MIPS64: Optimize generated code size for deoptimization table entry.

Reuse optimization introduced in 6dee8884.

TEST=
BUG=

Review URL: https://codereview.chromium.org/960963002

Cr-Commit-Position: refs/heads/master@{#26888}

src/mips64/deoptimizer-mips64.cc

@@ -329,39 +329,66 @@ void Deoptimizer::EntryGenerator::Generate() {
 
 
 // Maximum size of a table entry generated below.
-const int Deoptimizer::table_entry_size_ = 11 * Assembler::kInstrSize;
+const int Deoptimizer::table_entry_size_ = 2 * Assembler::kInstrSize;
 
 void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
   Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm());
 
   // Create a sequence of deoptimization entries.
   // Note that registers are still live when jumping to an entry.
-  Label table_start;
+  Label table_start, done, done_special, trampoline_jump;
   __ bind(&table_start);
-  for (int i = 0; i < count(); i++) {
-    Label start;
-    __ bind(&start);
-    __ daddiu(sp, sp, -1 * kPointerSize);
-    // Jump over the remaining deopt entries (including this one).
-    // This code is always reached by calling Jump, which puts the target (label
-    // start) into t9.
-    const int remaining_entries = (count() - i) * table_entry_size_;
-    __ Daddu(t9, t9, remaining_entries);
-    // 'at' was clobbered so we can only load the current entry value here.
-    __ li(t8, i);
-    __ jr(t9);  // Expose delay slot.
-    __ sd(t8, MemOperand(sp, 0 * kPointerSize));  // In the delay slot.
-
-    // Pad the rest of the code.
-    while (table_entry_size_ > (masm()->SizeOfCodeGeneratedSince(&start))) {
-      __ nop();
+  int kMaxEntriesBranchReach =
+      (1 << (kImm16Bits - 2)) / (table_entry_size_ / Assembler::kInstrSize);
+
+  if (count() <= kMaxEntriesBranchReach) {
+    // Common case.
+    for (int i = 0; i < count(); i++) {
+      Label start;
+      __ bind(&start);
+      DCHECK(is_int16(i));
+      __ Branch(USE_DELAY_SLOT, &done);  // Expose delay slot.
+      __ li(at, i);                      // In the delay slot.
+
+      DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
     }
 
-    DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
-  }
+    DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
+              count() * table_entry_size_);
+    __ bind(&done);
+    __ Push(at);
+  } else {
+    // Uncommon case, the branch cannot reach.
+    // Create mini trampoline and adjust id constants to get proper value at
+    // the end of table.
+    for (int i = kMaxEntriesBranchReach; i > 1; i--) {
+      Label start;
+      __ bind(&start);
+      DCHECK(is_int16(i));
+      __ Branch(USE_DELAY_SLOT, &trampoline_jump);  // Expose delay slot.
+      __ li(at, -i);                                // In the delay slot.
+      DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
+    }
+    // Entry with id == kMaxEntriesBranchReach - 1.
+    __ bind(&trampoline_jump);
+    __ Branch(USE_DELAY_SLOT, &done_special);
+    __ li(at, -1);
+
+    for (int i = kMaxEntriesBranchReach; i < count(); i++) {
+      Label start;
+      __ bind(&start);
+      DCHECK(is_int16(i));
+      __ Branch(USE_DELAY_SLOT, &done);  // Expose delay slot.
+      __ li(at, i);                      // In the delay slot.
+    }
 
-  DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
-      count() * table_entry_size_);
+    DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
+              count() * table_entry_size_);
+    __ bind(&done_special);
+    __ daddiu(at, at, kMaxEntriesBranchReach);
+    __ bind(&done);
+    __ Push(at);
+  }
 }