JIT: Last-use copy elision does not handle IR created by physical promotion #87471
Description
For example:
fgMorphTree BB13, STMT00013 (before)
[000129] DACXG------ ▌ STORE_LCL_VAR int V06 tmp1
[000037] -ACXG------ └──▌ CALL int System.Comparison`1[System.Collections.BigStruct]:Invoke(System.Collections.BigStruct,System.Collections.BigStruct):int:this
[000006] ----------- this ├──▌ LCL_VAR ref V01 arg1 (last use)
[000207] -A--------- arg1 ├──▌ COMMA struct
[000206] UA--------- │ ├──▌ STORE_LCL_FLD int V07 tmp2 [+12]
[000205] ----------- │ │ └──▌ LCL_VAR int V17 tmp12
[000107] ----------- │ └──▌ LCL_VAR struct<System.Collections.BigStruct, 32> V07 tmp2 (last use)
[000210] -A--------- arg2 └──▌ COMMA struct
[000209] UA--------- ├──▌ STORE_LCL_FLD int V08 tmp3 [+12]
[000208] ----------- │ └──▌ LCL_VAR int V18 tmp13
[000109] ----------- └──▌ LCL_VAR struct<System.Collections.BigStruct, 32> V08 tmp3 (last use)
Initializing arg info for 37.CALL:
Args for call [000037] CALL after AddFinalArgsAndDetermineABIInfo:
CallArg[[000006].LCL_VAR ref (By value), 1 reg: rcx, byteAlignment=8, wellKnown[ThisPointer]]
CallArg[[000207].COMMA struct (By ref), 1 reg: rdx, byteAlignment=8, isStruct]
CallArg[[000210].COMMA struct (By ref), 1 reg: r8, byteAlignment=8, isStruct]
Morphing args for 37.CALL:
making an outgoing copy for struct argWe should set things up such that we do not need to make these copies. Either we can do the writeback stores before the call node or we can teach morph to support the pattern.