Backout promotion of structs containing fields of struct of single field.

Commit migrated from https://github.com/dotnet/coreclr/commit/a3c4de10600c10dc7df786fbb9b346bc786ae8f0

diff --git a/src/coreclr/src/jit/lclvars.cpp b/src/coreclr/src/jit/lclvars.cpp
index 61cf8a1..2c2637c 100644 (file)
--- a/src/coreclr/src/jit/lclvars.cpp
+++ b/src/coreclr/src/jit/lclvars.cpp
@@ -1543,60 +1543,8 @@ void Compiler::lvaCanPromoteStructType(CORINFO_CLASS_HANDLE    typeHnd,
 
             if (pFieldInfo->fldSize == 0)
             {
-                // Size of TYP_BLK, TYP_FUNC, TYP_VOID and TYP_STRUCT is zero.
-                // Early out if field type is other than TYP_STRUCT.
-                // This is a defensive check as we don't expect a struct to have
-                // fields of TYP_BLK, TYP_FUNC or TYP_VOID.
-                if (pFieldInfo->fldType != TYP_STRUCT)
-                {
-                    return;
-                }
-
                 // Non-primitive struct field.
-                // Try to promote structs of single field of scalar types aligned at their
-                // natural boundary.
-
-                // Do Not promote if the struct field in turn has more than one field.
-                if (info.compCompHnd->getClassNumInstanceFields(pFieldInfo->fldTypeHnd) != 1)
-                {
-                    return;
-                }
-
-                // Do not promote if the single field is not aligned at its natural boundary within
-                // the struct field.
-                CORINFO_FIELD_HANDLE fHnd    = info.compCompHnd->getFieldInClass(pFieldInfo->fldTypeHnd, 0);
-                unsigned             fOffset = info.compCompHnd->getFieldOffset(fHnd);
-                if (fOffset != 0)
-                {
-                    return;
-                }
-
-                CORINFO_CLASS_HANDLE cHnd;
-                CorInfoType          fieldCorType = info.compCompHnd->getFieldType(fHnd, &cHnd);
-                var_types            fieldVarType = JITtype2varType(fieldCorType);
-                unsigned             fieldSize    = genTypeSize(fieldVarType);
-
-                // Do not promote if either not a primitive type or size equal to ptr size on
-                // target or a struct containing a single floating-point field.
-                //
-                // TODO-PERF: Structs containing a single floating-point field on Amd64
-                // needs to be passed in integer registers. Right now LSRA doesn't support
-                // passing of floating-point LCL_VARS in integer registers.  Enabling promotion
-                // of such structs results in an assert in lsra right now.
-                //
-                // TODO-PERF: Right now promotion is confined to struct containing a ptr sized
-                // field (int/uint/ref/byref on 32-bits and long/ulong/ref/byref on 64-bits).
-                // Though this would serve the purpose of promoting Span<T> containing ByReference<T>,
-                // this can be extended to other primitive types as long as they are aligned at their
-                // natural boundary.
-                if (fieldSize == 0 || fieldSize != TARGET_POINTER_SIZE || varTypeIsFloating(fieldVarType))
-                {
-                    return;
-                }
-
-                // Retype the field as the type of the single field of the struct
-                pFieldInfo->fldType = fieldVarType;
-                pFieldInfo->fldSize = fieldSize;
+                return;
             }
 
             if ((pFieldInfo->fldOffset % pFieldInfo->fldSize) != 0)

diff --git a/src/coreclr/src/jit/lower.cpp b/src/coreclr/src/jit/lower.cpp
index 3c685f6..b3a674e 100644 (file)
--- a/src/coreclr/src/jit/lower.cpp
+++ b/src/coreclr/src/jit/lower.cpp
@@ -971,42 +971,6 @@ GenTreePtr Lowering::NewPutArg(GenTreeCall* call, GenTreePtr arg, fgArgTabEntryP
                 assert(!varTypeIsSIMD(arg));
                 numRefs = comp->info.compCompHnd->getClassGClayout(arg->gtObj.gtClass, gcLayout);
                 putArg->AsPutArgStk()->setGcPointers(numRefs, gcLayout);
-
-#ifdef _TARGET_X86_
-                // On x86 VM lies about the type of a struct containing a pointer sized
-                // integer field by returning the type of its field as the type of struct.
-                // Such struct can be passed in a register depending its position in
-                // parameter list.  VM does this unwrapping only one level and therefore
-                // a type like Struct Foo { Struct Bar { int f}} awlays needs to be
-                // passed on stack.  Also, VM doesn't lie about type of such a struct
-                // when it is a field of another struct.  That is VM doesn't lie about
-                // the type of Foo.Bar
-                //
-                // Promotion of structs containing structs of single field can promote
-                // such a struct.  Say Foo.Bar field is getting passed as a parameter
-                // to a call, Since it is a TYP_STRUCT, as per x86 ABI it should always
-                // be passed on stack.  Therefore GenTree node under a PUTARG_STK could
-                // be GT_OBJ(GT_LCL_VAR_ADDR(v1)), where local v1 could be a promoted
-                // field standing for Foo.Bar.  Note that the type of v1 will be the
-                // type of field of Foo.Bar.f when Foo is promoted.  That is v1
-                // will be a scalar type.  In this case we need to pass v1 on stack
-                // instead of in a register.
-                //
-                // TODO-PERF: replace GT_OBJ(GT_LCL_VAR_ADDR(v1)) with v1 if v1 is
-                // a scalar type and the width of GT_OBJ matches the type size of v1.
-                // Note that this cannot be done till call node arguments are morphed
-                // because we should not lose the fact that the type of argument is
-                // a struct so that the arg gets correctly marked to be passed on stack.
-                GenTree* objOp1 = arg->gtGetOp1();
-                if (objOp1->OperGet() == GT_LCL_VAR_ADDR)
-                {
-                    unsigned lclNum = objOp1->AsLclVarCommon()->GetLclNum();
-                    if (comp->lvaTable[lclNum].lvType != TYP_STRUCT)
-                    {
-                        comp->lvaSetVarDoNotEnregister(lclNum DEBUGARG(Compiler::DNER_VMNeedsStackAddr));
-                    }
-                }
-#endif // _TARGET_X86_
             }
         }
 #endif // FEATURE_PUT_STRUCT_ARG_STK