RFR (S) 8217639: Minimal and Zero builds fail after JDK-8217519 (Improve RegMask population count calculation)

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8217639

Reason: New test references "extern uint8_t byte[] bitsInByte", and that is defined in
libadt/vectset.cpp, which is not compiled when C2 is disabled in Minimal and Zero VM builds. I was
first considering to enabled libadt build when C2 is disabled, but the more straight-forward fix
would be to give the test its own golden data to test against. This would also implicitly test for
accidental bugs in bitsInByte matrix in production code.

Fix:

diff -r c96f9aa1f3d8 -r 29037fc5194d test/hotspot/gtest/utilities/test_population_count.cpp
--- a/test/hotspot/gtest/utilities/test_population_count.cpp    Wed Jan 23 13:16:16 2019 +0000
+++ b/test/hotspot/gtest/utilities/test_population_count.cpp    Wed Jan 23 17:04:25 2019 +0100
@@ -29,18 +29,35 @@
 #include "utilities/globalDefinitions.hpp"
 #include "unittest.hpp"

+uint8_t test_popcnt_bitsInByte[BITS_IN_BYTE_ARRAY_SIZE] = {
+        0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
+        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+        4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
+};

 TEST(population_count, sparse) {
-  extern uint8_t bitsInByte[BITS_IN_BYTE_ARRAY_SIZE];
   // Step through the entire input range from a random starting point,
   // verify population_count return values against the lookup table
   // approach used historically
   uint32_t step = 4711;
   for (uint32_t value = os::random() % step; value < UINT_MAX - step; value += step) {
-    uint32_t lookup = bitsInByte[(value >> 24) & 0xff] +
-                      bitsInByte[(value >> 16) & 0xff] +
-                      bitsInByte[(value >> 8)  & 0xff] +
-                      bitsInByte[ value        & 0xff];
+    uint32_t lookup = test_popcnt_bitsInByte[(value >> 24) & 0xff] +
+                      test_popcnt_bitsInByte[(value >> 16) & 0xff] +
+                      test_popcnt_bitsInByte[(value >> 8)  & 0xff] +
+                      test_popcnt_bitsInByte[ value        & 0xff];

     EXPECT_EQ(lookup, population_count(value))
         << "value = " << value;

Testing: Linux x86_64 {server,zero,minimal} build and gtest:population_count

-Aleksey

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