[RISC-V][LoongArch64] New passing info for floating-point structs (#103945)

* Replace StructFloatFieldInfoFlags with FpStructInRegistersInfo which carries also exact field sizes and offsets

* Replace StructFloatFieldInfoFlags with FpStruct::Flags in profiler

* Remove FpStructInRegistersInfo::FromOldFlags()

* Fix duplicating types in HandleInlineArray

* Remove signedness from FpStruct::IntKind because most probably we won't need it

* Remove old StructFloatFieldInfoFlags calculating routine

* Typo in TARGET_LOONGARCH64

* Remove m_returnedFpFieldOffsets from ArgIterator

* Add missing ENREGISTERED_PARAMTYPE_MAXSIZE condition to C# version of FpStruct info calculation

* Rename RISCV64PassStructInRegister to match settled casing for RiscV in class names

* Update hardcoded flags for float and double in ArgIteratorTemplate::ComputeReturnFlags()

This fixes JIT/HardwareIntrinsics/General/Vector* tests.

* Fix build on other platforms

* Update LoongArch to use FpStructInRegistersInfo

* Remove unused old flag masks

* LoongArch64 typo

Co-authored-by: Qiao Pengcheng <qiaopengcheng@loongson.cn>

* Missing FpStruct namespace

Co-authored-by: Qiao Pengcheng <qiaopengcheng@loongson.cn>

* Missing FpStruct namespace

Co-authored-by: Qiao Pengcheng <qiaopengcheng@loongson.cn>

* Missing FpStruct namespace

Co-authored-by: Qiao Pengcheng <qiaopengcheng@loongson.cn>

* Use FpStruct namespace everywhere in JIT

* JIT review

* Update StructFloatFieldInfoFlags description

* Revert to hitherto instruction set order as it's not the point of this PR

* Unify get{LoongArch,RiscV}64PassFpStructInRegistersInfo JIT interfaces

* Use JIT_TO_EE_TRANSITION instead of _LEAF because MethodTable::GetFpStructInRegistersInfo may throw

* Remove FpStruct::IntKind, we should have similar info in ClassLayout in JIT

* Change JIT interface to return a struct similar to CORINFO_SWIFT_LOWERING to facilitate code unification in the future

* Change JIT to use new Swift-like getFpStructLowering

* Cache CORINFO_FPSTRUCT_LOWERING

* Update LoongArch classifier to use CORINFO_FPSTRUCT_LOWERING

* Update StructFloatInfoFlags doc comment on C#

* Move StructFloatFieldInfoFlags and FpStructInRegistersInfo out of the JIT interface

* Merge LoongArch and RISC-V AOT calculation of FpStructInRegistersInfo because they were identical. Move it to Common\Internal/Runtime because it's no longer exposed in JIT interface.

* Don't zero-initialize CORINFO_FPSTRUCT_LOWERING

* Add note for CORINFO_FPSTRUCT_LOWERING::loweredElements type

---------

Co-authored-by: Qiao Pengcheng <qiaopengcheng@loongson.cn>

Author: 2 people

src/coreclr/inc/corinfo.h

@@ -307,45 +307,6 @@ struct SYSTEMV_AMD64_CORINFO_STRUCT_REG_PASSING_DESCRIPTOR
     }
 };
 
