Skip some conditional deopts for Div/Mul when all uses are truncating

src/arm/lithium-codegen-arm.cc

 // Copyright 2012 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 1388 matching lines @@
         __ mul(scratch, result, ip);
         __ sub(remainder, dividend, scratch);
       }
   }
 }
 
 
 void LCodeGen::DoDivI(LDivI* instr) {
   if (instr->hydrogen()->HasPowerOf2Divisor()) {
     Register dividend = ToRegister(instr->left());
-    int32_t divisor =
-        HConstant::cast(instr->hydrogen()->right())->Integer32Value();
+    int32_t divisor = instr->hydrogen()->right()->GetInteger32Constant();
     int32_t test_value = 0;
     int32_t power = 0;
 
     if (divisor > 0) {
       test_value = divisor - 1;
       power = WhichPowerOf2(divisor);
     } else {
       // Check for (0 / -x) that will produce negative zero.
       if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
         __ tst(dividend, Operand(dividend));
         DeoptimizeIf(eq, instr->environment());
       }
       // Check for (kMinInt / -1).
       if (divisor == -1 && instr->hydrogen()->CheckFlag(HValue::kCanOverflow)) {
         __ cmp(dividend, Operand(kMinInt));
         DeoptimizeIf(eq, instr->environment());
       }
       test_value = - divisor - 1;
       power = WhichPowerOf2(-divisor);
     }
 
     if (test_value != 0) {
-      // Deoptimize if remainder is not 0.
-      __ tst(dividend, Operand(test_value));
-      DeoptimizeIf(ne, instr->environment());
-      __ mov(dividend, Operand(dividend, ASR, power));
+      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);
+        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));
+      }
     }
     if (divisor < 0) __ rsb(dividend, dividend, Operand(0));
 
     return;
   }
 
   const Register left = ToRegister(instr->left());
   const Register right = ToRegister(instr->right());
   const Register result = ToRegister(instr->result());
 
@@ skipping 20 matching lines @@
     __ b(ne, &left_not_min_int);
     __ cmp(right, Operand(-1));
     DeoptimizeIf(eq, instr->environment());
     __ bind(&left_not_min_int);
   }
 
   if (CpuFeatures::IsSupported(SUDIV)) {
     CpuFeatureScope scope(masm(), SUDIV);
     __ sdiv(result, left, right);
 
-    // Compute remainder and deopt if it's not zero.
-    const Register remainder = scratch0();
-    __ mls(remainder, result, right, left);
-    __ cmp(remainder, Operand::Zero());
-    DeoptimizeIf(ne, instr->environment());
+    if (!instr->hydrogen()->CheckFlag(
+        HInstruction::kAllUsesTruncatingToInt32)) {
+      // Compute remainder and deopt if it's not zero.
+      const Register remainder = scratch0();
+      __ mls(remainder, result, right, left);
+      __ cmp(remainder, Operand::Zero());
+      DeoptimizeIf(ne, instr->environment());
+    }
   } else {
     const DoubleRegister vleft = ToDoubleRegister(instr->temp());
     const DoubleRegister vright = double_scratch0();
     __ vmov(vleft.low(), left);
     __ vmov(vright.low(), right);
     __ vcvt_f64_s32(vleft, vleft.low());
     __ vcvt_f64_s32(vright, vright.low());
     __ vdiv(vleft, vleft, vright);  // vleft now contains the result.
-
-    // Convert back to integer32; deopt if exact conversion is not possible.
-    // Use vright as scratch register.
     __ vcvt_s32_f64(vright.low(), vleft);
     __ vmov(result, vright.low());
-    __ vcvt_f64_s32(vright, vright.low());
-    __ VFPCompareAndSetFlags(vleft, vright);
-    DeoptimizeIf(ne, instr->environment());
+
+    if (!instr->hydrogen()->CheckFlag(
+        HInstruction::kAllUsesTruncatingToInt32)) {
+      // Deopt if exact conversion to integer was not possible.
+      // Use vright as scratch register.
+      __ vcvt_f64_s32(vright, vright.low());
+      __ VFPCompareAndSetFlags(vleft, vright);
+      DeoptimizeIf(ne, instr->environment());
+    }
   }
 }
 
 
 void LCodeGen::DoMultiplyAddD(LMultiplyAddD* instr) {
   DwVfpRegister addend = ToDoubleRegister(instr->addend());
   DwVfpRegister multiplier = ToDoubleRegister(instr->multiplier());
   DwVfpRegister multiplicand = ToDoubleRegister(instr->multiplicand());
 
   // This is computed in-place.
@@ skipping 4359 matching lines @@
   __ sub(scratch, result, Operand::PointerOffsetFromSmiKey(index));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal