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//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
.intel_syntax noprefix
#include "unixasmmacros.inc"
#ifdef _DEBUG
// Version for when we're sure to be in the GC, checks whether or not the card
// needs to be updated
//
// void JIT_WriteBarrier_Debug(Object** dst, Object* src)
LEAF_ENTRY JIT_WriteBarrier_Debug, _TEXT
#ifdef WRITE_BARRIER_CHECK
// **ALSO update the shadow GC heap if that is enabled**
// Do not perform the work if g_GCShadow is 0
PREPARE_EXTERNAL_VAR g_GCShadow, rax
cmp qword ptr [rax], 0
je NoShadow
// If we end up outside of the heap don't corrupt random memory
mov r10, rdi
PREPARE_EXTERNAL_VAR g_lowest_address, r11
sub r10, [r11]
jb NoShadow
// Check that our adjusted destination is somewhere in the shadow gc
add r10, [rax]
PREPARE_EXTERNAL_VAR g_GCShadowEnd, r11
cmp r10, [r11]
ja NoShadow
// Write ref into real GC// see comment below about possibility of AV
mov [rdi], rsi
// Write ref into shadow GC
mov [r10], rsi
// Ensure that the write to the shadow heap occurs before the read from
// the GC heap so that race conditions are caught by INVALIDGCVALUE
mfence
// Check that GC/ShadowGC values match
mov r11, [rdi]
mov rax, [r10]
cmp rax, r11
je DoneShadow
mov r11, INVALIDGCVALUE
mov [r10], r11
jmp DoneShadow
// If we don't have a shadow GC we won't have done the write yet
NoShadow:
#endif
mov rax, rsi
// Do the move. It is correct to possibly take an AV here, the EH code
// figures out that this came from a WriteBarrier and correctly maps it back
// to the managed method which called the WriteBarrier (see setup in
// InitializeExceptionHandling, vm\exceptionhandling.cpp).
mov [rdi], rax
#ifdef WRITE_BARRIER_CHECK
// If we had a shadow GC then we already wrote to the real GC at the same time
// as the shadow GC so we want to jump over the real write immediately above
DoneShadow:
#endif
// See if we can just quick out
PREPARE_EXTERNAL_VAR g_ephemeral_low, r10
cmp rax, [r10]
jb Exit_Debug
PREPARE_EXTERNAL_VAR g_ephemeral_high, r10
cmp rax, [r10]
jnb Exit_Debug
// Check if we need to update the card table
// Calc pCardByte
shr rdi, 0Bh
PREPARE_EXTERNAL_VAR g_card_table, r10
add rdi, [r10]
// Check if this card is dirty
cmp byte ptr [rdi], 0FFh
jne UpdateCardTable_Debug
REPRET
UpdateCardTable_Debug:
mov byte ptr [rdi], 0FFh
ret
.balign 16
Exit_Debug:
REPRET
LEAF_END_MARKED JIT_WriteBarrier_Debug, _TEXT
#endif
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