Quick: Fix and enable DCE and improve GVN/DCE cleanup.

When eliminating a move by renaming its source register,
check that it doesn't conflict with vreg usage by insns
between the defining insn and the move.

Improve the GVN/DCE cleanup so that it can handle cases
where GVN or DCE is individually disabled in the pass driver
but not in the disable_opt flags.

Bug: 19419671
Change-Id: I49bb67b81509f51fbaf90c6016c509962be43736
diff --git a/compiler/dex/gvn_dead_code_elimination_test.cc b/compiler/dex/gvn_dead_code_elimination_test.cc
index 4d2b8b3..3eb372c 100644
--- a/compiler/dex/gvn_dead_code_elimination_test.cc
+++ b/compiler/dex/gvn_dead_code_elimination_test.cc
@@ -1030,6 +1030,40 @@
   }
 }
 
+TEST_F(GvnDeadCodeEliminationTestSimple, NoRename4) {
+  static const MIRDef mirs[] = {
+      DEF_CONST(3, Instruction::CONST, 0u, 1000u),
+      DEF_UNIQUE_REF(3, Instruction::NEW_INSTANCE, 1u),
+      DEF_CONST(3, Instruction::CONST, 2u, 100u),
+      DEF_CONST(3, Instruction::CONST, 3u, 200u),
+      DEF_BINOP(3, Instruction::OR_INT_2ADDR, 4u, 2u, 3u),   // 3. Find definition of the move src.
+      DEF_MOVE(3, Instruction::MOVE, 5u, 0u),                // 4. Uses move dest vreg.
+      DEF_MOVE(3, Instruction::MOVE, 6u, 4u),                // 2. Find overwritten move src.
+      DEF_CONST(3, Instruction::CONST, 7u, 2000u),           // 1. Overwrites 4u, look for moves.
+  };
+
+  static const int32_t sreg_to_vreg_map[] = { 0, 1, 2, 3, 2, 4, 0, 2 };
+  PrepareSRegToVRegMap(sreg_to_vreg_map);
+
+  PrepareMIRs(mirs);
+  PerformGVN_DCE();
+
+  ASSERT_EQ(arraysize(mirs), value_names_.size());
+  static const size_t diff_indexes[] = { 0, 1, 2, 3, 4, 7 };
+  ExpectValueNamesNE(diff_indexes);
+  EXPECT_EQ(value_names_[0], value_names_[5]);
+  EXPECT_EQ(value_names_[4], value_names_[6]);
+
+  static const bool eliminated[] = {
+      false, false, false, false, false, false, false, false
+  };
+  static_assert(arraysize(eliminated) == arraysize(mirs), "array size mismatch");
+  for (size_t i = 0; i != arraysize(eliminated); ++i) {
+    bool actually_eliminated = (static_cast<int>(mirs_[i].dalvikInsn.opcode) == kMirOpNop);
+    EXPECT_EQ(eliminated[i], actually_eliminated) << i;
+  }
+}
+
 TEST_F(GvnDeadCodeEliminationTestSimple, Simple1) {
   static const IFieldDef ifields[] = {
       { 0u, 1u, 0u, false, kDexMemAccessObject },