commit bae9c9ad631576966c82872b32e309dc720b309b
author Aart Bik <ajcbik@google.com> Mon Sep 11 14:51:54 2017 -0700
committer Aart Bik <ajcbik@google.com> Mon Sep 11 15:24:52 2017 -0700
tree 69704a78f1c5006d0e35e46df2095b4555885dce
parent 47d00f6c4657af33c3cc29783c0f2eb156aa1449

Fix bug in BCE remainder handling.

Rationale:
(1) code was looking up index in wrong block
(2) code was merging monotonic (rather than the other way around).
This
(a) caused DCHECK failure, reproduced and fixed with new test
(b) missed cases, reproduced and fixed with new test

Bug: 65551926

Test: test-art-host
Change-Id: I9991635bf8b04925b6929b73abf659717639a78b

compiler/optimizing/bounds_check_elimination.cc

diff --git a/compiler/optimizing/bounds_check_elimination.cc b/compiler/optimizing/bounds_check_elimination.cc
index 2f96cfa..6b832da 100644
--- a/compiler/optimizing/bounds_check_elimination.cc
+++ b/compiler/optimizing/bounds_check_elimination.cc
@@ -1143,9 +1143,9 @@
           ValueBound(nullptr, 1 - right_const),
           ValueBound(nullptr, right_const - 1));
 
-      ValueRange* left_range = LookupValueRange(left, left->GetBlock());
+      ValueRange* left_range = LookupValueRange(left, instruction->GetBlock());
       if (left_range != nullptr) {
-        right_range = left_range->Narrow(right_range);
+        right_range = right_range->Narrow(left_range);
       }
       AssignRange(instruction->GetBlock(), instruction, right_range);
       return;
@@ -1172,9 +1172,9 @@
           GetGraph()->GetArena(),
           lower,
           upper);
-      ValueRange* left_range = LookupValueRange(left, left->GetBlock());
+      ValueRange* left_range = LookupValueRange(left, instruction->GetBlock());
       if (left_range != nullptr) {
-        right_range = left_range->Narrow(right_range);
+        right_range = right_range->Narrow(left_range);
       }
       AssignRange(instruction->GetBlock(), instruction, right_range);
       return;

test/449-checker-bce/src/Main.java

diff --git a/test/449-checker-bce/src/Main.java b/test/449-checker-bce/src/Main.java
index f466eea..60e653c 100644
--- a/test/449-checker-bce/src/Main.java
+++ b/test/449-checker-bce/src/Main.java
@@ -962,6 +962,25 @@
     }
   }
 
+  /// CHECK-START: void Main.modArrayIndex5(int[], int) BCE (before)
+  /// CHECK-DAG: BoundsCheck
+  /// CHECK-DAG: ArraySet
+  //
+  /// CHECK-START: void Main.modArrayIndex5(int[], int) BCE (after)
+  /// CHECK-NOT: BoundsCheck
+  /// CHECK-DAG: ArraySet
+  public static void modArrayIndex5(int[] x, int i) {
+    while (true) {
+      int xi = i % x.length;
+      if (xi < 0)
+        break;
+      if (i >= x.length)
+        break;
+      x[xi] = i;
+      i++;
+    }
+  }
+
   /// CHECK-START: void Main.bubbleSort(int[]) GVN (before)
   /// CHECK: BoundsCheck
   /// CHECK: ArrayGet
@@ -1690,6 +1709,21 @@
 
     sieve(20);
 
+    int[] x1 = new int[10];
+    int[] x2 = new int[10];
+    int[] x3 = new int[10];
+    modArrayIndex5(x1, -1);
+    modArrayIndex5(x2, 0);
+    modArrayIndex5(x3, 5);
+    for (int i = 0; i < 10; i++) {
+      int e1 = 0;
+      int e2 = i;
+      int e3 = i < 5 ? 0 : i;
+      if (x1[i] != e1 || x2[i] != e2 || x3[i] != e3) {
+        System.out.println("modarray failed!");
+      }
+    }
+
     int[] array = {5, 2, 3, 7, 0, 1, 6, 4};
     bubbleSort(array);
     for (int i = 0; i < 8; i++) {