[Arm64] Unused HFA arguments still get written to stack #35631
Description
For example, in System.Collections.Immutable.dll, Requires:NotNullAllowStructs(Vector1,String)`:
;* V00 arg0 [V00 ] ( 0, 0 ) simd16 -> zero-ref HFA(simd16) do-not-enreg[XS] addr-exposed
;* V01 arg1 [V01 ] ( 0, 0 ) ref -> zero-ref class-hnd
;
; Lcl frame size = 16
G_M20125_IG01:
A9BE7BFD stp fp, lr, [sp,#-32]!
910003FD mov fp, sp
3D8007A0 str q0, [fp,#16] ; *** Unused
G_M20125_IG02:
A8C27BFD ldp fp, lr, [sp],#32
D65F03C0 ret lrHere, HFA argument in q0 is still written to the stack, despite being unused.
category:cq
theme:register-allocator
skill-level:intermediate
cost:medium