Mul simplification should expect zero operand

It is possible that zero constant can appear due to
simplification of other instructions, so we cannot expect
zero handling from constant optimizations.

Change-Id: I084126fd0c106ac2683c4f10a451960d9807f4f6
Signed-off-by: Serguei Katkov <serguei.i.katkov@intel.com>

4 files changed, 41 insertions, 3 deletions

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 98c0eedeb2..225af77a19 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -427,9 +427,16 @@ void InstructionSimplifierVisitor::VisitMul(HMul* instruction) {
 
   if (Primitive::IsIntOrLongType(type)) {
     int64_t factor = Int64FromConstant(input_cst);
-    // We expect the `0` case to have been handled in the constant folding pass.
-    DCHECK_NE(factor, 0);
-    if (IsPowerOfTwo(factor)) {
+    // Even though constant propagation also takes care of the zero case, other
+    // optimizations can lead to having a zero multiplication.
+    if (factor == 0) {
+      // Replace code looking like
+      //    MUL dst, src, 0
+      // with
+      //    0
+      instruction->ReplaceWith(input_cst);
+      instruction->GetBlock()->RemoveInstruction(instruction);
+    } else if (IsPowerOfTwo(factor)) {
       // Replace code looking like
       //    MUL dst, src, pow_of_2
       // with
diff --git a/test/475-simplify-mul-zero/expected.txt b/test/475-simplify-mul-zero/expected.txt
new file mode 100644
index 0000000000..7ed6ff82de
--- /dev/null
+++ b/test/475-simplify-mul-zero/expected.txt
@@ -0,0 +1 @@
+5
diff --git a/test/475-simplify-mul-zero/info.txt b/test/475-simplify-mul-zero/info.txt
new file mode 100644
index 0000000000..0db11f2823
--- /dev/null
+++ b/test/475-simplify-mul-zero/info.txt
@@ -0,0 +1,2 @@
+Regression check for optimizing simplify instruction pass.
+Mul should expect zero constant as input.
\ No newline at end of file
diff --git a/test/475-simplify-mul-zero/src/Main.java b/test/475-simplify-mul-zero/src/Main.java
new file mode 100644
index 0000000000..57adcff01e
--- /dev/null
+++ b/test/475-simplify-mul-zero/src/Main.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+public class Main {
+  public static void main(String[] args) {
+    long l3 = 2207693990L;
+    int i12 = 5;
+
+    for (int i = 1; i < 2; ++i) {
+        i12 ^= (int)(-((-(-(l3 - l3))) * i));
+    }
+
+    System.out.println(i12);
+  }
+}