-// StructFloadFieldInfoFlags: used on LoongArch64 architecture by `getLoongArch64PassStructInRegisterFlags` and
-// `getRISCV64PassStructInRegisterFlags` API to convey struct argument passing information.
-//
-// `STRUCT_NO_FLOAT_FIELD` means structs are not passed using the float register(s).
-//
-// Otherwise, and only for structs with no more than two fields and a total struct size no larger
-// than two pointers:
-//
-// The lowest four bits denote the floating-point info:
-//   bit 0: `1` means there is only one float or double field within the struct.
-//   bit 1: `1` means only the first field is floating-point type.
-//   bit 2: `1` means only the second field is floating-point type.
-//   bit 3: `1` means the two fields are both floating-point type.
-// The bits[5:4] denoting whether the field size is 8-bytes:
-//   bit 4: `1` means the first field's size is 8.
-//   bit 5: `1` means the second field's size is 8.
-//
-// Note that bit 0 and 3 cannot both be set.
-enum StructFloatFieldInfoFlags
-{
-    STRUCT_NO_FLOAT_FIELD         = 0x0,
-    STRUCT_FLOAT_FIELD_ONLY_ONE   = 0x1,
-    STRUCT_FLOAT_FIELD_ONLY_TWO   = 0x8,
-    STRUCT_FLOAT_FIELD_FIRST      = 0x2,
-    STRUCT_FLOAT_FIELD_SECOND     = 0x4,
-    STRUCT_FIRST_FIELD_SIZE_IS8   = 0x10,
-    STRUCT_SECOND_FIELD_SIZE_IS8  = 0x20,
-
-    STRUCT_FIRST_FIELD_DOUBLE     = (STRUCT_FLOAT_FIELD_FIRST | STRUCT_FIRST_FIELD_SIZE_IS8),
-    STRUCT_SECOND_FIELD_DOUBLE    = (STRUCT_FLOAT_FIELD_SECOND | STRUCT_SECOND_FIELD_SIZE_IS8),
-    STRUCT_FIELD_TWO_DOUBLES      = (STRUCT_FIRST_FIELD_SIZE_IS8 | STRUCT_SECOND_FIELD_SIZE_IS8 | STRUCT_FLOAT_FIELD_ONLY_TWO),
-
-    STRUCT_MERGE_FIRST_SECOND     = (STRUCT_FLOAT_FIELD_FIRST | STRUCT_FLOAT_FIELD_ONLY_TWO),
-    STRUCT_MERGE_FIRST_SECOND_8   = (STRUCT_FLOAT_FIELD_FIRST | STRUCT_FLOAT_FIELD_ONLY_TWO | STRUCT_SECOND_FIELD_SIZE_IS8),
-
-    STRUCT_HAS_FLOAT_FIELDS_MASK  = (STRUCT_FLOAT_FIELD_FIRST | STRUCT_FLOAT_FIELD_SECOND | STRUCT_FLOAT_FIELD_ONLY_TWO | STRUCT_FLOAT_FIELD_ONLY_ONE),
-    STRUCT_HAS_8BYTES_FIELDS_MASK = (STRUCT_FIRST_FIELD_SIZE_IS8 | STRUCT_SECOND_FIELD_SIZE_IS8),
-};
-
 #include "corinfoinstructionset.h"
 
 // CorInfoHelpFunc defines the set of helpers (accessed via the ICorDynamicInfo::getHelperFtn())
@@ -1940,6 +1901,23 @@ struct CORINFO_SWIFT_LOWERING
     size_t numLoweredElements;
 };
 
+#define MAX_FPSTRUCT_LOWERED_ELEMENTS 2
+
+// Lowering information on fields of a struct passed by hardware floating-point calling convention on RISC-V and LoongArch
+struct CORINFO_FPSTRUCT_LOWERING
+{
+    // Whether the struct should be passed by integer calling convention (cannot be passed by FP calling convention).
+    bool byIntegerCallConv;
+    // Types of lowered struct fields.
+    // Note: the integer field is denoted with a signed type reflecting size only so e.g. ushort is reported
+    // as CORINFO_TYPE_SHORT and object or string is reported as CORINFO_TYPE_LONG.
+    CorInfoType loweredElements[MAX_FPSTRUCT_LOWERED_ELEMENTS];
+    // Offsets of lowered struct fields.
+    uint32_t offsets[MAX_FPSTRUCT_LOWERED_ELEMENTS];
+    // Number of lowered struct fields.
+    size_t numLoweredElements;
+};
+
 #define SIZEOF__CORINFO_Object                            TARGET_POINTER_SIZE /* methTable */
 
 #define CORINFO_Array_MaxLength                           0x7FFFFFC7
@@ -3065,8 +3043,9 @@ class ICorStaticInfo
     // Classifies a swift structure into primitives or an implicit byref for ABI purposes.
     virtual void getSwiftLowering(CORINFO_CLASS_HANDLE structHnd, CORINFO_SWIFT_LOWERING* pLowering) = 0;
 
-    virtual uint32_t getLoongArch64PassStructInRegisterFlags(CORINFO_CLASS_HANDLE cls) = 0;
-    virtual uint32_t getRISCV64PassStructInRegisterFlags(CORINFO_CLASS_HANDLE cls) = 0;
+    // Returns lowering info for fields of a RISC-V/LoongArch struct passed in registers according to
+    // hardware floating-point calling convention.
+    virtual void getFpStructLowering(CORINFO_CLASS_HANDLE structHnd, CORINFO_FPSTRUCT_LOWERING* pLowering) = 0;
 };
 
 /*****************************************************************************

src/coreclr/inc/icorjitinfoimpl_generated.h

@@ -520,11 +520,9 @@ void getSwiftLowering(
           CORINFO_CLASS_HANDLE structHnd,
           CORINFO_SWIFT_LOWERING* pLowering) override;
 
-uint32_t getLoongArch64PassStructInRegisterFlags(
-          CORINFO_CLASS_HANDLE structHnd) override;
-
-uint32_t getRISCV64PassStructInRegisterFlags(
-          CORINFO_CLASS_HANDLE structHnd) override;
+void getFpStructLowering(
+          CORINFO_CLASS_HANDLE structHnd,
+          CORINFO_FPSTRUCT_LOWERING* pLowering) override;
 
 uint32_t getThreadTLSIndex(
           void** ppIndirection) override;

src/coreclr/inc/jiteeversionguid.h

@@ -43,11 +43,11 @@ typedef const GUID *LPCGUID;
 #define GUID_DEFINED
 #endif // !GUID_DEFINED
 
-constexpr GUID JITEEVersionIdentifier = { /* 488a17ce-26c9-4ad0-a7b7-79bf320ea4d1 */
-    0x488a17ce,
-    0x26c9,
-    0x4ad0,
-    {0xa7, 0xb7, 0x79, 0xbf, 0x32, 0x0e, 0xa4, 0xd1}
+constexpr GUID JITEEVersionIdentifier = { /* e770e8ad-50d5-4511-a435-a3ed3a847a47 */
+    0xe770e8ad,
+    0x50d5,
+    0x4511,
+    {0xa4, 0x35, 0xa3, 0xed, 0x3a, 0x84, 0x7a, 0x47}
   };
 
 //////////////////////////////////////////////////////////////////////////////////////////////////////////

src/coreclr/jit/ICorJitInfo_names_generated.h

@@ -130,8 +130,7 @@ DEF_CLR_API(getMethodNameFromMetadata)
 DEF_CLR_API(getMethodHash)
 DEF_CLR_API(getSystemVAmd64PassStructInRegisterDescriptor)
 DEF_CLR_API(getSwiftLowering)
-DEF_CLR_API(getLoongArch64PassStructInRegisterFlags)
-DEF_CLR_API(getRISCV64PassStructInRegisterFlags)
+DEF_CLR_API(getFpStructLowering)
 DEF_CLR_API(getThreadTLSIndex)
 DEF_CLR_API(getAddrOfCaptureThreadGlobal)
 DEF_CLR_API(getHelperFtn)

src/coreclr/jit/ICorJitInfo_wrapper_generated.hpp

@@ -1238,22 +1238,13 @@ void WrapICorJitInfo::getSwiftLowering(
     API_LEAVE(getSwiftLowering);
 }
 
-uint32_t WrapICorJitInfo::getLoongArch64PassStructInRegisterFlags(
-          CORINFO_CLASS_HANDLE structHnd)
-{
-    API_ENTER(getLoongArch64PassStructInRegisterFlags);
-    uint32_t temp = wrapHnd->getLoongArch64PassStructInRegisterFlags(structHnd);
-    API_LEAVE(getLoongArch64PassStructInRegisterFlags);
-    return temp;
-}
-
-uint32_t WrapICorJitInfo::getRISCV64PassStructInRegisterFlags(
-          CORINFO_CLASS_HANDLE structHnd)
+void WrapICorJitInfo::getFpStructLowering(
+          CORINFO_CLASS_HANDLE structHnd,
+          CORINFO_FPSTRUCT_LOWERING* pLowering)
 {
-    API_ENTER(getRISCV64PassStructInRegisterFlags);
-    uint32_t temp = wrapHnd->getRISCV64PassStructInRegisterFlags(structHnd);
-    API_LEAVE(getRISCV64PassStructInRegisterFlags);
-    return temp;
+    API_ENTER(getFpStructLowering);
+    wrapHnd->getFpStructLowering(structHnd, pLowering);
+    API_LEAVE(getFpStructLowering);
 }
 
 uint32_t WrapICorJitInfo::getThreadTLSIndex(

src/coreclr/jit/buildstring.cpp

@@ -1,17 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#define STRINGIFY(L)     #L
-#define MAKESTRING(M, L) M(L)
-#define STRINGIZE(X)     MAKESTRING(STRINGIFY, X)
+#include "utils.h"
 
