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

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

Index: src/ic/mips/stub-cache-mips.cc
diff --git a/src/ic/mips/stub-cache-mips.cc b/src/ic/mips/stub-cache-mips.cc
index e4dbcc6cd4d3500e0c2107b081f726c7dae38568..5433d0d8530fed31cb41577e492730c2d9f0c726 100644
--- a/src/ic/mips/stub-cache-mips.cc
+++ b/src/ic/mips/stub-cache-mips.cc
@@ -45,7 +45,7 @@ static void ProbeTable(StubCache* stub_cache, MacroAssembler* masm,
 
   // Calculate the base address of the entry.
   __ li(base_addr, Operand(key_offset));
-  __ Lsa(base_addr, base_addr, offset_scratch, kPointerSizeLog2);
+  __ Addu(base_addr, base_addr, offset_scratch);
 
   // Check that the key in the entry matches the name.
   __ lw(at, MemOperand(base_addr, 0));
@@ -134,23 +134,21 @@ void StubCache::GenerateProbe(MacroAssembler* masm, Register receiver,
   __ lw(scratch, FieldMemOperand(name, Name::kHashFieldOffset));
   __ lw(at, FieldMemOperand(receiver, HeapObject::kMapOffset));
   __ Addu(scratch, scratch, at);
-  uint32_t mask = kPrimaryTableSize - 1;
-  // We shift out the last two bits because they are not part of the hash and
-  // they are always 01 for maps.
-  __ srl(scratch, scratch, kCacheIndexShift);
-  __ Xor(scratch, scratch, Operand((flags >> kCacheIndexShift) & mask));
-  __ And(scratch, scratch, Operand(mask));
+  __ Xor(scratch, scratch, Operand(flags));
+  __ li(at, Operand(kPrimaryTableSize - 1));
+  __ sll(at, at, kCacheIndexShift);

[Jakob Kummerow, 2016/07/20 12:09:45]

Why not fold this into the instruction above?

__ li(at, Operand((kPrimaryTableSize - 1) << kCacheIndexShift));

Again below.

[Igor Sheludko, 2016/07/20 13:40:26]

Done.

+  __ And(scratch, scratch, at);
 
   // Probe the primary table.
   ProbeTable(this, masm, flags, kPrimary, receiver, name, scratch, extra,
              extra2, extra3);
 
   // Primary miss: Compute hash for secondary probe.
-  __ srl(at, name, kCacheIndexShift);
-  __ Subu(scratch, scratch, at);
-  uint32_t mask2 = kSecondaryTableSize - 1;
-  __ Addu(scratch, scratch, Operand((flags >> kCacheIndexShift) & mask2));
-  __ And(scratch, scratch, Operand(mask2));
+  __ Subu(scratch, scratch, name);
+  __ Addu(scratch, scratch, Operand(flags));
+  __ li(at, Operand(kSecondaryTableSize - 1));
+  __ sll(at, at, kCacheIndexShift);
+  __ And(scratch, scratch, at);
 
   // Probe the secondary table.
   ProbeTable(this, masm, flags, kSecondary, receiver, name, scratch, extra,