# HG changeset patch
# User roland
# Date 1461002247 -10800
# Node ID f8383064eaa286347eb491290a9c660a6ffdae1b
# Parent  808cbf1958ce8dcd3b33a44c2967d29b0e4c2a6a
8154135: Loop alignment may be added inside the loop body
Reviewed-by: kvn, vlivanov

diff -r 808cbf1958ce -r f8383064eaa2 hotspot/src/share/vm/opto/block.cpp
--- a/hotspot/src/share/vm/opto/block.cpp	Mon Apr 18 11:22:51 2016 +0200
+++ b/hotspot/src/share/vm/opto/block.cpp	Mon Apr 18 20:57:27 2016 +0300
@@ -73,7 +73,7 @@
 }
 #endif
 
-uint Block::code_alignment() {
+uint Block::code_alignment() const {
   // Check for Root block
   if (_pre_order == 0) return CodeEntryAlignment;
   // Check for Start block
@@ -1727,8 +1727,14 @@
     first_block()->set_loop_alignment(targ_block);
 
   } else {
-    // Backbranch into the middle of a trace
-    targ_block->set_loop_alignment(targ_block);
+    // That loop may already have a loop top (we're reaching it again
+    // through the backedge of an outer loop)
+    Block* b = prev(targ_block);
+    bool has_top = targ_block->head()->is_Loop() && b->has_loop_alignment() && !b->head()->is_Loop();
+    if (!has_top) {
+      // Backbranch into the middle of a trace
+      targ_block->set_loop_alignment(targ_block);
+    }
   }
 
   return loop_rotated;
diff -r 808cbf1958ce -r f8383064eaa2 hotspot/src/share/vm/opto/block.hpp
--- a/hotspot/src/share/vm/opto/block.hpp	Mon Apr 18 11:22:51 2016 +0200
+++ b/hotspot/src/share/vm/opto/block.hpp	Mon Apr 18 20:57:27 2016 +0300
@@ -197,7 +197,7 @@
 
   // Report the alignment required by this block.  Must be a power of 2.
   // The previous block will insert nops to get this alignment.
-  uint code_alignment();
+  uint code_alignment() const;
   uint compute_loop_alignment();
 
   // BLOCK_FREQUENCY is a sentinel to mark uses of constant block frequencies.
diff -r 808cbf1958ce -r f8383064eaa2 hotspot/src/share/vm/opto/c2_globals.hpp
--- a/hotspot/src/share/vm/opto/c2_globals.hpp	Mon Apr 18 11:22:51 2016 +0200
+++ b/hotspot/src/share/vm/opto/c2_globals.hpp	Mon Apr 18 20:57:27 2016 +0300
@@ -587,7 +587,7 @@
           range(0, 100)                                                     \
                                                                             \
   product(bool, BlockLayoutRotateLoops, true,                               \
-          "Allow back branches to be fall throughs in the block layour")    \
+          "Allow back branches to be fall throughs in the block layout")    \
                                                                             \
   develop(bool, InlineReflectionGetCallerClass, true,                       \
           "inline sun.reflect.Reflection.getCallerClass(), known to be "    \