+
+                    GenTree* tmpOp2 = gtNewLclvNode(lvaInlineeReturnSpillTemp, lclRetType);
 
                     if (compDoOldStructRetyping())
                     {

src/coreclr/src/jit/jitconfigvalues.h

@@ -437,13 +437,8 @@ CONFIG_INTEGER(JitSaveFpLrWithCalleeSavedRegisters, W("JitSaveFpLrWithCalleeSave
 #endif // defined(TARGET_ARM64)
 #endif // DEBUG
 
-#if defined(TARGET_ARMARCH)
-CONFIG_INTEGER(JitDoOldStructRetyping, W("JitDoOldStructRetyping"), 1) // Allow Jit to retype structs as primitive types
+CONFIG_INTEGER(JitDoOldStructRetyping, W("JitDoOldStructRetyping"), 0) // Allow Jit to retype structs as primitive types
                                                                        // when possible.
-#else
-CONFIG_INTEGER(JitDoOldStructRetyping, W("JitDoOldStructRetyping"), 1) // Allow Jit to retype structs as primitive types
-                                                                       // when possible.
-#endif
 
 #undef CONFIG_INTEGER
 #undef CONFIG_STRING

src/coreclr/src/jit/lclvars.cpp

@@ -1630,6 +1630,7 @@ void Compiler::StructPromotionHelper::CheckRetypedAsScalar(CORINFO_FIELD_HANDLE
 //
 bool Compiler::StructPromotionHelper::CanPromoteStructType(CORINFO_CLASS_HANDLE typeHnd)
 {
+    assert(typeHnd != nullptr);
     if (!compiler->eeIsValueClass(typeHnd))
     {
         // TODO-ObjectStackAllocation: Enable promotion of fields of stack-allocated objects.
@@ -1865,6 +1866,7 @@ bool Compiler::StructPromotionHelper::CanPromoteStructVar(unsigned lclNum)
     }
 
     CORINFO_CLASS_HANDLE typeHnd = varDsc->lvVerTypeInfo.GetClassHandle();
+    assert(typeHnd != nullptr);
     return CanPromoteStructType(typeHnd);
 }
 

src/coreclr/src/jit/lower.cpp

@@ -2975,9 +2975,8 @@ void Lowering::LowerRet(GenTreeUnOp* ret)
             }
         }
 #endif // DEBUG
-        if (varTypeIsStruct(ret) && !comp->compMethodReturnsMultiRegRetType())
+        if (varTypeIsStruct(ret))
         {
-            assert(!comp->compDoOldStructRetyping());
             LowerRetStruct(ret);
         }
     }
@@ -3103,7 +3102,29 @@ void Lowering::LowerStoreLocCommon(GenTreeLclVarCommon* lclStore)
 //
 void Lowering::LowerRetStruct(GenTreeUnOp* ret)
 {
-    assert(!comp->compMethodReturnsMultiRegRetType());
+#if defined(FEATURE_HFA) && defined(TARGET_ARM64)
+    if (ret->TypeIs(TYP_SIMD16))
+    {
+        if (comp->info.compRetNativeType == TYP_STRUCT)
+        {
+            assert(!comp->compDoOldStructRetyping());
+            assert(ret->gtGetOp1()->TypeIs(TYP_SIMD16));
+            assert(comp->compMethodReturnsResInMultiplyRegisters());
+            ret->ChangeType(comp->info.compRetNativeType);
+        }
+        else
+        {
+            assert(comp->info.compRetNativeType == TYP_SIMD16);
+            return;
+        }
+    }
+#endif
+
+    if (comp->compMethodReturnsResInMultiplyRegisters())
+    {
+        return;
+    }
+
     assert(!comp->compDoOldStructRetyping());
     assert(ret->OperIs(GT_RETURN));
     assert(varTypeIsStruct(ret));
@@ -3190,7 +3211,7 @@ void Lowering::LowerRetStruct(GenTreeUnOp* ret)
 //
 void Lowering::LowerRetStructLclVar(GenTreeUnOp* ret)
 {
-    assert(!comp->compMethodReturnsMultiRegRetType());
+    assert(!comp->compMethodReturnsResInMultiplyRegisters());
     assert(!comp->compDoOldStructRetyping());
     assert(ret->OperIs(GT_RETURN));
     GenTreeLclVarCommon* lclVar = ret->gtGetOp1()->AsLclVar();
@@ -3271,18 +3292,31 @@ void Lowering::LowerCallStruct(GenTreeCall* call)
         return;
     }
 
-#ifdef TARGET_ARMARCH
-    // !compDoOldStructRetyping is not supported on arm yet,
-    // because of HFA.
-    assert(comp->compDoOldStructRetyping());
-    return;
-#else // !TARGET_ARMARCH
+#if defined(FEATURE_HFA)
+    if (comp->IsHfa(call))
+    {
+#if defined(TARGET_ARM64)
+        assert(comp->GetHfaCount(call) == 1);
+#elif defined(TARGET_ARM)
+        // ARM returns double in 2 float registers, but
+        // `call->HasMultiRegRetVal()` count double registers.
+        assert(comp->GetHfaCount(call) <= 2);
+#elif  // !TARGET_ARM64 && !TARGET_ARM
+        unreached();
+#endif // !TARGET_ARM64 && !TARGET_ARM
+        var_types hfaType = comp->GetHfaType(call);
+        if (call->TypeIs(hfaType))
+        {
+            return;
+        }
+    }
+#endif // FEATURE_HFA
 
     assert(!comp->compDoOldStructRetyping());
     CORINFO_CLASS_HANDLE        retClsHnd = call->gtRetClsHnd;
     Compiler::structPassingKind howToReturnStruct;
     var_types                   returnType = comp->getReturnTypeForStruct(retClsHnd, &howToReturnStruct);
-    assert(!varTypeIsStruct(returnType) && returnType != TYP_UNKNOWN);
+    assert(returnType != TYP_STRUCT && returnType != TYP_UNKNOWN);
     var_types origType = call->TypeGet();
     call->gtType       = genActualType(returnType);
 
@@ -3297,12 +3331,18 @@ void Lowering::LowerCallStruct(GenTreeCall* call)
             case GT_STORE_BLK:
             case GT_STORE_OBJ:
                 // Leave as is, the user will handle it.
-                assert(user->TypeIs(origType));
+                assert(user->TypeIs(origType) || varTypeIsSIMD(user->TypeGet()));
                 break;
 
+#ifdef FEATURE_SIMD
+            case GT_STORE_LCL_FLD:
+                assert(varTypeIsSIMD(user) && (returnType == user->TypeGet()));
+                break;
+#endif // FEATURE_SIMD
+
             case GT_STOREIND:
 #ifdef FEATURE_SIMD
-                if (user->TypeIs(TYP_SIMD8))
+                if (varTypeIsSIMD(user))
                 {
                     user->ChangeType(returnType);
                     break;
@@ -3319,7 +3359,6 @@ void Lowering::LowerCallStruct(GenTreeCall* call)
                 unreached();
         }
     }
-#endif // !TARGET_ARMARCH
 }
 
 //----------------------------------------------------------------------------------------------
@@ -3338,9 +3377,8 @@ void Lowering::LowerStoreCallStruct(GenTreeBlk* store)
     assert(store->Data()->IsCall());
     GenTreeCall* call = store->Data()->AsCall();
 
-    const ClassLayout* layout = store->GetLayout();
-    assert(layout->GetSlotCount() == 1);
-    const var_types regType = layout->GetRegisterType();
+    const ClassLayout* layout  = store->GetLayout();
+    const var_types    regType = layout->GetRegisterType();
 
     unsigned storeSize = store->GetLayout()->GetSize();
     if (regType != TYP_UNDEF)

src/coreclr/src/jit/morph.cpp

@@ -10191,8 +10191,19 @@ GenTree* Compiler::fgMorphBlockOperand(GenTree* tree, var_types asgType, unsigne
         }
         else if (effectiveVal->TypeGet() != asgType)
         {
-            GenTree* addr = gtNewOperNode(GT_ADDR, TYP_BYREF, effectiveVal);
-            effectiveVal  = gtNewIndir(asgType, addr);
+            if (effectiveVal->IsCall())
+            {
+#ifdef DEBUG
+                GenTreeCall* call = effectiveVal->AsCall();
+                assert(call->TypeGet() == TYP_STRUCT);
+                assert(blockWidth == info.compCompHnd->getClassSize(call->gtRetClsHnd));
+#endif
+            }
+            else
+            {
+                GenTree* addr = gtNewOperNode(GT_ADDR, TYP_BYREF, effectiveVal);
+                effectiveVal  = gtNewIndir(asgType, addr);
+            }
         }
     }
     else
@@ -11941,7 +11952,7 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
 
                 return tree;
             }
-            if (tree->TypeIs(TYP_STRUCT) && op1->OperIs(GT_OBJ, GT_BLK))
+            if (varTypeIsStruct(tree) && op1->OperIs(GT_OBJ, GT_BLK))
             {
                 assert(!compDoOldStructRetyping());
                 GenTree* addr = op1->AsBlk()->Addr();