From e652cc3b6f01551ea19193f884814a5a9a7b82b0 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Mon, 14 Jan 2019 09:41:26 +0700
Subject: [PATCH] DFA: support of arithmetic no-ops (*1, /1, >>0, etc.)

---
 .../dataFlow/value/DfaBinOpValue.java         | 10 +++++++
 .../dataFlow/fixture/ArithmeticNoOp.java      | 27 +++++++++++++++++++
 .../DataFlowRangeAnalysisTest.java            |  1 +
 3 files changed, 38 insertions(+)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/ArithmeticNoOp.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaBinOpValue.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaBinOpValue.java
index 18a4762c144a..9e9a4a471496 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaBinOpValue.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaBinOpValue.java
@@ -95,6 +95,16 @@ public class DfaBinOpValue extends DfaValue {
       }
       LongRangeSet leftRange = state.getValueFact(left, DfaFactType.RANGE);
       LongRangeSet rightRange = state.getValueFact(right, DfaFactType.RANGE);
+      if (tokenType.equals(JavaTokenType.ASTERISK)) {
+        if (LongRangeSet.point(1).equals(leftRange)) return right;
+        if (LongRangeSet.point(1).equals(rightRange)) return left;
+      }
+      if (tokenType.equals(JavaTokenType.DIV)) {
+        if (LongRangeSet.point(1).equals(rightRange)) return left;
+      }
+      if (tokenType.equals(JavaTokenType.GTGT) || tokenType.equals(JavaTokenType.LTLT) || tokenType.equals(JavaTokenType.GTGTGT)) {
+        if (LongRangeSet.point(0).equals(rightRange)) return left;
+      }
       if (leftRange != null && rightRange != null) {
         LongRangeSet result = leftRange.binOpFromToken(tokenType, rightRange, isLong);
         return myFactory.getFactValue(DfaFactType.RANGE, result);
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/ArithmeticNoOp.java b/java/java-tests/testData/inspection/dataFlow/fixture/ArithmeticNoOp.java
new file mode 100644
index 000000000000..b47f94a27111
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/ArithmeticNoOp.java
@@ -0,0 +1,27 @@
+import java.util.*;
+
+public class ArithmeticNoOp {
+  void test(long x, int y) {
+    if(y == 1) {
+      long z = x * y;
+      long t = x / y;
+      long u = y / z;
+      long w = y * z;
+      if (<warning descr="Condition 'z == x' is always 'true'">z == x</warning>) {}
+      if (<warning descr="Condition 't == x' is always 'true'">t == x</warning>) {}
+      if (<warning descr="Condition 'w == x' is always 'true'">w == x</warning>) {}
+      if (u == x) {}
+    }
+    if(y == 0) {
+      long a = x >> y;
+      long b = x << y;
+      long c = x >>> y;
+      long d = y >>> x;
+      if (<warning descr="Condition 'a == x' is always 'true'">a == x</warning>) {}
+      if (<warning descr="Condition 'b == x' is always 'true'">b == x</warning>) {}
+      if (<warning descr="Condition 'c == x' is always 'true'">c == x</warning>) {}
+      if (d == x) {}
+      if (<warning descr="Condition 'd == y' is always 'true'">d == y</warning>) {}
+    }
+  }
+}
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowRangeAnalysisTest.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowRangeAnalysisTest.java
index 640ade8ae1fb..6b9b93268f1b 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowRangeAnalysisTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowRangeAnalysisTest.java
@@ -60,4 +60,5 @@ public class DataFlowRangeAnalysisTest extends DataFlowInspectionTestCase {
   public void testTwoArraysDiff() { doTest(); }
   public void testModRange() { doTest(); }
   public void testBackPropagationMod() { doTest(); }
+  public void testArithmeticNoOp() { doTest(); }
 }