Do not use repeated subtractions in mod-i, it hurts performance in general.

src/ia32/lithium-codegen-ia32.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 1216 matching lines @@
     if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
       __ j(not_zero, &done, Label::kNear);
       DeoptimizeIf(no_condition, instr->environment());
     } else {
       __ jmp(&done, Label::kNear);
     }
     __ bind(&positive_dividend);
     __ and_(dividend, divisor - 1);
     __ bind(&done);
   } else {
-    Label done, remainder_eq_dividend, slow, do_subtraction, both_positive;
+    Label done, remainder_eq_dividend, slow, both_positive;
     Register left_reg = ToRegister(instr->left());
     Register right_reg = ToRegister(instr->right());
     Register result_reg = ToRegister(instr->result());
 
     ASSERT(left_reg.is(eax));
     ASSERT(result_reg.is(edx));
     ASSERT(!right_reg.is(eax));
     ASSERT(!right_reg.is(edx));
 
     // Check for x % 0.
@@ skipping 15 matching lines @@
     // If the dividend is smaller than the nonnegative
     // divisor, the dividend is the result.
     __ cmp(left_reg, Operand(right_reg));
     __ j(less, &remainder_eq_dividend, Label::kNear);
 
     // Check if the divisor is a PowerOfTwo integer.
     Register scratch = ToRegister(instr->temp());
     __ mov(scratch, right_reg);
     __ sub(Operand(scratch), Immediate(1));
     __ test(scratch, Operand(right_reg));
-    __ j(not_zero, &do_subtraction, Label::kNear);
+    __ j(not_zero, &slow, Label::kNear);
     __ and_(left_reg, Operand(scratch));
     __ jmp(&remainder_eq_dividend, Label::kNear);
 
-    __ bind(&do_subtraction);
-    const int kUnfolds = 3;
-    // Try a few subtractions of the dividend.
-    __ mov(scratch, left_reg);
-    for (int i = 0; i < kUnfolds; i++) {
-      // Reduce the dividend by the divisor.
-      __ sub(left_reg, Operand(right_reg));
-      // Check if the dividend is less than the divisor.
-      __ cmp(left_reg, Operand(right_reg));
-      __ j(less, &remainder_eq_dividend, Label::kNear);
-    }
-    __ mov(left_reg, scratch);
-
     // Slow case, using idiv instruction.
     __ bind(&slow);
 
     // Check for (kMinInt % -1).
     if (instr->hydrogen()->CheckFlag(HValue::kCanOverflow)) {
       Label left_not_min_int;
       __ cmp(left_reg, kMinInt);
       __ j(not_zero, &left_not_min_int, Label::kNear);
       __ cmp(right_reg, -1);
       DeoptimizeIf(zero, instr->environment());
@@ skipping 5353 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32