ARM: Optimisations for call, jump and untag....

src/arm/lithium-codegen-arm.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 3596 matching lines @@
   ASSERT(input->IsRegister() && input->Equals(instr->result()));
   ASSERT(!instr->hydrogen_value()->CheckFlag(HValue::kCanOverflow));
   __ SmiTag(ToRegister(input));
 }
 
 
 void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister() && input->Equals(instr->result()));
   if (instr->needs_check()) {
-    __ tst(ToRegister(input), Operand(kSmiTagMask));
-    DeoptimizeIf(ne, instr->environment());
+    ASSERT(kHeapObjectTag == 1);
+    // If the input is a HeapObject, SmiUntag will set the carry flag.
+    __ SmiUntag(ToRegister(input), SetCC);
+    DeoptimizeIf(cs, instr->environment());
+  } else {
+    __ SmiUntag(ToRegister(input));
   }
-  __ SmiUntag(ToRegister(input));
 }
 
 
 void LCodeGen::EmitNumberUntagD(Register input_reg,
                                 DoubleRegister result_reg,
                                 LEnvironment* env) {
   Register scratch = scratch0();
   SwVfpRegister flt_scratch = s0;
   ASSERT(!result_reg.is(d0));
 
@@ skipping 50 matching lines @@
   Register scratch1 = scratch0();
   Register scratch2 = ToRegister(instr->TempAt(0));
   DwVfpRegister double_scratch = double_scratch0();
   SwVfpRegister single_scratch = double_scratch.low();
 
   ASSERT(!scratch1.is(input_reg) && !scratch1.is(scratch2));
   ASSERT(!scratch2.is(input_reg) && !scratch2.is(scratch1));
 
   Label done;
 
+  // The input was optimistically untagged; revert it.
+  // The carry flag is set when we reach this deferred code as we just executed
+  // SmiUntag(heap_object, SetCC)
+  ASSERT(kHeapObjectTag == 1);
+  __ adc(input_reg, input_reg, Operand(input_reg));
+
   // Heap number map check.
   __ ldr(scratch1, FieldMemOperand(input_reg, HeapObject::kMapOffset));
   __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
   __ cmp(scratch1, Operand(ip));
 
   if (instr->truncating()) {
     Register scratch3 = ToRegister(instr->TempAt(1));
     DwVfpRegister double_scratch2 = ToDoubleRegister(instr->TempAt(2));
     ASSERT(!scratch3.is(input_reg) &&
            !scratch3.is(scratch1) &&
@@ skipping 52 matching lines @@
 
 void LCodeGen::DoTaggedToI(LTaggedToI* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister());
   ASSERT(input->Equals(instr->result()));
 
   Register input_reg = ToRegister(input);
 
   DeferredTaggedToI* deferred = new DeferredTaggedToI(this, instr);
 
-  // Smi check.
-  __ tst(input_reg, Operand(kSmiTagMask));
-  __ b(ne, deferred->entry());
-
-  // Smi to int32 conversion
-  __ SmiUntag(input_reg);  // Untag smi.
-
+  // Optimistically untag the input.
+  // If the input is a HeapObject, SmiUntag will set the carry flag.
+  __ SmiUntag(input_reg, SetCC);
+  // Branch to deferred code if the input was tagged.
+  // The deferred code will take care of restoring the tag.
+  __ b(cs, deferred->entry());
   __ bind(deferred->exit());
 }
 
 
 void LCodeGen::DoNumberUntagD(LNumberUntagD* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister());
   LOperand* result = instr->result();
   ASSERT(result->IsDoubleRegister());
 
@@ skipping 481 matching lines @@
   ASSERT(!environment->HasBeenRegistered());
   RegisterEnvironmentForDeoptimization(environment);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal