cppgc: Remove Win stack scanning support

Even though the default toolchain for assembly on Windows uses MASM
assemblers, we are not supposed to use them to support Linux/Win
cross-compile.

Bug: chromium:1056170, chromium:1066834
Change-Id: If17dbd68915f843e3fb47584560a4667d5c35bc7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2132250Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66951}

BUILD.gn

@@ -3955,9 +3955,7 @@ v8_source_set("cppgc_base") {
   ]
 
   if (target_cpu == "x64") {
-    if (is_win) {
-      sources += [ "src/heap/cppgc/asm/x64/push_registers_win.S" ]
-    } else {
+    if (!is_win) {
       sources += [ "src/heap/cppgc/asm/x64/push_registers.S" ]
     }
   }

src/heap/cppgc/asm/x64/push_registers_win.S

-;; 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.
-
-;; MASM syntax
-;; https://docs.microsoft.com/en-us/cpp/assembler/masm/microsoft-macro-assembler-reference?view=vs-2019
-
-public PushAllRegistersAndIterateStack
-
-.code
-PushAllRegistersAndIterateStack:
-    ;; Push all callee-saved registers to get them on the stack for conservative
-    ;; stack scanning.
-    ;;
-    ;; We maintain 16-byte alignment at calls. There is an 8-byte return address
-    ;; on the stack and we push 72 bytes which maintains 16-byte stack alignment
-    ;; at the call.
-    ;; Source: https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention
-    ;;
-    ;; rbp is callee-saved. Maintain proper frame pointer for debugging.
-    push rbp
-    mov rbp, rsp
-    push 0CDCDCDh  ;; Dummy for alignment.
-    push rsi
-    push rdi
-    push rbx
-    push r12
-    push r13
-    push r14
-    push r15
-    ;; Pass 1st parameter (rcx) unchanged (Stack*).
-    ;; Pass 2nd parameter (rdx) unchanged (StackVisitor*).
-    ;; Save 3rd parameter (r8; IterateStackCallback)
-    mov r9, r8
-    ;; Pass 3rd parameter as rsp (stack pointer).
-    mov r8, rsp
-    ;; Call the callback.
-    call r9
-    ;; Pop the callee-saved registers.
-    add rsp, 64
-    ;; Restore rbp as it was used as frame pointer.
-    pop rbp
-    ret
-
-end

src/heap/cppgc/stack.h

@@ -12,9 +12,11 @@
 // requires fixing e.g. simulator platforms.
 #ifdef __clang__
 #if defined(V8_TARGET_ARCH_X64)
+#if !defined(V8_TARGET_OS_WIN)
 #define CPPGC_SUPPORTS_CONSERVATIVE_STACK_SCAN 1
 #endif
 #endif
+#endif
 
 namespace cppgc {
 namespace internal {