Avoid redundant smi check for Math.abs

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/21180004

Patch from Weiliang Lin <weiliang.lin2@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16021 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-codegen-arm.cc

@@ -3765,7 +3765,7 @@ void LCodeGen::DoMathAbs(LMathAbs* instr) {
     DwVfpRegister input = ToDoubleRegister(instr->value());
     DwVfpRegister result = ToDoubleRegister(instr->result());
     __ vabs(result, input);
-  } else if (r.IsInteger32()) {
+  } else if (r.IsSmiOrInteger32()) {
     EmitIntegerMathAbs(instr);
   } else {
     // Representation is tagged.

src/ia32/lithium-codegen-ia32.cc

@@ -3821,7 +3821,7 @@ void LCodeGen::DoMathAbs(LMathAbs* instr) {
     __ xorps(scratch, scratch);
     __ subsd(scratch, input_reg);
     __ pand(input_reg, scratch);
-  } else if (r.IsInteger32()) {
+  } else if (r.IsSmiOrInteger32()) {
     EmitIntegerMathAbs(instr);
   } else {  // Tagged case.
     DeferredMathAbsTaggedHeapNumber* deferred =

src/x64/lithium-codegen-x64.cc

@@ -3426,6 +3426,17 @@ void LCodeGen::EmitIntegerMathAbs(LMathAbs* instr) {
 }
 
 
+void LCodeGen::EmitInteger64MathAbs(LMathAbs* instr) {
+  Register input_reg = ToRegister(instr->value());
+  __ testq(input_reg, input_reg);
+  Label is_positive;
+  __ j(not_sign, &is_positive, Label::kNear);
+  __ neg(input_reg);  // Sets flags.
+  DeoptimizeIf(negative, instr->environment());
+  __ bind(&is_positive);
+}
+
+
 void LCodeGen::DoMathAbs(LMathAbs* instr) {
   // Class for deferred case.
   class DeferredMathAbsTaggedHeapNumber: public LDeferredCode {
@@ -3451,6 +3462,8 @@ void LCodeGen::DoMathAbs(LMathAbs* instr) {
     __ andpd(input_reg, scratch);
   } else if (r.IsInteger32()) {
     EmitIntegerMathAbs(instr);
+  } else if (r.IsSmi()) {
+    EmitInteger64MathAbs(instr);
   } else {  // Tagged case.
     DeferredMathAbsTaggedHeapNumber* deferred =
         new(zone()) DeferredMathAbsTaggedHeapNumber(this, instr);

src/x64/lithium-codegen-x64.h

@@ -268,6 +268,7 @@ class LCodeGen BASE_EMBEDDED {
       uint32_t additional_index = 0);
 
   void EmitIntegerMathAbs(LMathAbs* instr);
+  void EmitInteger64MathAbs(LMathAbs* instr);
 
   // Support for recording safepoint and position information.
   void RecordSafepoint(LPointerMap* pointers,

test/mjsunit/math-abs.js

@@ -109,3 +109,14 @@ for(var i = 0; i < 1000; i++) {
 assertEquals(42, foo(-42));
 %OptimizeFunctionOnNextCall(foo)
 assertEquals(42, foo(-42));
+
+// Regression test for SMI input of Math.abs on X64, see:
+// https://codereview.chromium.org/21180004/
+var a = [-1, -2];
+function foo2() {
+  return Math.abs(a[0]);
+}
+assertEquals(1, foo2());
+assertEquals(1, foo2());
+%OptimizeFunctionOnNextCall(foo2);
+assertEquals(1, foo2());