ART: Remove incorrect HFakeString optimization

Simplification of HFakeString assumes that it cannot be used until
String.<init> is called which is not true and causes different
behaviour between the compiler and the interpreter. This patch
removes the optimization together with the HFakeString instruction.

Instead, HNewInstance is generated and an empty String allocated
until it is replaced with the result of the StringFactory call. This
is consistent with the behaviour of the interpreter but is too
conservative. A follow-up CL will attempt to optimize out the initial
allocation when possible.

Bug: 26457745
Bug: 26486014

Change-Id: I7139e37ed00a880715bfc234896a930fde670c44

1 files changed, 8 insertions, 7 deletions

diff --git a/compiler/optimizing/ssa_builder.h b/compiler/optimizing/ssa_builder.h
index 0fcc3a1306..efe0dff4ed 100644
--- a/compiler/optimizing/ssa_builder.h
+++ b/compiler/optimizing/ssa_builder.h
@@ -70,13 +70,14 @@ class SsaBuilder : public HGraphVisitor {
   ArenaVector<HInstruction*>* GetLocalsFor(HBasicBlock* block);
   HInstruction* ValueOfLocal(HBasicBlock* block, size_t local);
 
-  void VisitBasicBlock(HBasicBlock* block);
-  void VisitLoadLocal(HLoadLocal* load);
-  void VisitStoreLocal(HStoreLocal* store);
-  void VisitInstruction(HInstruction* instruction);
-  void VisitTemporary(HTemporary* instruction);
-  void VisitArrayGet(HArrayGet* aget);
-  void VisitArraySet(HArraySet* aset);
+  void VisitBasicBlock(HBasicBlock* block) OVERRIDE;
+  void VisitLoadLocal(HLoadLocal* load) OVERRIDE;
+  void VisitStoreLocal(HStoreLocal* store) OVERRIDE;
+  void VisitInstruction(HInstruction* instruction) OVERRIDE;
+  void VisitTemporary(HTemporary* instruction) OVERRIDE;
+  void VisitArrayGet(HArrayGet* aget) OVERRIDE;
+  void VisitArraySet(HArraySet* aset) OVERRIDE;
+  void VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) OVERRIDE;
 
   static constexpr const char* kSsaBuilderPassName = "ssa_builder";