[compiler][linkage] No allocation of slots after aligning a frame

- Adds DCHECKs to make sure no stack slots are allocated after
  aligning a frame.
- Changes Arm64 CodeGenerator::FinishFrame to align the frame after
  allocating callee-saved registers, and relaxes the constraints on
  the number of callee-saved registers.

Bug: v8:9198
Change-Id: Iacb0518b57fa3ea2ff801eda69719f4c32733850
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2694104Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72781}

src/compiler/backend/arm64/code-generator-arm64.cc

@@ -3050,7 +3050,6 @@ void CodeGenerator::AssembleArchTableSwitch(Instruction* instr) {
 }
 
 void CodeGenerator::FinishFrame(Frame* frame) {
-  frame->AlignFrame(16);
   auto call_descriptor = linkage()->GetIncomingDescriptor();
 
   // Save FP registers.
@@ -3059,7 +3058,6 @@ void CodeGenerator::FinishFrame(Frame* frame) {
   int saved_count = saves_fp.Count();
   if (saved_count != 0) {
     DCHECK(saves_fp.list() == CPURegList::GetCalleeSavedV().list());
-    DCHECK_EQ(saved_count % 2, 0);
     frame->AllocateSavedCalleeRegisterSlots(saved_count *
                                             (kDoubleSize / kSystemPointerSize));
   }
@@ -3068,9 +3066,9 @@ void CodeGenerator::FinishFrame(Frame* frame) {
                                 call_descriptor->CalleeSavedRegisters());
   saved_count = saves.Count();
   if (saved_count != 0) {
-    DCHECK_EQ(saved_count % 2, 0);
     frame->AllocateSavedCalleeRegisterSlots(saved_count);
   }
+  frame->AlignFrame(16);
 }
 
 void CodeGenerator::AssembleConstructFrame() {

src/compiler/frame.cc

@@ -20,6 +20,7 @@ Frame::Frame(int fixed_frame_size_in_slots)
 void Frame::AlignFrame(int alignment) {
 #if DEBUG
   spill_slots_finished_ = true;
+  frame_aligned_ = true;
 #endif
   // In the calculations below we assume that alignment is a power of 2.
   DCHECK(base::bits::IsPowerOfTwo(alignment));

src/compiler/frame.h

@@ -116,6 +116,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void AlignSavedCalleeRegisterSlots(int alignment = kDoubleSize) {
+    DCHECK(!frame_aligned_);
 #if DEBUG
     spill_slots_finished_ = true;
 #endif
@@ -127,6 +128,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void AllocateSavedCalleeRegisterSlots(int count) {
+    DCHECK(!frame_aligned_);
 #if DEBUG
     spill_slots_finished_ = true;
 #endif
@@ -138,6 +140,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
               fixed_slot_count_ + spill_slot_count_ + return_slot_count_);
     // Never allocate spill slots after the callee-saved slots are defined.
     DCHECK(!spill_slots_finished_);
+    DCHECK(!frame_aligned_);
     int actual_width = std::max({width, AlignedSlotAllocator::kSlotSize});
     int actual_alignment =
         std::max({alignment, AlignedSlotAllocator::kSlotSize});
@@ -164,6 +167,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void EnsureReturnSlots(int count) {
+    DCHECK(!frame_aligned_);
     return_slot_count_ = std::max(return_slot_count_, count);
   }
 
@@ -171,6 +175,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
 
   int ReserveSpillSlots(size_t slot_count) {
     DCHECK_EQ(0, spill_slot_count_);
+    DCHECK(!frame_aligned_);
     spill_slot_count_ += static_cast<int>(slot_count);
     slot_allocator_.AllocateUnaligned(static_cast<int>(slot_count));
     return slot_allocator_.Size() - 1;
@@ -187,6 +192,7 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   BitVector* allocated_double_registers_;
 #if DEBUG
   bool spill_slots_finished_ = false;
+  bool frame_aligned_ = false;
 #endif
 };