Use stack locations instead of register for binary Smi operations when possible.

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
===================================================================
--- runtime/vm/intermediate_language_ia32.cc	(revision 23244)
+++ runtime/vm/intermediate_language_ia32.cc	(working copy)
@@ -2312,7 +2312,12 @@
     LocationSummary* summary =
         new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
     summary->set_in(0, Location::RequiresRegister());
-    summary->set_in(1, Location::RegisterOrSmiConstant(right()));
+    ConstantInstr* constant = right()->definition()->AsConstant();
+    if (constant != NULL) {
+      summary->set_in(1, Location::RegisterOrSmiConstant(right()));
+    } else {
+      summary->set_in(1, Location::Any());

[Florian Schneider, 2013/05/28 10:09:37]

We also have Location::PrefersRegister() as an alternative. The difference is
that if there is a free register and the value is spilled, it will go into the
free register. If all registers are occupied, it will be on the stack.

I think PrefersRegister() would be better than Any(), but it should be confirmed
with a measurement.

[srdjan, 2013/05/28 10:39:01]

Changed to PrefersRegister, no significant difference in performance observed.

+    }
     summary->set_out(Location::SameAsFirstInput());
     return summary;
   }
@@ -2433,8 +2438,49 @@
         break;
     }
     return;
-  }
+  }  // if locs()->in(1).IsConstant()
 
+  if (locs()->in(1).IsStackSlot()) {
+    const Address& right = locs()->in(1).ToStackSlotAddress();
+    switch (op_kind()) {
+      case Token::kADD: {
+        __ addl(left, right);
+        if (deopt != NULL) __ j(OVERFLOW, deopt);
+        break;
+      }
+      case Token::kSUB: {
+        __ subl(left, right);
+        if (deopt != NULL) __ j(OVERFLOW, deopt);
+        break;
+      }
+      case Token::kMUL: {
+        __ SmiUntag(left);
+        __ imull(left, right);
+        if (deopt != NULL) __ j(OVERFLOW, deopt);
+        break;
+      }
+      case Token::kBIT_AND: {
+        // No overflow check.
+        __ andl(left, right);
+        break;
+      }
+      case Token::kBIT_OR: {
+        // No overflow check.
+        __ orl(left, right);
+        break;
+      }
+      case Token::kBIT_XOR: {
+        // No overflow check.
+        __ xorl(left, right);
+        break;
+      }
+      default:
+        UNREACHABLE();
+    }
+    return;
+  }  // if locs()->in(1).IsStackSlot.
+
+  // if locs()->in(1).IsRegister.
   Register right = locs()->in(1).reg();
   switch (op_kind()) {
     case Token::kADD: {