ART: Fix the simplifier for add/sub

Instruction simplifier for add/sub should not proceed with floats
because that might cause the incorrect behavior with signed zero.

Change-Id: If0c9bf3931bcbf96b0814f8605a86997aea37145
Signed-off-by: Serguei Katkov <serguei.i.katkov@intel.com>

1 files changed, 16 insertions, 8 deletions

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index d3911456fb..931a1c3cb7 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -438,9 +438,14 @@ void InstructionSimplifierVisitor::VisitAdd(HAdd* instruction) {
     //    ADD dst, src, 0
     // with
     //    src
-    instruction->ReplaceWith(input_other);
-    instruction->GetBlock()->RemoveInstruction(instruction);
-    return;
+    // Note that we cannot optimize `x + 0.0` to `x` for floating-point. When
+    // `x` is `-0.0`, the former expression yields `0.0`, while the later
+    // yields `-0.0`.
+    if (Primitive::IsIntegralType(instruction->GetType())) {
+      instruction->ReplaceWith(input_other);
+      instruction->GetBlock()->RemoveInstruction(instruction);
+      return;
+    }
   }
 
   HInstruction* left = instruction->GetLeft();
@@ -800,21 +805,24 @@ void InstructionSimplifierVisitor::VisitSub(HSub* instruction) {
   HConstant* input_cst = instruction->GetConstantRight();
   HInstruction* input_other = instruction->GetLeastConstantLeft();
 
+  Primitive::Type type = instruction->GetType();
+  if (Primitive::IsFloatingPointType(type)) {
+    return;
+  }
+
   if ((input_cst != nullptr) && input_cst->IsZero()) {
     // Replace code looking like
     //    SUB dst, src, 0
     // with
     //    src
+    // Note that we cannot optimize `x - 0.0` to `x` for floating-point. When
+    // `x` is `-0.0`, the former expression yields `0.0`, while the later
+    // yields `-0.0`.
     instruction->ReplaceWith(input_other);
     instruction->GetBlock()->RemoveInstruction(instruction);
     return;
   }
 
-  Primitive::Type type = instruction->GetType();
-  if (!Primitive::IsIntegralType(type)) {
-    return;
-  }
-
   HBasicBlock* block = instruction->GetBlock();
   ArenaAllocator* allocator = GetGraph()->GetArena();