[ic] Fix megamorphic stub cache probing on some platforms.

src/ic/arm64/stub-cache-arm64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
 #include "src/ic/stub-cache.h"
 #include "src/interface-descriptors.h"
 
 namespace v8 {
 namespace internal {
 
 
 #define __ ACCESS_MASM(masm)
 
 
 // Probe primary or secondary table.
 // If the entry is found in the cache, the generated code jump to the first
 // instruction of the stub in the cache.
 // If there is a miss the code fall trough.
 //
 // 'receiver', 'name' and 'offset' registers are preserved on miss.
 static void ProbeTable(StubCache* stub_cache, MacroAssembler* masm,
                        Code::Flags flags, StubCache::Table table,
-                       Register receiver, Register name, Register offset,
-                       Register scratch, Register scratch2, Register scratch3) {
+                       Register receiver, Register name,
+                       // The offset is scaled by 4, based on
+                       // kCacheIndexShift, which is two bits
+                       Register offset, Register scratch, Register scratch2,
+                       Register scratch3) {
   // Some code below relies on the fact that the Entry struct contains
   // 3 pointers (name, code, map).
   STATIC_ASSERT(sizeof(StubCache::Entry) == (3 * kPointerSize));
 
   ExternalReference key_offset(stub_cache->key_reference(table));
   ExternalReference value_offset(stub_cache->value_reference(table));
   ExternalReference map_offset(stub_cache->map_reference(table));
 
   uintptr_t key_off_addr = reinterpret_cast<uintptr_t>(key_offset.address());
   uintptr_t value_off_addr =
       reinterpret_cast<uintptr_t>(value_offset.address());
   uintptr_t map_off_addr = reinterpret_cast<uintptr_t>(map_offset.address());
 
   Label miss;
 
   DCHECK(!AreAliased(name, offset, scratch, scratch2, scratch3));
 
   // Multiply by 3 because there are 3 fields per entry.
   __ Add(scratch3, offset, Operand(offset, LSL, 1));
 
   // Calculate the base address of the entry.
   __ Mov(scratch, key_offset);
-  __ Add(scratch, scratch, Operand(scratch3, LSL, kPointerSizeLog2));
+  __ Add(
+      scratch, scratch,
+      Operand(scratch3, LSL, kPointerSizeLog2 - StubCache::kCacheIndexShift));
 
   // Check that the key in the entry matches the name.
   __ Ldr(scratch2, MemOperand(scratch));
   __ Cmp(name, scratch2);
   __ B(ne, &miss);
 
   // Check the map matches.
   __ Ldr(scratch2, MemOperand(scratch, map_off_addr - key_off_addr));
   __ Ldr(scratch3, FieldMemOperand(receiver, HeapObject::kMapOffset));
   __ Cmp(scratch2, scratch3);
@@ skipping 59 matching lines @@
 #endif
 
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->megamorphic_stub_cache_probes(), 1, extra2,
                       extra3);
 
   // Check that the receiver isn't a smi.
   __ JumpIfSmi(receiver, &miss);
 
   // Compute the hash for primary table.
-  __ Ldr(scratch, FieldMemOperand(name, Name::kHashFieldOffset));
+  __ Ldr(scratch.W(), FieldMemOperand(name, Name::kHashFieldOffset));
   __ Ldr(extra, FieldMemOperand(receiver, HeapObject::kMapOffset));
   __ Add(scratch, scratch, extra);
   __ Eor(scratch, scratch, flags);
-  // We shift out the last two bits because they are not part of the hash.
-  __ Ubfx(scratch, scratch, kCacheIndexShift,
-          CountTrailingZeros(kPrimaryTableSize, 64));
+  __ And(scratch, scratch,
+         Operand((kPrimaryTableSize - 1) << kCacheIndexShift));
 
   // Probe the primary table.
   ProbeTable(this, masm, flags, kPrimary, receiver, name, scratch, extra,
              extra2, extra3);
 
   // Primary miss: Compute hash for secondary table.
-  __ Sub(scratch, scratch, Operand(name, LSR, kCacheIndexShift));
-  __ Add(scratch, scratch, flags >> kCacheIndexShift);
-  __ And(scratch, scratch, kSecondaryTableSize - 1);
+  __ Sub(scratch, scratch, Operand(name));
+  __ Add(scratch, scratch, Operand(flags));
+  __ And(scratch, scratch,
+         Operand((kSecondaryTableSize - 1) << kCacheIndexShift));
 
   // Probe the secondary table.
   ProbeTable(this, masm, flags, kSecondary, receiver, name, scratch, extra,
              extra2, extra3);
 
   // Cache miss: Fall-through and let caller handle the miss by
   // entering the runtime system.
   __ Bind(&miss);
   __ IncrementCounter(counters->megamorphic_stub_cache_misses(), 1, extra2,
                       extra3);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64