ARM: Implement fast code for ModI.

src/arm/lithium-codegen-arm.cc

 // Copyright 2011 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 1021 matching lines @@
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     Label ok;
     __ tst(left, Operand(left));
     __ b(ne, &ok);
     __ tst(right, Operand(right));
     __ b(pl, &ok);
     __ b(al, &deoptimize);
     __ bind(&ok);
   }
 
+  // Try a few common cases before using the generic stub.
+  Label call_stub;
+  const int kUnfolds = 3;
+  // Skip if either side is negative.
+  __ cmp(left, Operand(0));
+  __ cmp(right, Operand(0), NegateCondition(mi));
+  __ b(mi, &call_stub);
+  // If the right hand side is smaller than the (nonnegative)
+  // left hand side, it is the result. Else try a few subtractions
+  // of the left hand side.
+  __ mov(scratch, left);
+  for (int i = 0; i < kUnfolds; i++) {
+    // Check if the left hand side is less or equal than the
+    // the right hand side.
+    __ cmp(scratch, right);
+    __ mov(result, scratch, LeaveCC, lt);
+    __ b(lt, &done);
+    // If not, reduce the left hand side by the right hand
+    // side and check again.
+    if (i < kUnfolds - 1) __ sub(scratch, scratch, right);
+  }
+
+  // Check for power of two on the right hand side.
+  __ sub(scratch, right, Operand(1), SetCC);
+  __ b(mi, &call_stub);
+  __ tst(scratch, right);
+  __ b(ne, &call_stub);
+  // Perform modulo operation.
+  __ and_(result, scratch, Operand(left));
+
+  __ bind(&call_stub);
   // Call the generic stub. The numbers in r0 and r1 have
   // to be tagged to Smis. If that is not possible, deoptimize.
   DeferredModI* deferred = new DeferredModI(this, instr);
   __ TrySmiTag(left, &deoptimize, scratch);
   __ TrySmiTag(right, &deoptimize, scratch);
 
   __ b(al, deferred->entry());
   __ bind(deferred->exit());
 
   // If the result in r0 is a Smi, untag it, else deoptimize.
   __ BranchOnNotSmi(result, &deoptimize);
-  __ mov(result, Operand(result, ASR, 1));
+  __ SmiUntag(result);
 
   __ b(al, &done);
   __ bind(&deoptimize);
   DeoptimizeIf(al, instr->environment());
   __ bind(&done);
 }
 
 
 void LCodeGen::DoDivI(LDivI* instr) {
   class DeferredDivI: public LDeferredCode {
@@ skipping 2300 matching lines @@
 
 
 void LCodeGen::DoOsrEntry(LOsrEntry* instr) {
   Abort("DoOsrEntry unimplemented.");
 }
 
 
 #undef __
 
 } }  // namespace v8::internal