Reland "cppgc: Try to fix test IteratePointersFindsCalleeSavedRegisters, vol.2"

Fix crash on Mac64 Debug build. The reason of the failure: misaligned
stack. Fix: apply attribute to force the stack be realigned.

Original description:
> The previous attempt has broken the tsan bot. The only reliable way to
> make sure that registers are not clobbered is by doing direct call from
> inline assembly, which is what this CL does.

> Change-Id: I6adbd5e735949a7cc4cc7fc686ee8c428863ffb9
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2859947
> Commit-Queue: Anton Bikineev <bikineev@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74313}

Change-Id: I842d6876c2cf287cfe74e53e7cb45028dff61a56
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2865748
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74336}

test/unittests/heap/cppgc/stack-unittest.cc

@@ -305,6 +305,26 @@ TEST_F(GCStackTest, IteratePointersFindsParameterNesting8) {
 
 #ifdef FOR_ALL_CALLEE_SAVED_REGS
 
+namespace {
+// We manually call into this function from inline assembly. Therefore we need
+// to make sure that:
+// 1) there is no .plt indirection (i.e. visibility is hidden);
+// 2) stack is realigned in the function prologue.
+V8_NOINLINE
+#if !defined(V8_OS_WIN)
+__attribute__((visibility("hidden")))
+#endif
+#ifdef __has_attribute
+#if __has_attribute(force_align_arg_pointer)
+__attribute__((force_align_arg_pointer))
+#endif
+#endif
+extern "C" void
+IteratePointersNoMangling(Stack* stack, StackVisitor* visitor) {
+  stack->IteratePointers(visitor);
+}
+}  // namespace
+
 TEST_F(GCStackTest, IteratePointersFindsCalleeSavedRegisters) {
   auto scanner = std::make_unique<StackScanner>();
 
@@ -321,22 +341,37 @@ TEST_F(GCStackTest, IteratePointersFindsCalleeSavedRegisters) {
   auto* local_stack = GetStack();
   auto* local_scanner = scanner.get();
 
+#define MOVE_TO_REG_AND_CALL_IMPL(needle_reg, arg1, arg2)           \
+  asm volatile("mov %0, %%" needle_reg "\n mov %1, %%" arg1         \
+               "\n mov %2, %%" arg2                                 \
+               "\n call %P3"                                        \
+               "\n mov $0, %%" needle_reg                           \
+               :                                                    \
+               : "r"(local_scanner->needle()), "r"(local_stack),    \
+                 "r"(local_scanner), "i"(IteratePointersNoMangling) \
+               : "memory", needle_reg, arg1, arg2, "cc");
+
+#ifdef V8_OS_WIN
+#define MOVE_TO_REG_AND_CALL(reg) MOVE_TO_REG_AND_CALL_IMPL(reg, "rcx", "rdx")
+#else  // !V8_OS_WIN
+#define MOVE_TO_REG_AND_CALL(reg) MOVE_TO_REG_AND_CALL_IMPL(reg, "rdi", "rsi")
+#endif  // V8_OS_WIN
+
 // Moves |local_scanner->needle()| into a callee-saved register, leaving the
 // callee-saved register as the only register referencing the needle.
 // (Ignoring implementation-dependent dirty registers/stack.)
 #define KEEP_ALIVE_FROM_CALLEE_SAVED(reg)                                     \
   local_scanner->Reset();                                                     \
-  /* This moves the temporary into the calee-saved register. */          \
-  asm("mov %0, %%" reg : : "r"(local_scanner->needle()) : reg);          \
-  /* Register is unprotected from here till the actual invocation. */    \
-  local_stack->IteratePointers(local_scanner);                           \
+  /* Wrap the inline assembly in a lambda to rely on the compiler for saving  \
+  caller-saved registers. */                                                  \
+  [local_stack, local_scanner]() V8_NOINLINE { MOVE_TO_REG_AND_CALL(reg) }(); \
   EXPECT_TRUE(local_scanner->found())                                         \
       << "pointer in callee-saved register not found. register: " << reg      \
-      << std::endl;                                                      \
-  /* Clear out the register again */                                     \
-  asm("mov $0, %%" reg : : : reg);
+      << std::endl;
 
   FOR_ALL_CALLEE_SAVED_REGS(KEEP_ALIVE_FROM_CALLEE_SAVED)
+#undef MOVE_TO_REG_AND_CALL
+#undef MOVE_TO_REG_AND_CALL_IMPL
 #undef KEEP_ALIVE_FROM_CALLEE_SAVED
 #undef FOR_ALL_CALLEE_SAVED_REGS
 }