8334629: [BACKOUT] PhaseIdealLoop::conditional_move is too conservative

Reviewed-by: chagedorn, qamai
Backport-of: 933eaba

Author: TobiHartmann

src/hotspot/share/opto/loopopts.cpp

@@ -795,18 +795,25 @@ Node *PhaseIdealLoop::conditional_move( Node *region ) {
   // Avoid duplicated float compare.
   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
 
-  // Ignore cost if CMOVE can be moved outside the loop.
-  if (used_inside_loop && cost >= ConditionalMoveLimit) {
-    return nullptr;
+  float infrequent_prob = PROB_UNLIKELY_MAG(3);
+  // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
+  if (used_inside_loop) {
+    if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
+
+    // BlockLayoutByFrequency optimization moves infrequent branch
+    // from hot path. No point in CMOV'ing in such case (110 is used
+    // instead of 100 to take into account not exactness of float value).
+    if (BlockLayoutByFrequency) {
+      infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
+    }
   }
   // Check for highly predictable branch.  No point in CMOV'ing if
   // we are going to predict accurately all the time.
-  constexpr float infrequent_prob = PROB_UNLIKELY_MAG(2);
   if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
     //keep going
-  } else if (iff->_prob < infrequent_prob || iff->_prob > (1.0f - infrequent_prob)) {
+  } else if (iff->_prob < infrequent_prob ||
+      iff->_prob > (1.0f - infrequent_prob))
     return nullptr;
-  }
 
   // --------------
   // Now replace all Phis with CMOV's

test/hotspot/jtreg/ProblemList.txt

@@ -67,6 +67,7 @@ compiler/c2/Test8004741.java 8235801 generic-all
 compiler/c2/TestMergeStores.java#id0 8331311 generic-ppc64,linux-s390x
 compiler/c2/TestMergeStores.java#id1 8331311 generic-ppc64,linux-s390x
 compiler/c2/irTests/TestDuplicateBackedge.java 8318904 generic-all
+compiler/c2/irTests/TestIfMinMax.java 8334816 generic-all
 
 compiler/codecache/jmx/PoolsIndependenceTest.java 8264632 macosx-all
 compiler/codecache/CheckLargePages.java 8332654 linux-x64