Inline integer modulo operation.

runtime/vm/intermediate_language_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 2221 matching lines @@
       summary->set_in(1, Location::Constant(right_constant->value()));
       summary->AddTemp(Location::RequiresRegister());
     } else {
       summary->set_in(1, Location::RequiresRegister());
       summary->AddTemp(Location::RequiresRegister());
       summary->AddTemp(Location::RequiresFpuRegister());
     }
     summary->set_out(Location::RequiresRegister());
     return summary;
   }
+  if (op_kind() == Token::kMOD) {
+    summary->set_in(0, Location::RequiresRegister());
+    summary->set_in(1, Location::RequiresRegister());
+    summary->AddTemp(Location::RequiresRegister());
+    summary->AddTemp(Location::RequiresFpuRegister());
+    summary->set_out(Location::RequiresRegister());
+    return summary;
+  }
   summary->set_in(0, Location::RequiresRegister());
   summary->set_in(1, Location::RegisterOrSmiConstant(right()));
   if (((op_kind() == Token::kSHL) && !is_truncating()) ||
       (op_kind() == Token::kSHR)) {
     summary->AddTemp(Location::RequiresRegister());
   }
   // We make use of 3-operand instructions by not requiring result register
   // to be identical to first input register as on Intel.
   summary->set_out(Location::RequiresRegister());
   return summary;
@@ skipping 208 matching lines @@
 
       __ IntegerDivide(result, temp, IP, dtemp, DTMP);
 
       // Check the corner case of dividing the 'MIN_SMI' with -1, in which
       // case we cannot tag the result.
       __ CompareImmediate(result, 0x40000000);
       __ b(deopt, EQ);
       __ SmiTag(result);
       break;
     }
+    case Token::kMOD: {
+      // Handle divide by zero in runtime.
+      __ cmp(right, ShifterOperand(0));
+      __ b(deopt, EQ);
+      Register temp = locs()->temp(0).reg();
+      DRegister dtemp = EvenDRegisterOf(locs()->temp(1).fpu_reg());
+      __ Asr(temp, left, kSmiTagSize);  // SmiUntag left into temp.
+      __ Asr(IP, right, kSmiTagSize);  // SmiUntag right into IP.
+
+      __ IntegerDivide(result, temp, IP, dtemp, DTMP);
+
+      __ Asr(IP, right, kSmiTagSize);  // SmiUntag right into IP.

[zra, 2013/11/07 16:40:06]

IntegerDivide doesn't clobber temp and IP here, so you could reuse them, but
maybe it's safer to reload in case IntegerDivide changes. Another option is to
add a comment to IntegerDivide stating the integer register inputs must be
preserved.

[srdjan, 2013/11/07 21:26:10]

I think it is safe to assume that IP is not guaranteed to be preserved across
compound assembly instructions. The cost is minimal, compared to cost of
division, I think.

+      __ mls(result, IP, result, temp);  // result <- left - right * result
+      __ SmiTag(result);
+      //  res = left % right;
+      //  if (res < 0) {
+      //    if (right < 0) {
+      //      res = res - right;
+      //    } else {
+      //      res = res + right;
+      //    }
+      //  }
+      Label done;
+      __ cmp(result, ShifterOperand(0));
+      __ b(&done, GE);
+      // Result is negative, adjust it.
+      __ cmp(right, ShifterOperand(0));
+      __ sub(result, result, ShifterOperand(right), LT);
+      __ add(result, result, ShifterOperand(right), GE);
+      __ Bind(&done);
+      break;
+    }
     case Token::kSHR: {
       if (CanDeoptimize()) {
         __ CompareImmediate(right, 0);
         __ b(deopt, LT);
       }
       __ Asr(IP, right, kSmiTagSize);  // SmiUntag right into IP.
       // sarl operation masks the count to 5 bits.
       const intptr_t kCountLimit = 0x1F;
       Range* right_range = this->right()->definition()->range();
       if ((right_range == NULL) ||
           !right_range->IsWithin(RangeBoundary::kMinusInfinity, kCountLimit)) {
         __ CompareImmediate(IP, kCountLimit);
         __ LoadImmediate(IP, kCountLimit, GT);
       }
       Register temp = locs()->temp(0).reg();
       __ Asr(temp, left, kSmiTagSize);  // SmiUntag left into temp.
       __ Asr(result, temp, IP);
       __ SmiTag(result);
       break;
     }
     case Token::kDIV: {
       // Dispatches to 'Double./'.
       // TODO(srdjan): Implement as conversion to double and double division.
       UNREACHABLE();
       break;
     }
-    case Token::kMOD: {
-      // TODO(srdjan): Implement.
-      UNREACHABLE();
-      break;
-    }
     case Token::kOR:
     case Token::kAND: {
       // Flow graph builder has dissected this operation to guarantee correct
       // behavior (short-circuit evaluation).
       UNREACHABLE();
       break;
     }
     default:
       UNREACHABLE();
       break;
@@ skipping 2067 matching lines @@
   compiler->GenerateCall(token_pos(),
                          &label,
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM