From b1ece42218dcd13de9e7f9f991a695e9f8cc0db0 Mon Sep 17 00:00:00 2001
From: kvn <unknown>
Date: Wed, 7 Sep 2011 12:58:42 -0700
Subject: [PATCH] 7054211: No loop unrolling done in jdk7b144 for a test
 update() while loop Summary: restore unrolling code for CaffeineMark.
 Reviewed-by: never

---
 src/share/vm/opto/loopTransform.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/share/vm/opto/loopTransform.cpp b/src/share/vm/opto/loopTransform.cpp
index 148c2e3d2..eee153a89 100644
--- a/src/share/vm/opto/loopTransform.cpp
+++ b/src/share/vm/opto/loopTransform.cpp
@@ -709,10 +709,13 @@ bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
 
   // Adjust body_size to determine if we unroll or not
   uint body_size = _body.size();
+  // Key test to unroll loop in CRC32 java code
+  int xors_in_loop = 0;
   // Also count ModL, DivL and MulL which expand mightly
   for (uint k = 0; k < _body.size(); k++) {
     Node* n = _body.at(k);
     switch (n->Opcode()) {
+      case Op_XorI: xors_in_loop++; break; // CRC32 java code
       case Op_ModL: body_size += 30; break;
       case Op_DivL: body_size += 30; break;
       case Op_MulL: body_size += 10; break;
@@ -729,7 +732,8 @@ bool IdealLoopTree::policy_unroll( PhaseIdealLoop *phase ) const {
 
   // Check for being too big
   if (body_size > (uint)LoopUnrollLimit) {
-     // Normal case: loop too big
+    if (xors_in_loop >= 4 && body_size < (uint)LoopUnrollLimit*4) return true;
+    // Normal case: loop too big
     return false;
   }
 
-- 
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