cppgc: Add test for stack alignment

This tests that the stack doesn't get misaligned after asm trampolines.
x86 and x64 psABI requires the stack to be 16 bytes aligned.

Bug: chromium:1056170
Change-Id: I73e7100806c6ecf3f5e884a121a15bcc384d8011
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2128048Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66922}

test/unittests/heap/cppgc/stack_unittest.cc

@@ -11,6 +11,10 @@
 #include "src/base/platform/platform.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if V8_OS_LINUX && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
+#include <xmmintrin.h>
+#endif
+
 namespace cppgc {
 namespace internal {
 
@@ -233,6 +237,22 @@ TEST_F(GCStackTest, IteratePointersFindsCalleeSavedRegisters) {
 #undef FOR_ALL_CALLEE_SAVED_REGS
 }
 
+#if V8_OS_LINUX && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
+class CheckStackAlignmentVisitor final : public StackVisitor {
+ public:
+  void VisitPointer(const void*) final {
+    float f[4] = {0.};
+    volatile auto xmm = ::_mm_load_ps(f);
+    USE(xmm);
+  }
+};
+
+TEST_F(GCStackTest, StackAlignment) {
+  auto checker = std::make_unique<CheckStackAlignmentVisitor>();
+  GetStack()->IteratePointers(checker.get());
+}
+#endif  // V8_OS_LINUX && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
+
 #endif  // CONSERVATIVE_STACK_SCAN_SUPPORTED
 
 }  // namespace internal