ARM: Tweak the integer division operation.

BUG=none
TEST=test/mjsunit/lithium/DivI.js
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23536045

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16727 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1373,9 +1373,8 @@ LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
     if (instr->HasPowerOf2Divisor()) {
       ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
       LOperand* value = UseRegisterAtStart(instr->left());
-      LDivI* div =
-          new(zone()) LDivI(value, UseOrConstant(instr->right()), NULL);
-      return AssignEnvironment(DefineSameAsFirst(div));
+      LDivI* div = new(zone()) LDivI(value, UseConstant(instr->right()), NULL);
+      return AssignEnvironment(DefineAsRegister(div));
     }
     LOperand* dividend = UseRegister(instr->left());
     LOperand* divisor = UseRegister(instr->right());

src/arm/lithium-codegen-arm.cc

@@ -1383,7 +1383,8 @@ void LCodeGen::EmitSignedIntegerDivisionByConstant(
 
 void LCodeGen::DoDivI(LDivI* instr) {
   if (instr->hydrogen()->HasPowerOf2Divisor()) {
-    Register dividend = ToRegister(instr->left());
+    const Register dividend = ToRegister(instr->left());
+    const Register result = ToRegister(instr->result());
     int32_t divisor = instr->hydrogen()->right()->GetInteger32Constant();
     int32_t test_value = 0;
     int32_t power = 0;
@@ -1394,7 +1395,7 @@ void LCodeGen::DoDivI(LDivI* instr) {
     } else {
       // Check for (0 / -x) that will produce negative zero.
       if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-        __ tst(dividend, Operand(dividend));
+        __ cmp(dividend, Operand::Zero());
         DeoptimizeIf(eq, instr->environment());
       }
       // Check for (kMinInt / -1).
@@ -1409,20 +1410,26 @@ void LCodeGen::DoDivI(LDivI* instr) {
     if (test_value != 0) {
       if (instr->hydrogen()->CheckFlag(
           HInstruction::kAllUsesTruncatingToInt32)) {
-        __ cmp(dividend, Operand(0));
-        __ rsb(dividend, dividend, Operand(0), LeaveCC, lt);
-        __ mov(dividend, Operand(dividend, ASR, power));
-        if (divisor > 0) __ rsb(dividend, dividend, Operand(0), LeaveCC, lt);
-        if (divisor < 0) __ rsb(dividend, dividend, Operand(0), LeaveCC, gt);
+        __ sub(result, dividend, Operand::Zero(), SetCC);
+        __ rsb(result, result, Operand::Zero(), LeaveCC, lt);
+        __ mov(result, Operand(result, ASR, power));
+        if (divisor > 0) __ rsb(result, result, Operand::Zero(), LeaveCC, lt);
+        if (divisor < 0) __ rsb(result, result, Operand::Zero(), LeaveCC, gt);
         return;  // Don't fall through to "__ rsb" below.
       } else {
         // Deoptimize if remainder is not 0.
         __ tst(dividend, Operand(test_value));
         DeoptimizeIf(ne, instr->environment());
-        __ mov(dividend, Operand(dividend, ASR, power));
+        __ mov(result, Operand(dividend, ASR, power));
+        if (divisor < 0) __ rsb(result, result, Operand(0));
+      }
+    } else {
+      if (divisor < 0) {
+        __ rsb(result, dividend, Operand(0));
+      } else {
+        __ Move(result, dividend);
       }
     }
-    if (divisor < 0) __ rsb(dividend, dividend, Operand(0));
 
     return;
   }
@@ -1439,12 +1446,15 @@ void LCodeGen::DoDivI(LDivI* instr) {
 
   // Check for (0 / -x) that will produce negative zero.
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-    Label left_not_zero;
+    Label positive;
+    if (!instr->hydrogen()->CheckFlag(HValue::kCanBeDivByZero)) {
+      // Do the test only if it hadn't be done above.
+      __ cmp(right, Operand::Zero());
+    }
+    __ b(pl, &positive);
     __ cmp(left, Operand::Zero());
-    __ b(ne, &left_not_zero);
-    __ cmp(right, Operand::Zero());
-    DeoptimizeIf(mi, instr->environment());
-    __ bind(&left_not_zero);
+    DeoptimizeIf(eq, instr->environment());
+    __ bind(&positive);
   }
 
   // Check for (kMinInt / -1).

test/mjsunit/lithium/DivI.js

+// Copyright 2013 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax --no-use-osr
+
+function foo(a, b) {
+  var result = a / 35;
+  result += 50 / b;
+  result += a / b;
+  result += a / -1;
+  result += a / 1;
+  result += a / 4;
+  result += a / -4;
+  return result / b;
+}
+
+foo(700, 5);
+var r1 = foo(700, 5);
+%OptimizeFunctionOnNextCall(foo);
+var r2 = foo(700, 5);
+
+assertEquals(r1, r2);
+
+function boo(value) {
+  return value / -1;
+}
+
+// Test deoptimization of MinInt / -1.
+assertEquals(2147483600, boo(-2147483600));
+assertEquals(2147483600, boo(-2147483600));
+%OptimizeFunctionOnNextCall(boo);
+assertEquals(2147483600, boo(-2147483600));
+assertEquals(2147483648, boo(-2147483648));