 #if defined(__clang__)
 #define BUILD_COMPILER                                                                                                 \
-    "Clang " STRINGIZE(__clang_major__) "." STRINGIZE(__clang_minor__) "." STRINGIZE(__clang_patchlevel__)
+    "Clang " STRINGIFY(__clang_major__) "." STRINGIFY(__clang_minor__) "." STRINGIFY(__clang_patchlevel__)
 #elif defined(_MSC_VER)
-#define BUILD_COMPILER "MSVC " STRINGIZE(_MSC_FULL_VER)
+#define BUILD_COMPILER "MSVC " STRINGIFY(_MSC_FULL_VER)
 #elif defined(__GNUC__)
-#define BUILD_COMPILER "GCC " STRINGIZE(__GNUC__) "." STRINGIZE(__GNUC_MINOR__) "." STRINGIZE(__GNUC_PATCHLEVEL__)
+#define BUILD_COMPILER "GCC " STRINGIFY(__GNUC__) "." STRINGIFY(__GNUC_MINOR__) "." STRINGIFY(__GNUC_PATCHLEVEL__)
 #else
 #define BUILD_COMPILER "Unknown"
 #endif
@@ -26,6 +24,8 @@
 #define TARGET_ARCH_STRING "arm64"
 #elif defined(TARGET_LOONGARCH64)
 #define TARGET_ARCH_STRING "loongarch64"
+#elif defined(TARGET_RISCV64)
+#define TARGET_ARCH_STRING "riscv64"
 #else
 #define TARGET_ARCH_STRING "Unknown"
 #endif

src/coreclr/jit/compiler.cpp

@@ -927,37 +927,24 @@ var_types Compiler::getReturnTypeForStruct(CORINFO_CLASS_HANDLE     clsHnd,
         howToReturnStruct   = SPK_ByReference;
         useType             = TYP_UNKNOWN;
     }
-#elif defined(TARGET_LOONGARCH64)
+#elif defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
     if (structSize <= (TARGET_POINTER_SIZE * 2))
     {
-        uint32_t floatFieldFlags = info.compCompHnd->getLoongArch64PassStructInRegisterFlags(clsHnd);
-
-        if ((floatFieldFlags & STRUCT_FLOAT_FIELD_ONLY_ONE) != 0)
-        {
-            howToReturnStruct = SPK_PrimitiveType;
-            useType           = (structSize > 4) ? TYP_DOUBLE : TYP_FLOAT;
-        }
-        else if (floatFieldFlags & (STRUCT_HAS_FLOAT_FIELDS_MASK ^ STRUCT_FLOAT_FIELD_ONLY_ONE))
-        {
-            howToReturnStruct = SPK_ByValue;
-            useType           = TYP_STRUCT;
-        }
-    }
-
-#elif defined(TARGET_RISCV64)
-    if (structSize <= (TARGET_POINTER_SIZE * 2))
-    {
-        uint32_t floatFieldFlags = info.compCompHnd->getRISCV64PassStructInRegisterFlags(clsHnd);
-
-        if ((floatFieldFlags & STRUCT_FLOAT_FIELD_ONLY_ONE) != 0)
-        {
-            howToReturnStruct = SPK_PrimitiveType;
-            useType           = (structSize > 4) ? TYP_DOUBLE : TYP_FLOAT;
-        }
-        else if (floatFieldFlags & (STRUCT_HAS_FLOAT_FIELDS_MASK ^ STRUCT_FLOAT_FIELD_ONLY_ONE))
+        const CORINFO_FPSTRUCT_LOWERING* lowering = GetFpStructLowering(clsHnd);
+        if (!lowering->byIntegerCallConv)
         {
-            howToReturnStruct = SPK_ByValue;
-            useType           = TYP_STRUCT;
+            if (lowering->numLoweredElements == 1)
+            {
+                useType = JITtype2varType(lowering->loweredElements[0]);
+                assert(varTypeIsFloating(useType));
+                howToReturnStruct = SPK_PrimitiveType;
+            }
+            else
+            {
+                assert(lowering->numLoweredElements == 2);
+                howToReturnStruct = SPK_ByValue;
+                useType           = TYP_STRUCT;
+            }
         }
     }
 
@@ -1998,6 +1985,9 @@ void Compiler::compInit(ArenaAllocator*       pAlloc,
 #ifdef SWIFT_SUPPORT
     m_swiftLoweringCache = nullptr;
 #endif
+#if defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
+    m_fpStructLoweringCache = nullptr;
+#endif
 
     // check that HelperCallProperties are initialized
 
@@ -8301,6 +8291,53 @@ void Compiler::GetStructTypeOffset(
     GetStructTypeOffset(structDesc, type0, type1, offset0, offset1);
 }
 
+#elif defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
+//------------------------------------------------------------------------
+// GetFpStructLowering: Gets the information on passing of a struct according to hardware floating-point
+// calling convention, i.e. the types and offsets of struct fields lowered for passing.
+//
+// Arguments:
+//      structHandle - type handle
+//
+// Return value:
+//      Lowering info for the struct fields
+const CORINFO_FPSTRUCT_LOWERING* Compiler::GetFpStructLowering(CORINFO_CLASS_HANDLE structHandle)
+{
+    if (m_fpStructLoweringCache == nullptr)
+        m_fpStructLoweringCache = new (this, CMK_CallArgs) FpStructLoweringMap(getAllocator(CMK_CallArgs));
+
+    CORINFO_FPSTRUCT_LOWERING* lowering;
+    if (!m_fpStructLoweringCache->Lookup(structHandle, &lowering))
+    {
+        lowering = new (this, CMK_CallArgs) CORINFO_FPSTRUCT_LOWERING;
+        info.compCompHnd->getFpStructLowering(structHandle, lowering);
+        m_fpStructLoweringCache->Set(structHandle, lowering);
+#ifdef DEBUG
+        if (verbose)
+        {
+            printf("**** getFpStructInRegistersInfo(0x%x (%s, %u bytes)) =>\n", dspPtr(structHandle),
+                   eeGetClassName(structHandle), info.compCompHnd->getClassSize(structHandle));
+
+            if (lowering->byIntegerCallConv)
+            {
+                printf("        pass by integer calling convention\n");
+            }
+            else
+            {
+                printf("        may be passed by floating-point calling convention (%zu fields):\n",
+                       lowering->numLoweredElements);
+                for (size_t i = 0; i < lowering->numLoweredElements; ++i)
+                {
+                    const char* type = varTypeName(JITtype2varType(lowering->loweredElements[i]));
+                    printf("         * field[%zu]: type %s at offset %u\n", i, type, lowering->offsets[i]);
+                }
+            }
+        }
+#endif // DEBUG
+    }
+    return lowering;
+}
+
 #endif // defined(UNIX_AMD64_ABI)
 
 /*****************************************************************************/

src/coreclr/jit/compiler.h

@@ -561,17 +561,9 @@ class LclVarDsc
     unsigned char lvIsLastUseCopyOmissionCandidate : 1;
 #endif // FEATURE_IMPLICIT_BYREFS
 
-#if defined(TARGET_LOONGARCH64)
-    unsigned char lvIs4Field1 : 1; // Set if the 1st field is int or float within struct for LA-ABI64.
-    unsigned char lvIs4Field2 : 1; // Set if the 2nd field is int or float within struct for LA-ABI64.
-    unsigned char lvIsSplit   : 1; // Set if the argument is splited.
-#endif                             // defined(TARGET_LOONGARCH64)
-
-#if defined(TARGET_RISCV64)
-    unsigned char lvIs4Field1 : 1; // Set if the 1st field is int or float within struct for RISCV64.
-    unsigned char lvIs4Field2 : 1; // Set if the 2nd field is int or float within struct for RISCV64.
-    unsigned char lvIsSplit   : 1; // Set if the argument is splited.
-#endif                             // defined(TARGET_RISCV64)
+#if defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
+    unsigned char lvIsSplit : 1; // Set if the argument is split across last integer register and stack.
+#endif                           // defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
 
     unsigned char lvSingleDef : 1; // variable has a single def. Used to identify ref type locals that can get type
                                    // updates
@@ -11496,6 +11488,11 @@ class Compiler
     void GetStructTypeOffset(
         CORINFO_CLASS_HANDLE typeHnd, var_types* type0, var_types* type1, uint8_t* offset0, uint8_t* offset1);
 
+#elif defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
+    typedef JitHashTable<CORINFO_CLASS_HANDLE, JitPtrKeyFuncs<struct CORINFO_CLASS_STRUCT_>, CORINFO_FPSTRUCT_LOWERING*>
+                                     FpStructLoweringMap;
+    FpStructLoweringMap*             m_fpStructLoweringCache;
+    const CORINFO_FPSTRUCT_LOWERING* GetFpStructLowering(CORINFO_CLASS_HANDLE structHandle);
 #endif // defined(UNIX_AMD64_ABI)
 
     void     fgMorphMultiregStructArgs(GenTreeCall* call);

src/coreclr/jit/gentree.cpp

@@ -29544,37 +29544,29 @@ void ReturnTypeDesc::InitializeStructReturnType(Compiler*                comp,
 
 #elif defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV64)
             assert((structSize >= TARGET_POINTER_SIZE) && (structSize <= (2 * TARGET_POINTER_SIZE)));
-
-#ifdef TARGET_LOONGARCH64
-            uint32_t floatFieldFlags = comp->info.compCompHnd->getLoongArch64PassStructInRegisterFlags(retClsHnd);
-#else
-            uint32_t floatFieldFlags = comp->info.compCompHnd->getRISCV64PassStructInRegisterFlags(retClsHnd);
-#endif
             BYTE gcPtrs[2] = {TYPE_GC_NONE, TYPE_GC_NONE};
             comp->info.compCompHnd->getClassGClayout(retClsHnd, &gcPtrs[0]);
-
-            if (floatFieldFlags & STRUCT_FLOAT_FIELD_ONLY_TWO)
-            {
-                comp->compFloatingPointUsed = true;
-                assert((structSize > 8) == ((floatFieldFlags & STRUCT_HAS_8BYTES_FIELDS_MASK) > 0));
-                m_regType[0] = (floatFieldFlags & STRUCT_FIRST_FIELD_SIZE_IS8) ? TYP_DOUBLE : TYP_FLOAT;
-                m_regType[1] = (floatFieldFlags & STRUCT_SECOND_FIELD_SIZE_IS8) ? TYP_DOUBLE : TYP_FLOAT;
-            }
-            else if (floatFieldFlags & STRUCT_FLOAT_FIELD_FIRST)
-            {
-                comp->compFloatingPointUsed = true;
-                assert((structSize > 8) == ((floatFieldFlags & STRUCT_HAS_8BYTES_FIELDS_MASK) > 0));
-                m_regType[0] = (floatFieldFlags & STRUCT_FIRST_FIELD_SIZE_IS8) ? TYP_DOUBLE : TYP_FLOAT;
-                m_regType[1] =
-                    (floatFieldFlags & STRUCT_SECOND_FIELD_SIZE_IS8) ? comp->getJitGCType(gcPtrs[1]) : TYP_INT;
-            }
-            else if (floatFieldFlags & STRUCT_FLOAT_FIELD_SECOND)
+            const CORINFO_FPSTRUCT_LOWERING* lowering = comp->GetFpStructLowering(retClsHnd);
+            if (!lowering->byIntegerCallConv)
             {
                 comp->compFloatingPointUsed = true;
-                assert((structSize > 8) == ((floatFieldFlags & STRUCT_HAS_8BYTES_FIELDS_MASK) > 0));
-                m_regType[0] =
-                    (floatFieldFlags & STRUCT_FIRST_FIELD_SIZE_IS8) ? comp->getJitGCType(gcPtrs[0]) : TYP_INT;
-                m_regType[1] = (floatFieldFlags & STRUCT_SECOND_FIELD_SIZE_IS8) ? TYP_DOUBLE : TYP_FLOAT;
+                assert(lowering->numLoweredElements == MAX_RET_REG_COUNT);
+                var_types types[MAX_RET_REG_COUNT] = {JITtype2varType(lowering->loweredElements[0]),
+                                                      JITtype2varType(lowering->loweredElements[1])};
+                assert(varTypeIsFloating(types[0]) || varTypeIsFloating(types[1]));
+                assert((structSize > 8) == ((genTypeSize(types[0]) == 8) || (genTypeSize(types[1]) == 8)));
+                for (unsigned i = 0; i < MAX_RET_REG_COUNT; ++i)
+                {
+                    if (varTypeIsFloating(types[i]))
+                    {
+                        m_regType[i] = types[i];
+                    }
+                    else
+                    {
+                        assert(varTypeIsIntegralOrI(types[i]));
+                        m_regType[i] = (genTypeSize(types[i]) == 8) ? comp->getJitGCType(gcPtrs[i]) : TYP_INT;
+                    }
+                }
             }
             else
             {

src/coreclr/jit/gentree.h

@@ -4544,7 +4544,7 @@ struct CallArgABIInformation
     SYSTEMV_AMD64_CORINFO_STRUCT_REG_PASSING_DESCRIPTOR StructDesc;
 #endif // UNIX_AMD64_ABI
 #if defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV64)
-    // For LoongArch64's ABI, the struct which has float field(s) and no more than two fields
+    // For LoongArch64's and RISC-V 64's ABI, the struct which has float field(s) and no more than two fields
     // may be passed by float register(s).
     // e.g  `struct {int a; float b;}` passed by an integer register and a float register.
     var_types StructFloatFieldType[2];