Remove duplicates phis created during SSA transformation

When creating equivalent phis we copy the inputs of the original phi
which may be improperly typed. This will be fixed during the type
propagation but as a result we may have two equivalent phis with the
same type for the same dex register. This is correct but generates more
code and prevent some optimizations.

This CL adds another step in the SSA builder to remove the extra Phi
nodes created due to equality operators.

The graph checker verifies that for a given dex register not two phis
have the same type.

Also, replace zero int constant with null constant when we compare a
reference against null.

Change-Id: Id37cc11a016ea767c7e351575e003d822a9d2e60

1 files changed, 22 insertions, 24 deletions

diff --git a/compiler/optimizing/graph_checker.cc b/compiler/optimizing/graph_checker.cc
index 7c3c2bf03d..e4dc534dff 100644
--- a/compiler/optimizing/graph_checker.cc
+++ b/compiler/optimizing/graph_checker.cc
@@ -18,6 +18,7 @@
 
 #include <map>
 #include <string>
+#include <sstream>
 
 #include "base/bit_vector-inl.h"
 #include "base/stringprintf.h"
@@ -194,6 +195,17 @@ void SSAChecker::VisitBasicBlock(HBasicBlock* block) {
     }
   }
 
+  // Check Phi uniqueness (no two Phis with the same type refer to the same register).
+  for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
+    HPhi* phi = it.Current()->AsPhi();
+    if (phi->GetNextEquivalentPhiWithSameType() != nullptr) {
+      std::stringstream type_str;
+      type_str << phi->GetType();
+      AddError(StringPrintf("Equivalent phi (%d) found for VReg %d with type: %s",
+          phi->GetId(), phi->GetRegNumber(), type_str.str().c_str()));
+    }
+  }
+
   if (block->IsLoopHeader()) {
     CheckLoop(block);
   }
@@ -399,37 +411,23 @@ void SSAChecker::VisitCondition(HCondition* op) {
   }
   HInstruction* lhs = op->InputAt(0);
   HInstruction* rhs = op->InputAt(1);
-  if (lhs->GetType() == Primitive::kPrimNot) {
-    if (!op->IsEqual() && !op->IsNotEqual()) {
+  if (PrimitiveKind(lhs->GetType()) != PrimitiveKind(rhs->GetType())) {
+    AddError(StringPrintf(
+        "Condition %s %d has inputs of different types: %s, and %s.",
+        op->DebugName(), op->GetId(),
+        Primitive::PrettyDescriptor(lhs->GetType()),
+        Primitive::PrettyDescriptor(rhs->GetType())));
+  }
+  if (!op->IsEqual() && !op->IsNotEqual()) {
+    if ((lhs->GetType() == Primitive::kPrimNot)) {
       AddError(StringPrintf(
           "Condition %s %d uses an object as left-hand side input.",
           op->DebugName(), op->GetId()));
-    }
-    if (rhs->IsIntConstant() && rhs->AsIntConstant()->GetValue() != 0) {
-      AddError(StringPrintf(
-          "Condition %s %d compares an object with a non-zero integer: %d.",
-          op->DebugName(), op->GetId(),
-          rhs->AsIntConstant()->GetValue()));
-    }
-  } else if (rhs->GetType() == Primitive::kPrimNot) {
-    if (!op->IsEqual() && !op->IsNotEqual()) {
+    } else if (rhs->GetType() == Primitive::kPrimNot) {
       AddError(StringPrintf(
           "Condition %s %d uses an object as right-hand side input.",
           op->DebugName(), op->GetId()));
     }
-    if (lhs->IsIntConstant() && lhs->AsIntConstant()->GetValue() != 0) {
-      AddError(StringPrintf(
-          "Condition %s %d compares a non-zero integer with an object: %d.",
-          op->DebugName(), op->GetId(),
-          lhs->AsIntConstant()->GetValue()));
-    }
-  } else if (PrimitiveKind(lhs->GetType()) != PrimitiveKind(rhs->GetType())) {
-      AddError(StringPrintf(
-          "Condition %s %d has inputs of different types: "
-          "%s, and %s.",
-          op->DebugName(), op->GetId(),
-          Primitive::PrettyDescriptor(lhs->GetType()),
-          Primitive::PrettyDescriptor(rhs->GetType())));
   }
 }