Fix struct ReturnKind on SysV AMD64.

src/coreclr/jit/gcencode.cpp

@@ -21,6 +21,8 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 #include "gcinfotypes.h"
 #include "patchpointinfo.h"
 
+#ifdef JIT32_GCENCODER
+
 ReturnKind VarTypeToReturnKind(var_types type)
 {
     switch (type)
@@ -29,40 +31,38 @@ ReturnKind VarTypeToReturnKind(var_types type)
             return RT_Object;
         case TYP_BYREF:
             return RT_ByRef;
-#ifdef TARGET_X86
         case TYP_FLOAT:
         case TYP_DOUBLE:
             return RT_Float;
-#endif // TARGET_X86
         default:
             return RT_Scalar;
     }
 }
 
 ReturnKind GCInfo::getReturnKind()
 {
-    // Note the GCInfo representation only supports structs with up to 2 GC pointers.
+    // Note the JIT32 GCInfo representation only supports structs with 1 pointer.
     ReturnTypeDesc retTypeDesc = compiler->compRetTypeDesc;
     const unsigned regCount    = retTypeDesc.GetReturnRegCount();
 
-    switch (regCount)
+    if (regCount == 1)
+    {
+        return VarTypeToReturnKind(retTypeDesc.GetReturnRegType(0));
+    }
+    else
     {
-        case 1:
-            return VarTypeToReturnKind(retTypeDesc.GetReturnRegType(0));
-        case 2:
-            return GetStructReturnKind(VarTypeToReturnKind(retTypeDesc.GetReturnRegType(0)),
-                                       VarTypeToReturnKind(retTypeDesc.GetReturnRegType(1)));
-        default:
 #ifdef DEBUG
-            for (unsigned i = 0; i < regCount; i++)
-            {
-                assert(!varTypeIsGC(retTypeDesc.GetReturnRegType(i)));
-            }
+        for (unsigned i = 0; i < regCount; i++)
+        {
+            assert(!varTypeIsGC(retTypeDesc.GetReturnRegType(i)));
+        }
 #endif // DEBUG
-            return RT_Scalar;
+        return RT_Scalar;
     }
 }
 
+#endif // JIT32_GCENCODER
+
 // gcMarkFilterVarsPinned - Walk all lifetimes and make it so that anything
 //     live in a filter is marked as pinned (often by splitting the lifetime
 //     so that *only* the filter region is pinned).  This should only be

src/coreclr/jit/jitgcinfo.h

@@ -365,6 +365,8 @@ class GCInfo
 
 private:
     static size_t gcRecordEpilog(void* pCallBackData, unsigned offset);
+
+    ReturnKind getReturnKind();
 #else // JIT32_GCENCODER
     void gcInfoBlockHdrSave(GcInfoEncoder* gcInfoEncoder, unsigned methodSize, unsigned prologSize);
 
@@ -398,9 +400,6 @@ class GCInfo
 public:
     // This method updates the appropriate reg masks when a variable is moved.
     void gcUpdateForRegVarMove(regMaskTP srcMask, regMaskTP dstMask, LclVarDsc* varDsc);
-
-private:
-    ReturnKind getReturnKind();
 };
 
 inline unsigned char encodeUnsigned(BYTE* dest, unsigned value)

src/coreclr/vm/method.cpp

@@ -1299,6 +1299,15 @@ ReturnKind MethodDesc::ParseReturnKindFromSig(INDEBUG(bool supportStringConstruc
                                     regKinds[i] = RT_Scalar;
                                 }
                             }
+
+                            if (eeClass->GetEightByteClassification(0) == SystemVClassificationTypeSSE)
+                            {
+                                // Skip over SSE types since they do not consume integer registers.
+                                // An obj/byref in the 2nd eight bytes will be in the first integer register.
+                                regKinds[0] = regKinds[1];
+                                regKinds[1] = RT_Scalar;
+                            }
+
                             ReturnKind structReturnKind = GetStructReturnKind(regKinds[0], regKinds[1]);
                             return structReturnKind;
                         }