Simplify ToBoolean if we know we have a Smi.

src/arm/codegen-arm.cc

 // Copyright 2010 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 730 matching lines @@
 }
 
 
 // ECMA-262, section 9.2, page 30: ToBoolean(). Convert the given
 // register to a boolean in the condition code register. The code
 // may jump to 'false_target' in case the register converts to 'false'.
 void CodeGenerator::ToBoolean(JumpTarget* true_target,
                               JumpTarget* false_target) {
   // Note: The generated code snippet does not change stack variables.
   //       Only the condition code should be set.
+  bool known_smi = frame_->KnownSmiAt(0);
   Register tos = frame_->PopToRegister();
 
   // Fast case checks
 
   // Check if the value is 'false'.
-  __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-  __ cmp(tos, ip);
-  false_target->Branch(eq);
+  if (!known_smi) {
+    __ LoadRoot(ip, Heap::kFalseValueRootIndex);
+    __ cmp(tos, ip);
+    false_target->Branch(eq);
 
-  // Check if the value is 'true'.
-  __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-  __ cmp(tos, ip);
-  true_target->Branch(eq);
+    // Check if the value is 'true'.
+    __ LoadRoot(ip, Heap::kTrueValueRootIndex);
+    __ cmp(tos, ip);
+    true_target->Branch(eq);
 
-  // Check if the value is 'undefined'.
-  __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-  __ cmp(tos, ip);
-  false_target->Branch(eq);
+    // Check if the value is 'undefined'.
+    __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
+    __ cmp(tos, ip);
+    false_target->Branch(eq);
+  }
 
   // Check if the value is a smi.
   __ cmp(tos, Operand(Smi::FromInt(0)));
-  false_target->Branch(eq);
-  __ tst(tos, Operand(kSmiTagMask));
-  true_target->Branch(eq);
 
-  // Slow case: call the runtime.
-  frame_->EmitPush(tos);
-  frame_->CallRuntime(Runtime::kToBool, 1);
-  // Convert the result (r0) to a condition code.
-  __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-  __ cmp(r0, ip);
+  if (!known_smi) {
+    false_target->Branch(eq);
+    __ tst(tos, Operand(kSmiTagMask));
+    true_target->Branch(eq);
+
+    // Slow case: call the runtime.
+    frame_->EmitPush(tos);
+    frame_->CallRuntime(Runtime::kToBool, 1);
+    // Convert the result (r0) to a condition code.
+    __ LoadRoot(ip, Heap::kFalseValueRootIndex);
+    __ cmp(r0, ip);
+  }
 
   cc_reg_ = ne;
 }
 
 
 void CodeGenerator::GenericBinaryOperation(Token::Value op,
                                            OverwriteMode overwrite_mode,
                                            GenerateInlineSmi inline_smi,
                                            int constant_rhs) {
   // top of virtual frame: y
@@ skipping 10374 matching lines @@
   __ bind(&string_add_runtime);
   __ TailCallRuntime(Runtime::kStringAdd, 2, 1);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM