cppgc: Use inline asm to generate x64 stack scanning trampoline

Use inline asm to generate the x64 PushAllRegistersAndIterateStack
which is the trampoline for conservative stack scanning. Keep the
function definition as C code to allow clang to generate the correct
mangling for each platform.

This approach has the benefit that it immediately works for all
platforms that support clang.

Bug: chromium:1056170
Change-Id: Ic7a1c1b57e67ae1442bd8bda4e55d89112facfc7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2132787Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66958}

BUILD.gn

@@ -346,6 +346,15 @@ config("libbase_config") {
   }
 }
 
+# This config should be applied to code using the cppgc_base.
+config("cppgc_base_config") {
+  if (target_cpu == "x64") {
+    if (is_clang) {
+      defines = [ "CPPGC_SUPPORTS_CONSERVATIVE_STACK_SCAN" ]
+    }
+  }
+}
+
 # This config should be applied to code using the libsampler.
 config("libsampler_config") {
   include_dirs = [ "include" ]
@@ -3955,12 +3964,15 @@ v8_source_set("cppgc_base") {
   ]
 
   if (target_cpu == "x64") {
-    if (!is_win) {
-      sources += [ "src/heap/cppgc/asm/x64/push_registers.S" ]
+    if (is_clang) {
+      sources += [ "src/heap/cppgc/asm/x64/push_registers_clang.cc" ]
     }
   }
 
-  configs = [ ":internal_config" ]
+  configs = [
+    ":internal_config",
+    ":cppgc_base_config",
+  ]
 
   public_deps = [ ":v8_libbase" ]
 }

src/heap/cppgc/asm/x64/push_registers.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.
-
-.att_syntax
-
-.text
-
-#if defined(V8_TARGET_OS_MACOSX) || defined(V8_TARGET_OS_IOS)
-
-.globl _PushAllRegistersAndIterateStack
-_PushAllRegistersAndIterateStack:
-
-#else  // !(defined(V8_TARGET_OS_MACOSX) || defined(V8_TARGET_OS_IOS))
-
-.type PushAllRegistersAndIterateStack, %function
-.global PushAllRegistersAndIterateStack
-.hidden PushAllRegistersAndIterateStack
-PushAllRegistersAndIterateStack:
-
-#endif  // !(defined(V8_TARGET_OS_MACOSX) || defined(V8_TARGET_OS_IOS))
-
-    // 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 56 bytes which maintains 16-byte stack alignment
-    // at the call.
-    // Source: https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf
-    //
-    // rbp is callee-saved. Maintain proper frame pointer for debugging.
-    push %rbp
-    mov %rsp, %rbp
-    push $0xCDCDCD  // Dummy for alignment.
-    push %rbx
-    push %r12
-    push %r13
-    push %r14
-    push %r15
-    // Pass 1st parameter (rdi) unchanged (Stack*).
-    // Pass 2nd parameter (rsi) unchanged (StackVisitor*).
-    // Save 3rd parameter (rdx; IterateStackCallback)
-    mov %rdx, %r8
-    // Pass 3rd parameter as rsp (stack pointer).
-    mov %rsp, %rdx
-    // Call the callback.
-    call *%r8
-    // Pop the callee-saved registers.
-    add $48, %rsp
-    // Restore rbp as it was used as frame pointer.
-    pop %rbp
-    ret

src/heap/cppgc/asm/x64/push_registers_clang.cc

+// 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.
+
+#ifndef V8_HAVE_TARGET_OS
+#error "File assumes V8_TARGET_OS_* defines are present"
+#endif  // V8_HAVE_TARGET_OS
+
+// Push all callee-saved registers to get them on the stack for conservative
+// stack scanning.
+//
+// Do not add any C code to the function. The function is naked to avoid
+// emitting a prologue/epilogue that could violate alginment computations.
+extern "C" __attribute__((naked, noinline)) void
+PushAllRegistersAndIterateStack(void* /* {Stack*} */,
+                                void* /* {StackVisitor*} */,
+                                void* /* {IterateStackCallback} */) {
+#ifdef V8_TARGET_OS_WIN
+
+  // 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
+  asm volatile(
+      // rbp is callee-saved. Maintain proper frame pointer for debugging.
+      " push %rbp           \n"
+      " mov %rsp, %rbp      \n"
+      // Dummy for alignment.
+      " push $0xCDCDCD      \n"
+      " push %rsi           \n"
+      " push %rdi           \n"
+      " push %rbx           \n"
+      " push %r12           \n"
+      " push %r13           \n"
+      " push %r14           \n"
+      " push %r15           \n"
+      // Pass 1st parameter (rcx) unchanged (Stack*).
+      // Pass 2nd parameter (rdx) unchanged (StackVisitor*).
+      // Save 3rd parameter (r8; IterateStackCallback)
+      " mov %r8, %r9        \n"
+      // Pass 3rd parameter as rsp (stack pointer).
+      " mov %rsp, %r8       \n"
+      // Call the callback.
+      " call *%r9           \n"
+      // Pop the callee-saved registers.
+      " add $64, %rsp       \n"
+      // Restore rbp as it was used as frame pointer.
+      " pop %rbp            \n"
+      " ret                 \n");
+
+#else  // !V8_TARGET_OS_WIN
+
+  // We maintain 16-byte alignment at calls. There is an 8-byte return address
+  // on the stack and we push 56 bytes which maintains 16-byte stack alignment
+  // at the call.
+  // Source: https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf
+  asm volatile(
+      // rbp is callee-saved. Maintain proper frame pointer for debugging.
+      " push %rbp           \n"
+      " mov %rsp, %rbp      \n"
+      // Dummy for alignment.
+      " push $0xCDCDCD      \n"
+      " push %rbx           \n"
+      " push %r12           \n"
+      " push %r13           \n"
+      " push %r14           \n"
+      " push %r15           \n"
+      // Pass 1st parameter (rdi) unchanged (Stack*).
+      // Pass 2nd parameter (rsi) unchanged (StackVisitor*).
+      // Save 3rd parameter (rdx; IterateStackCallback)
+      " mov %rdx, %r8       \n"
+      // Pass 3rd parameter as rsp (stack pointer).
+      " mov %rsp, %rdx      \n"
+      // Call the callback.
+      " call *%r8           \n"
+      // Pop the callee-saved registers.
+      " add $48, %rsp       \n"
+      // Restore rbp as it was used as frame pointer.
+      " pop %rbp            \n"
+      " ret                 \n");
+
+#endif  // !V8_TARGET_OS_WIN
+}

src/heap/cppgc/stack.h

@@ -7,17 +7,6 @@
 
 #include "src/base/macros.h"
 
-// TODO(chromium:1056170): Implement all platforms.
-// TODO(chromium:1056170): Should use HOST arch instead of target arch. Fix
-// 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 {
 

test/unittests/BUILD.gn

@@ -58,6 +58,7 @@ v8_source_set("cppgc_unittests_sources") {
   configs = [
     "../..:external_config",
     "../..:internal_config_base",
+    "../..:cppgc_base_config",
   ]
 
   deps = [