Use GPRs for mints

runtime/vm/locations.h

Index: runtime/vm/locations.h
diff --git a/runtime/vm/locations.h b/runtime/vm/locations.h
index cabb8dbda12a8b5c01da1d51aa4d9cbe84202408..0a99d9fcfa71bfe0fc7db59f09cdc22be50ea436 100644
--- a/runtime/vm/locations.h
+++ b/runtime/vm/locations.h
@@ -365,6 +365,8 @@ class Location : public ValueObject {
     return KindField::decode(value_);
   }
 
+  Location Copy() const;
+
  private:
   explicit Location(uword value) : value_(value) { }
 
@@ -428,15 +430,20 @@ class PairLocation : public ZoneAllocated {
 
 class RegisterSet : public ValueObject {
  public:
-  RegisterSet() : cpu_registers_(0), fpu_registers_(0) {
+  RegisterSet() : cpu_registers_(0), untagged_cpu_registers_(0),
+                  fpu_registers_(0) {
     ASSERT(kNumberOfCpuRegisters <= (kWordSize * kBitsPerByte));
     ASSERT(kNumberOfFpuRegisters <= (kWordSize * kBitsPerByte));
   }
 
 
-  void Add(Location loc) {
+  void Add(Location loc, Representation rep = kTagged) {
     if (loc.IsRegister()) {
       cpu_registers_ |= (1 << loc.reg());
+      if (rep != kTagged) {
+        // CPU register contains an untagged value.
+        MarkUntagged(loc);
+      }
     } else if (loc.IsFpuRegister()) {
       fpu_registers_ |= (1 << loc.fpu_reg());
     }
@@ -450,6 +457,15 @@ class RegisterSet : public ValueObject {
     }
   }
 
+  void MarkUntagged(Location loc) {
+    ASSERT(loc.IsRegister());
+    untagged_cpu_registers_ |= (1 << loc.reg());
+  }
+
+  bool IsTagged(Register reg) const {
+    return (untagged_cpu_registers_ & (1 << reg)) == 0;
+  }
+
   bool ContainsRegister(Register reg) const {
     return (cpu_registers_ & (1 << reg)) != 0;
   }
@@ -468,6 +484,7 @@ class RegisterSet : public ValueObject {
 
  private:
   intptr_t cpu_registers_;
+  intptr_t untagged_cpu_registers_;
   intptr_t fpu_registers_;
 
   DISALLOW_COPY_AND_ASSIGN(RegisterSet);
@@ -561,6 +578,10 @@ class LocationSummary : public ZoneAllocated {
     return contains_call_ != kNoCall;
   }
 
+  bool HasCallOnSlowPath() {
+    return can_call() && !always_calls();
+  }
+
   void PrintTo(BufferFormatter* f) const;
 
   static LocationSummary* Make(intptr_t input_count,