Define a constant for the return address stack slot count

... to avoid the repeated pattern of calculating it.

Bug: v8:8888
Change-Id: I4af5264aae6cfb8b6232b5aaf9ceb2cb568c29d0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2362692
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69469}

src/base/build_config.h

@@ -199,6 +199,8 @@
 #else
 #define V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK false
 #endif
+constexpr int kReturnAddressStackSlotCount =
+    V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? 1 : 0;
 
 // Number of bits to represent the page size for paged spaces.
 #if defined(V8_TARGET_ARCH_PPC) || defined(V8_TARGET_ARCH_PPC64)

src/compiler/backend/code-generator.cc

@@ -597,6 +597,8 @@ bool CodeGenerator::IsValidPush(InstructionOperand source,
 void CodeGenerator::GetPushCompatibleMoves(Instruction* instr,
                                            PushTypeFlags push_type,
                                            ZoneVector<MoveOperands*>* pushes) {
+  static constexpr int first_push_compatible_index =
+      kReturnAddressStackSlotCount;
   pushes->clear();
   for (int i = Instruction::FIRST_GAP_POSITION;
        i <= Instruction::LAST_GAP_POSITION; ++i) {
@@ -607,8 +609,6 @@ void CodeGenerator::GetPushCompatibleMoves(Instruction* instr,
       for (auto move : *parallel_move) {
         InstructionOperand source = move->source();
         InstructionOperand destination = move->destination();
-        int first_push_compatible_index =
-            V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? 1 : 0;
         // If there are any moves from slots that will be overridden by pushes,
         // then the full gap resolver must be used since optimization with
         // pushes don't participate in the parallel move and might clobber

src/compiler/backend/instruction-selector.cc

@@ -2972,9 +2972,8 @@ void InstructionSelector::VisitTailCall(Node* node) {
   int optional_padding_slot = callee->GetFirstUnusedStackSlot();
   buffer.instruction_args.push_back(g.TempImmediate(optional_padding_slot));
 
-  int first_unused_stack_slot =
-      (V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? true : false) +
-      stack_param_delta;
+  const int first_unused_stack_slot =
+      kReturnAddressStackSlotCount + stack_param_delta;
   buffer.instruction_args.push_back(g.TempImmediate(first_unused_stack_slot));
 
   // Emit the tailcall instruction.

test/cctest/compiler/test-code-generator.cc

@@ -1137,8 +1137,7 @@ class CodeGeneratorTester {
     sequence->AddInstruction(Instruction::New(zone_, kArchPrepareTailCall));
 
     // We use either zero or one slots.
-    int first_unused_stack_slot =
-        V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? 1 : 0;
+    static constexpr int first_unused_stack_slot = kReturnAddressStackSlotCount;
     int optional_padding_slot = first_unused_stack_slot;
     InstructionOperand callee[] = {
         AllocatedOperand(LocationOperand::REGISTER,
@@ -1323,7 +1322,7 @@ TEST(AssembleTailCallGap) {
                                        MachineRepresentation::kTagged, -1);
 
   // Avoid slot 0 for architectures which use it store the return address.
-  int first_slot = V8_TARGET_ARCH_STORES_RETURN_ADDRESS_ON_STACK ? 1 : 0;
+  static constexpr int first_slot = kReturnAddressStackSlotCount;
   auto slot_0 = AllocatedOperand(LocationOperand::STACK_SLOT,
                                  MachineRepresentation::kTagged, first_slot);
   auto slot_1 =