VM: More compact code for pushing constant arguments on ia32/x64.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index b58e4d1b41aacce57bb8ca650a796d9a875a462d..487d96194f51929571d9947e52acd8fc50429e86 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -238,14 +238,16 @@ LocationSummary* ConstantInstr::MakeLocationSummary(Zone* zone,
   const intptr_t kNumInputs = 0;
   return LocationSummary::Make(zone,
                                kNumInputs,
-                               Location::RequiresRegister(),
+                               Assembler::IsSafe(value())
+                                   ? Location::Constant(this)
+                                   : Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
 void ConstantInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // The register allocator drops constant definitions that have no uses.
-  if (!locs()->out(0).IsInvalid()) {
+  if (locs()->out(0).IsRegister()) {
     Register result = locs()->out(0).reg();
     __ LoadObject(result, value());
   }