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UniversalTransition.asm
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UniversalTransition.asm
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;; Licensed to the .NET Foundation under one or more agreements.
;; The .NET Foundation licenses this file to you under the MIT license.
#include "AsmMacros.h"
#ifdef _DEBUG
#define TRASH_SAVED_ARGUMENT_REGISTERS
#endif
#ifdef TRASH_SAVED_ARGUMENT_REGISTERS
EXTERN RhpIntegerTrashValues
EXTERN RhpFpTrashValues
#endif ;; TRASH_SAVED_ARGUMENT_REGISTERS
#define COUNT_ARG_REGISTERS (4)
#define INTEGER_REGISTER_SIZE (4)
#define ARGUMENT_REGISTERS_SIZE (COUNT_ARG_REGISTERS * INTEGER_REGISTER_SIZE)
;; Largest return block is 4 doubles
#define RETURN_BLOCK_SIZE (32)
#define COUNT_FLOAT_ARG_REGISTERS (8)
#define FLOAT_REGISTER_SIZE (8)
#define FLOAT_ARG_REGISTERS_SIZE (COUNT_FLOAT_ARG_REGISTERS * FLOAT_REGISTER_SIZE)
#define PUSHED_LR_SIZE (4)
#define PUSHED_R11_SIZE (4)
;;
;; From CallerSP to ChildSP, the stack frame is composed of the following adjacent regions:
;;
;; ARGUMENT_REGISTERS_SIZE
;; RETURN_BLOCK_SIZE
;; FLOAT_ARG_REGISTERS_SIZE
;; PUSHED_LR
;; PUSHED_R11
;;
#define DISTANCE_FROM_CHILDSP_TO_RETURN_BLOCK (PUSHED_R11_SIZE + PUSHED_LR_SIZE + FLOAT_ARG_REGISTERS_SIZE)
TEXTAREA
;;
;; RhpUniversalTransition
;;
;; At input to this function, r0-3, d0-7 and the stack may contain any number of arguments.
;;
;; In addition, there are 2 extra arguments passed in the RED ZONE (8 byte negative space
;; off of sp).
;; sp-4 will contain the managed function that is to be called by this transition function
;; sp-8 will contain the pointer sized extra argument to the managed function
;;
;; When invoking the callee:
;;
;; r0 shall contain a pointer to the TransitionBlock
;; r1 shall contain the value that was in sp-8 at entry to this function
;;
;; Frame layout is:
;;
;; {StackPassedArgs} ChildSP+078 CallerSP+000
;; {IntArgRegs (r0-r3) (0x10 bytes)} ChildSP+068 CallerSP-010
;; {ReturnBlock (0x20 bytes)} ChildSP+048 CallerSP-030
;; -- The base address of the Return block is the TransitionBlock pointer, the floating point args are
;; in the neg space of the TransitionBlock pointer. Note that the callee has knowledge of the exact
;; layout of all pieces of the frame that lie at or above the pushed floating point registers.
;; {FpArgRegs (d0-d7) (0x40 bytes)} ChildSP+008 CallerSP-070
;; {PushedLR} ChildSP+004 CallerSP-074
;; {PushedR11} ChildSP+000 CallerSP-078
;;
;; NOTE: If the frame layout ever changes, the C++ UniversalTransitionStackFrame structure
;; must be updated as well.
;;
;; NOTE: The callee receives a pointer to the base of the ReturnBlock, and the callee has
;; knowledge of the exact layout of all pieces of the frame that lie at or above the pushed
;; FpArgRegs.
;;
;; NOTE: The stack walker guarantees that conservative GC reporting will be applied to
;; everything between the base of the ReturnBlock and the top of the StackPassedArgs.
;;
MACRO
UNIVERSAL_TRANSITION $FunctionName
NESTED_ENTRY Rhp$FunctionName
;; Save argument registers (including floating point) and the return address.
;; NOTE: While we do that, capture the two arguments in the red zone into r12 and r3.
PROLOG_NOP ldr r12, [sp, #-4] ; Capture first argument from red zone into r12
PROLOG_PUSH {r3} ; Push r3
PROLOG_NOP ldr r3, [sp, #-4] ; Capture second argument from red zone into r3
PROLOG_PUSH {r0-r2} ; Push the rest of the registers
PROLOG_STACK_ALLOC RETURN_BLOCK_SIZE ; Save space a buffer to be used to hold return buffer data.
PROLOG_VPUSH {d0-d7} ; Capture the floating point argument registers
PROLOG_PUSH {r11,lr} ; Save caller's frame chain pointer and PC
;; Setup the arguments to the transition thunk.
mov r1, r3
#ifdef TRASH_SAVED_ARGUMENT_REGISTERS
;; Before calling out, trash all of the argument registers except the ones (r0, r1) that
;; hold outgoing arguments. All of these registers have been saved to the transition
;; frame, and the code at the call target is required to use only the transition frame
;; copies when dispatching this call to the eventual callee.
ldr r3, =RhpFpTrashValues
vldr d0, [r3, #(0 * 8)]
vldr d1, [r3, #(1 * 8)]
vldr d2, [r3, #(2 * 8)]
vldr d3, [r3, #(3 * 8)]
vldr d4, [r3, #(4 * 8)]
vldr d5, [r3, #(5 * 8)]
vldr d6, [r3, #(6 * 8)]
vldr d7, [r3, #(7 * 8)]
ldr r3, =RhpIntegerTrashValues
ldr r2, [r3, #(2 * 4)]
ldr r3, [r3, #(3 * 4)]
#endif // TRASH_SAVED_ARGUMENT_REGISTERS
;; Make the ReturnFromUniversalTransition alternate entry 4 byte aligned
ALIGN 4
add r0, sp, #DISTANCE_FROM_CHILDSP_TO_RETURN_BLOCK ;; First parameter to target function is a pointer to the return block
blx r12
EXPORT_POINTER_TO_ADDRESS PointerToReturnFrom$FunctionName
; We cannot make the label public as that tricks DIA stackwalker into thinking
; it's the beginning of a method. For this reason we export an auxiliary variable
; holding the address instead.
;; Move the result (the target address) to r12 so it doesn't get overridden when we restore the
;; argument registers. Additionally make sure the thumb2 bit is set.
orr r12, r0, #1
;; Restore caller's frame chain pointer and PC.
EPILOG_POP {r11,lr}
;; Restore the argument registers.
EPILOG_VPOP {d0-d7}
EPILOG_STACK_FREE RETURN_BLOCK_SIZE ; pop return block conservatively reported area
EPILOG_POP {r0-r3}
;; Tailcall to the target address.
EPILOG_BRANCH_REG r12
NESTED_END Rhp$FunctionName
MEND
; To enable proper step-in behavior in the debugger, we need to have two instances
; of the thunk. For the first one, the debugger steps into the call in the function,
; for the other, it steps over it.
UNIVERSAL_TRANSITION UniversalTransition
UNIVERSAL_TRANSITION UniversalTransition_DebugStepTailCall
END