From 53a41ac9305f3c435cbb975d773bbdb5490d8321 Mon Sep 17 00:00:00 2001
From: Vladimir Marko <vmarko@google.com>
Date: Thu, 31 Jan 2019 10:31:09 +0000
Subject: ART: Fix off-by-one error in BCE.

Bug: 123284765
Test: Additional test in 622-checker-bce-regressions
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: Ic231434aacc9dba0ccd664a3f4b7b5d8c665ae2a
---
 compiler/optimizing/bounds_check_elimination.cc |  6 ++++--
 test/622-checker-bce-regressions/src/Main.java  | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/compiler/optimizing/bounds_check_elimination.cc b/compiler/optimizing/bounds_check_elimination.cc
index 54a1ae9f9e..e35d50220e 100644
--- a/compiler/optimizing/bounds_check_elimination.cc
+++ b/compiler/optimizing/bounds_check_elimination.cc
@@ -845,8 +845,10 @@ class BCEVisitor : public HGraphVisitor {
           // make one more attempt to get a constant in the array range.
           ValueRange* existing_range = LookupValueRange(array_length, block);
           if (existing_range != nullptr &&
-              existing_range->IsConstantValueRange()) {
-            ValueRange constant_array_range(&allocator_, lower, existing_range->GetLower());
+              existing_range->IsConstantValueRange() &&
+              existing_range->GetLower().GetConstant() > 0) {
+            ValueBound constant_upper(nullptr, existing_range->GetLower().GetConstant() - 1);
+            ValueRange constant_array_range(&allocator_, lower, constant_upper);
             if (index_range->FitsIn(&constant_array_range)) {
               ReplaceInstruction(bounds_check, index);
               return;
diff --git a/test/622-checker-bce-regressions/src/Main.java b/test/622-checker-bce-regressions/src/Main.java
index 6ba2644b97..595ade8ff6 100644
--- a/test/622-checker-bce-regressions/src/Main.java
+++ b/test/622-checker-bce-regressions/src/Main.java
@@ -42,8 +42,22 @@ public class Main {
     return j;
   }
 
+  static public void $noinline$regressionTest123284765(String str) {
+    try {
+      int l = str.length();
+      if (l == 34) {
+        str.charAt(l);
+        fail();
+      }
+    } catch (StringIndexOutOfBoundsException expected) {
+      expectEquals(34, str.length());
+    }
+  }
+
   public static void main(String[] args) {
     expectEquals(8, doNotVisitAfterForwardBCE(array));
+    $noinline$regressionTest123284765("0123456789012345678901234567890123");
+    $noinline$regressionTest123284765("012345678901");
     System.out.println("passed");
   }
 
@@ -52,4 +66,8 @@ public class Main {
       throw new Error("Expected: " + expected + ", found: " + result);
     }
   }
+
+  private static void fail() {
+    throw new Error("FAIL");
+  }
 }
-- 
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