Simplify the pair optimization. Rather than using complex type traits,

just ensure that the number of bytes in the pair is the sum of the bytes
in each side of the pair. As long as thats true, there are no extra
bytes that might be padding.

Also add a few tests that previously would have slipped through the
checking. The more accurate checking mechanism catches these and ensures
they are handled conservatively correctly.

Thanks to Duncan for prodding me to do this right and more simply.

llvm-svn: 151891

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/HashingTest.cpp b/llvm/unittests/ADT/HashingTest.cpp
index a12cf90e274..449b6afae23 100644
--- a/llvm/unittests/ADT/HashingTest.cpp
+++ b/llvm/unittests/ADT/HashingTest.cpp
@@ -42,6 +42,16 @@ using namespace llvm;
 
 namespace {
 
+struct NonPOD {
+  uint64_t x, y;
+  NonPOD(uint64_t x, uint64_t y) : x(x), y(y) {}
+  ~NonPOD() {}
+  friend hash_code hash_value(const NonPOD &obj) {
+    return hash_combine(obj.x, obj.y);
+  }
+};
+
+
 TEST(HashingTest, HashValueBasicTest) {
   int x = 42, y = 43, c = 'x';
   void *p = 0;
@@ -73,6 +83,16 @@ TEST(HashingTest, HashValueBasicTest) {
             hash_value(std::make_pair(42, std::make_pair(43, 44))));
   EXPECT_EQ(hash_value(std::make_pair(42, std::make_pair(43, 44))),
             hash_value(std::make_pair(std::make_pair(42, 43), 44)));
+
+  // Ensure that pairs which have padding bytes *inside* them don't get treated
+  // this way.
+  EXPECT_EQ(hash_combine('0', hash_combine(1ull, '2')),
+            hash_value(std::make_pair('0', std::make_pair(1ull, '2'))));
+
+  // Ensure that non-POD pairs don't explode the traits used.
+  NonPOD obj1(1, 2), obj2(3, 4), obj3(5, 6);
+  EXPECT_EQ(hash_combine(obj1, hash_combine(obj2, obj3)),
+            hash_value(std::make_pair(obj1, std::make_pair(obj2, obj3))));
 }
 
 template <typename T, size_t N> T *begin(T (&arr)[N]) { return arr; }