MIPS: Simplify the deopt entry method.

src/mips/deoptimizer-mips.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 923 matching lines @@
   __ InitializeRootRegister();
 
   __ pop(at);  // Get continuation, leave pc on stack.
   __ pop(ra);
   __ Jump(at);
   __ stop("Unreachable.");
 }
 
 
 // Maximum size of a table entry generated below.
-const int Deoptimizer::table_entry_size_ = 12 * Assembler::kInstrSize;
+const int Deoptimizer::table_entry_size_ = 9 * Assembler::kInstrSize;
 
 void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
   Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm());
 
   // Create a sequence of deoptimization entries. Note that any
   // registers may be still live.
   Label table_start;
   __ bind(&table_start);
   for (int i = 0; i < count(); i++) {
     Label start;
     __ bind(&start);
     if (type() != EAGER) {
       // Emulate ia32 like call by pushing return address to stack.
-      __ addiu(sp, sp, -3 * kPointerSize);
-      __ sw(ra, MemOperand(sp, 2 * kPointerSize));
+      __ addiu(sp, sp, -2 * kPointerSize);
+      __ sw(ra, MemOperand(sp, 1 * kPointerSize));
     } else {
-      __ addiu(sp, sp, -2 * kPointerSize);
+      __ addiu(sp, sp, -1 * kPointerSize);
     }
-    // Using ori makes sure only one instruction is generated. This will work
-    // as long as the number of deopt entries is below 2^16.
-    __ ori(at, zero_reg, i);
-    __ sw(at, MemOperand(sp, kPointerSize));
-    __ sw(ra, MemOperand(sp, 0));
-    // This branch instruction only jumps over one instruction, and that is
-    // executed in the delay slot. The result is that execution is linear but
-    // the ra register is updated.
-    __ bal(1);
     // Jump over the remaining deopt entries (including this one).
-    // Only include the remaining part of the current entry in the calculation.
+    // 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_;
-    const int cur_size = masm()->SizeOfCodeGeneratedSince(&start);
-    // ra points to the instruction after the delay slot. Adjust by 4.
-    __ Addu(at, ra, remaining_entries - cur_size - Assembler::kInstrSize);
-    __ lw(ra, MemOperand(sp, 0));
-    __ jr(at);  // Expose delay slot.
-    __ addiu(sp, sp, kPointerSize);  // In delay slot.
+    __ Addu(t9, t9, remaining_entries);
+    // 'at' was clobbered so we can only load the current entry value here.
+    __ li(at, i);
+    __ jr(t9);  // Expose delay slot.
+    __ sw(at, MemOperand(sp, 0 * kPointerSize));  // In the delay slot.
 
     // Pad the rest of the code.
     while (table_entry_size_ > (masm()->SizeOfCodeGeneratedSince(&start))) {
       __ nop();
     }
 
     ASSERT_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
   }
 
   ASSERT_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
       count() * table_entry_size_);
 }
 
 #undef __
 
 
 } }  // namespace v8::internal