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changeset 19034:94ca6ce786ee

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StackSlotAllocation: improve javadoc.
author Josef Eisl <josef.eisl@jku.at>
date Thu, 29 Jan 2015 10:38:01 +0100
parents 74b144f7c54a
children 9a3bde73e05a
files graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/LSStackSlotAllocator.java
diffstat 1 files changed, 12 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/LSStackSlotAllocator.java	Wed Jan 28 19:32:47 2015 +0100
+++ b/graal/com.oracle.graal.lir/src/com/oracle/graal/lir/stackslotalloc/LSStackSlotAllocator.java	Thu Jan 29 10:38:01 2015 +0100
@@ -41,8 +41,15 @@
 
 /**
  * Linear Scan {@link StackSlotAllocator}.
+ * <p>
+ * <b>Remark:</b> The analysis works under the assumption that a stack slot is no longer live after
+ * its last usage. If an {@link LIRInstruction instruction} transfers the raw address of the stack
+ * slot to another location, e.g. a registers, and this location is referenced later on, the
+ * {@link com.oracle.graal.lir.LIRInstruction.Use usage} of the stack slot must be marked with the
+ * {@link OperandFlag#UNINITIALIZED}. Otherwise the stack slot might be reused and its content
+ * destroyed.
  */
-public class LSStackSlotAllocator implements StackSlotAllocator {
+public final class LSStackSlotAllocator implements StackSlotAllocator {
 
     public static class Options {
         // @formatter:off
@@ -107,7 +114,10 @@
             new SlowIntervalBuilder().build();
         }
 
-        private class SlowIntervalBuilder {
+        /**
+         * Calculates the stack intervals using a worklist-based backwards data-flow analysis.
+         */
+        private final class SlowIntervalBuilder {
             final BlockMap<BitSet> liveInMap;
             final BlockMap<BitSet> liveOutMap;