# HG changeset patch
# User Josef Eisl <josef.eisl@jku.at>
# Date 1437575107 -7200
# Node ID de0d452a3520b3ae190d11139050547cb784e7ea
# Parent  d56555c627acd7e7ed70df1a7c4982457a6c1017
LinearScanWalker: fall back to usages with MustHaveRegister priority in #splitForSpilling.

diff -r d56555c627ac -r de0d452a3520 graal/com.oracle.graal.lir/src/com/oracle/graal/lir/alloc/lsra/LinearScanWalker.java
--- a/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/alloc/lsra/LinearScanWalker.java	Tue Jul 21 16:55:09 2015 +0200
+++ b/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/alloc/lsra/LinearScanWalker.java	Wed Jul 22 16:25:07 2015 +0200
@@ -485,7 +485,16 @@
     void splitForSpilling(Interval interval) {
         // calculate allowed range of splitting position
         int maxSplitPos = currentPosition;
-        int minSplitPos = Math.max(interval.previousUsage(RegisterPriority.ShouldHaveRegister, maxSplitPos) + 1, interval.from());
+        int previousUsage = interval.previousUsage(RegisterPriority.ShouldHaveRegister, maxSplitPos);
+        if (previousUsage == currentPosition) {
+            /*
+             * If there is a usage with ShouldHaveRegister priority at the current position fall
+             * back to MustHaveRegister priority. This only happens if register priority was
+             * downgraded to MustHaveRegister in #allocLockedRegister.
+             */
+            previousUsage = interval.previousUsage(RegisterPriority.MustHaveRegister, maxSplitPos);
+        }
+        int minSplitPos = Math.max(previousUsage + 1, interval.from());
 
         try (Indent indent = Debug.logAndIndent("splitting and spilling interval %s between %d and %d", interval, minSplitPos, maxSplitPos)) {