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

This reverts commit b18bc221.

Reason for revert: Rolling back to previous greedy slot allocator.

tbr=jgruber@chromium.org

Original change's description:
> [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/+/2694104
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Commit-Queue: Bill Budge <bbudge@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#72781}

Bug: v8:9198
Change-Id: I53f415b7b0f73b57db24859d1199c6a44f911035
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2713204
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72930}

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

@@ -3051,6 +3051,7 @@ void CodeGenerator::AssembleArchTableSwitch(Instruction* instr) {
 }
 
 void CodeGenerator::FinishFrame(Frame* frame) {
+  frame->AlignFrame(16);
   auto call_descriptor = linkage()->GetIncomingDescriptor();
 
   // Save FP registers.
@@ -3059,6 +3060,7 @@ 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));
   }
@@ -3067,9 +3069,9 @@ 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

@@ -20,7 +20,6 @@ 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

@@ -116,7 +116,6 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void AlignSavedCalleeRegisterSlots(int alignment = kDoubleSize) {
-    DCHECK(!frame_aligned_);
 #if DEBUG
     spill_slots_finished_ = true;
 #endif
@@ -128,7 +127,6 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void AllocateSavedCalleeRegisterSlots(int count) {
-    DCHECK(!frame_aligned_);
 #if DEBUG
     spill_slots_finished_ = true;
 #endif
@@ -140,7 +138,6 @@ 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});
@@ -167,7 +164,6 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   }
 
   void EnsureReturnSlots(int count) {
-    DCHECK(!frame_aligned_);
     return_slot_count_ = std::max(return_slot_count_, count);
   }
 
@@ -175,7 +171,6 @@ 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;
@@ -192,7 +187,6 @@ class V8_EXPORT_PRIVATE Frame : public ZoneObject {
   BitVector* allocated_double_registers_;
 #if DEBUG
   bool spill_slots_finished_ = false;
-  bool frame_aligned_ = false;
 #endif
 };