[regalloc] Cleanup use of kMaxFpRegisters

Minor refactoring to introduce kMaxRegisters instead of relying on
the fact that kMaxGpRegisters <= kMaxFpRegisters.

Bug: v8:8562
Change-Id: If8221a799199c62d5262cfad762489a5088351c7
Reviewed-on: https://chromium-review.googlesource.com/c/1403120Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58687}

src/compiler/backend/register-allocator.cc

@@ -2806,10 +2806,6 @@ LinearScanAllocator::LinearScanAllocator(RegisterAllocationData* data,
       next_inactive_ranges_change_(LifetimePosition::Invalid()) {
   active_live_ranges().reserve(8);
   inactive_live_ranges().reserve(8);
-  // TryAllocateFreeReg and AllocateBlockedReg assume this
-  // when allocating local arrays.
-  DCHECK_GE(RegisterConfiguration::kMaxFPRegisters,
-            this->data()->config()->num_general_registers());
 }
 
 void LinearScanAllocator::AllocateRegisters() {
@@ -3121,9 +3117,8 @@ void LinearScanAllocator::FindFreeRegistersForRange(
 // - a phi. The same analysis as in the case of the input constraint applies.
 //
 void LinearScanAllocator::ProcessCurrentRange(LiveRange* current) {
-  LifetimePosition free_until_pos_buff[RegisterConfiguration::kMaxFPRegisters];
-  Vector<LifetimePosition> free_until_pos(
-      free_until_pos_buff, RegisterConfiguration::kMaxFPRegisters);
+  EmbeddedVector<LifetimePosition, RegisterConfiguration::kMaxRegisters>
+      free_until_pos;
   FindFreeRegistersForRange(current, free_until_pos);
   if (!TryAllocatePreferredReg(current, free_until_pos)) {
     if (current->TopLevel()->IsSplinter()) {
@@ -3245,8 +3240,8 @@ void LinearScanAllocator::AllocateBlockedReg(LiveRange* current) {
   // use_pos keeps track of positions a register/alias is used at.
   // block_pos keeps track of positions where a register/alias is blocked
   // from.
-  LifetimePosition use_pos[RegisterConfiguration::kMaxFPRegisters];
-  LifetimePosition block_pos[RegisterConfiguration::kMaxFPRegisters];
+  LifetimePosition use_pos[RegisterConfiguration::kMaxRegisters];
+  LifetimePosition block_pos[RegisterConfiguration::kMaxRegisters];
   for (int i = 0; i < num_regs; i++) {
     use_pos[i] = block_pos[i] = LifetimePosition::MaxPosition();
   }

src/compiler/backend/register-allocator.h

@@ -242,11 +242,7 @@ enum class UsePositionHintType : uint8_t {
   kUnresolved
 };
 
-static const int32_t kUnassignedRegister =
-    RegisterConfiguration::kMaxGeneralRegisters;
-
-static_assert(kUnassignedRegister <= RegisterConfiguration::kMaxFPRegisters,
-              "kUnassignedRegister too small");
+static const int32_t kUnassignedRegister = RegisterConfiguration::kMaxRegisters;
 
 // Representation of a use position.
 class V8_EXPORT_PRIVATE UsePosition final

src/register-configuration.h

@@ -9,6 +9,7 @@
 #include "src/globals.h"
 #include "src/machine-type.h"
 #include "src/reglist.h"
+#include "src/utils.h"
 
 namespace v8 {
 namespace internal {
@@ -25,8 +26,10 @@ class V8_EXPORT_PRIVATE RegisterConfiguration {
   };
 
   // Architecture independent maxes.
-  static const int kMaxGeneralRegisters = 32;
-  static const int kMaxFPRegisters = 32;
+  static constexpr int kMaxGeneralRegisters = 32;
+  static constexpr int kMaxFPRegisters = 32;
+  static constexpr int kMaxRegisters =
+      Max(kMaxFPRegisters, kMaxGeneralRegisters);
 
   // Default RegisterConfigurations for the target architecture.
   static const RegisterConfiguration* Default();