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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Push all callee-saved registers to get them on the stack for conservative
// stack scanning.
//
// See asm/x64/push_registers_clang.cc for why the function is not generated
// using clang.
//
// Do not depend on V8_TARGET_OS_* defines as some embedders may override the
// GN toolchain (e.g. ChromeOS) and not provide them.
// We maintain 8-byte alignment at calls by pushing an additional
// non-callee-saved register (r3).
//
// Calling convention source:
// https://en.wikipedia.org/wiki/Calling_convention#ARM_(A32)
// http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html
asm(".globl PushAllRegistersAndIterateStack \n"
".type PushAllRegistersAndIterateStack, %function \n"
".hidden PushAllRegistersAndIterateStack \n"
"PushAllRegistersAndIterateStack: \n"
// Push all callee-saved registers and save return address.
// Only {r4-r11} are callee-saved registers. Push r3 in addition to align
// the stack back to 8 bytes.
" push {r3-r11, lr} \n"
// Pass 1st parameter (r0) unchanged (Stack*).
// Pass 2nd parameter (r1) unchanged (StackVisitor*).
// Save 3rd parameter (r2; IterateStackCallback).
" mov r3, r2 \n"
// Pass 3rd parameter as sp (stack pointer).
" mov r2, sp \n"
// Call the callback.
" blx r3 \n"
// Discard all the registers.
" add sp, sp, #36 \n"
// Pop lr into pc which returns and switches mode if needed.
" pop {pc} \n");
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