1 files changed, 39 insertions, 0 deletions
diff --git a/deps/v8/src/heap/base/asm/arm/push_registers_asm.cc b/deps/v8/src/heap/base/asm/arm/push_registers_asm.cc
new file mode 100644
index 0000000000..5246c3f6c3
--- /dev/null
+++ b/deps/v8/src/heap/base/asm/arm/push_registers_asm.cc
@@ -0,0 +1,39 @@
+// 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");