ART: Refactor SsaBuilder for more precise typing info

This patch refactors the SsaBuilder to do the following:

1) All phis are constructed live and marked dead if not used or proved
to be conflicting.

2) Primitive type propagation, now not a separate pass, identifies
conflicting types and marks corresponding phis dead.

3) When compiling --debuggable, DeadPhiHandling used to revive phis
which had only environmental uses but did not attempt to resolve
conflicts. This pass was removed as obsolete and is now superseded
by primitive type propagation (identifying conflicting phis) and
SsaDeadPhiEliminiation (keeping phis live if debuggable + env use).

4) Resolving conflicts requires correct primitive type information
on all instructions. This was not the case for ArrayGet instructions
which can have ambiguous types in the bytecode. To this end,
SsaBuilder now runs reference type propagation and types ArrayGets
from the type of the input array.

5) With RTP being run inside the SsaBuilder, it is not necessary to
run it as a separate optimization pass. Optimizations can now assume
that all instructions of type kPrimNot have reference type info after
SsaBuilder (with the exception of NullConstant).

6) Graph now contains a reference type to be assigned to NullConstant.
All reference type instructions therefore have RTI, as now enforced
by the SsaChecker.

Bug: 24252151
Bug: 24252100
Bug: 22538329
Bug: 25786318

Change-Id: I7a3aee1ff66c82d64b4846611c547af17e91d260

1 files changed, 7 insertions, 12 deletions

diff --git a/compiler/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index e9fdb84d1e..5f1328f545 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -30,6 +30,7 @@
 #include "optimization.h"
 #include "reference_type_propagation.h"
 #include "register_allocator.h"
+#include "ssa_builder.h"
 #include "ssa_liveness_analysis.h"
 #include "utils/assembler.h"
 
@@ -505,7 +506,7 @@ class HGraphVisualizerPrinter : public HGraphDelegateVisitor {
       } else {
         StartAttributeStream("loop") << "B" << info->GetHeader()->GetBlockId();
       }
-    } else if ((IsPass(ReferenceTypePropagation::kReferenceTypePropagationPassName)
+    } else if ((IsPass(SsaBuilder::kSsaBuilderPassName)
         || IsPass(HInliner::kInlinerPassName))
         && (instruction->GetType() == Primitive::kPrimNot)) {
       ReferenceTypeInfo info = instruction->IsLoadClass()
@@ -519,21 +520,15 @@ class HGraphVisualizerPrinter : public HGraphDelegateVisitor {
         StartAttributeStream("exact") << std::boolalpha << info.IsExact() << std::noboolalpha;
       } else if (instruction->IsLoadClass()) {
         StartAttributeStream("klass") << "unresolved";
-      } else if (instruction->IsNullConstant()) {
+      } else {
         // The NullConstant may be added to the graph during other passes that happen between
         // ReferenceTypePropagation and Inliner (e.g. InstructionSimplifier). If the inliner
         // doesn't run or doesn't inline anything, the NullConstant remains untyped.
         // So we should check NullConstants for validity only after reference type propagation.
-        //
-        // Note: The infrastructure to properly type NullConstants everywhere is to complex to add
-        // for the benefits.
-        StartAttributeStream("klass") << "not_set";
-        DCHECK(!is_after_pass_
-            || !IsPass(ReferenceTypePropagation::kReferenceTypePropagationPassName))
-            << " Expected a valid rti after reference type propagation";
-      } else {
-        DCHECK(!is_after_pass_)
-            << "Expected a valid rti after reference type propagation";
+        DCHECK(graph_in_bad_state_ ||
+               (!is_after_pass_ && IsPass(SsaBuilder::kSsaBuilderPassName)))
+            << instruction->DebugName() << instruction->GetId() << " has invalid rti "
+            << (is_after_pass_ ? "after" : "before") << " pass " << pass_name_;
       }
     }
     if (disasm_info_ != nullptr) {