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changeset 16114:a0d1dfc113b8

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Better documentation for HotSpotReferenceMap.
author Roland Schatz <roland.schatz@oracle.com>
date Mon, 16 Jun 2014 19:38:05 +0200
parents a3a9d703c078
children 9a595d3f9a2f
files graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Architecture.java graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Register.java graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotReferenceMap.java graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotTargetDescription.java
diffstat 4 files changed, 56 insertions(+), 42 deletions(-) [+]
line wrap: on
line diff
--- a/graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Architecture.java	Mon Jun 16 23:07:45 2014 +0200
+++ b/graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Architecture.java	Mon Jun 16 19:38:05 2014 +0200
@@ -34,11 +34,11 @@
 public abstract class Architecture {
 
     /**
-     * The number of bits required in a bit map covering all the registers that may store
-     * references. The bit position of a register in the map is the register's
-     * {@linkplain Register#number number}.
+     * The number of entries required in a {@link ReferenceMap} covering all the registers that may
+     * store references. The index of a register in the reference map is given by
+     * {@link Register#getReferenceMapIndex()}.
      */
-    private final int registerReferenceMapBitCount;
+    private final int registerReferenceMapSize;
 
     /**
      * Represents the natural size of words (typically registers and pointers) of this architecture,
@@ -85,7 +85,7 @@
     private final int returnAddressSize;
 
     protected Architecture(String name, int wordSize, ByteOrder byteOrder, boolean unalignedMemoryAccess, Register[] registers, int implicitMemoryBarriers, int nativeCallDisplacementOffset,
-                    int registerReferenceMapBitCount, int returnAddressSize) {
+                    int registerReferenceMapSize, int returnAddressSize) {
         this.name = name;
         this.registers = registers;
         this.wordSize = wordSize;
@@ -93,13 +93,13 @@
         this.unalignedMemoryAccess = unalignedMemoryAccess;
         this.implicitMemoryBarriers = implicitMemoryBarriers;
         this.machineCodeCallDisplacementOffset = nativeCallDisplacementOffset;
-        this.registerReferenceMapBitCount = registerReferenceMapBitCount;
+        this.registerReferenceMapSize = registerReferenceMapSize;
         this.returnAddressSize = returnAddressSize;
     }
 
     /**
      * Converts this architecture to a string.
-     * 
+     *
      * @return the string representation of this architecture
      */
     @Override
@@ -107,8 +107,8 @@
         return getName().toLowerCase();
     }
 
-    public int getRegisterReferenceMapBitCount() {
-        return registerReferenceMapBitCount;
+    public int getRegisterReferenceMapSize() {
+        return registerReferenceMapSize;
     }
 
     /**
@@ -163,7 +163,7 @@
     /**
      * Determines the barriers in a given barrier mask that are explicitly required on this
      * architecture.
-     * 
+     *
      * @param barriers a mask of the barrier constants
      * @return the value of {@code barriers} minus the barriers unnecessary on this architecture
      */
@@ -173,9 +173,9 @@
 
     /**
      * Gets the size in bytes of the specified kind for this target.
-     * 
+     *
      * @param kind the kind for which to get the size
-     * 
+     *
      * @return the size in bytes of {@code kind}
      */
     public int getSizeInBytes(PlatformKind kind) {
@@ -205,7 +205,7 @@
 
     /**
      * Determine whether a kind can be stored in a register of a given category.
-     * 
+     *
      * @param category the category of the register
      * @param kind the kind that should be stored in the register
      */
@@ -213,7 +213,7 @@
 
     /**
      * Return the largest kind that can be stored in a register of a given category.
-     * 
+     *
      * @param category the category of the register
      * @return the largest kind that can be stored in a register {@code category}
      */
--- a/graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Register.java	Mon Jun 16 23:07:45 2014 +0200
+++ b/graal/com.oracle.graal.api.code/src/com/oracle/graal/api/code/Register.java	Mon Jun 16 19:38:05 2014 +0200
@@ -137,6 +137,9 @@
         return registerCategory;
     }
 
+    /**
+     * Get the start index of this register in the {@link ReferenceMap}.
+     */
     public int getReferenceMapIndex() {
         return (encoding << registerCategory.referenceMapShift) + registerCategory.referenceMapOffset;
     }
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotReferenceMap.java	Mon Jun 16 23:07:45 2014 +0200
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotReferenceMap.java	Mon Jun 16 19:38:05 2014 +0200
@@ -34,25 +34,36 @@
 
     private static final long serialVersionUID = -1052183095979496819L;
 
+    private static final int BITS_PER_WORD = 3;
+
     /**
-     * Contains 3 bits per 64 bit register, and n*3 bits per n*64 bit vector register.
-     * <ul>
-     * <li>bit0 = 0: contains no references</li>
-     * <li>bit0 = 1, bit1+2 = 0: contains a wide oop</li>
-     * <li>bit0 = 1, bit1 = 1: contains a narrow oop in the lower 32 bit</li>
-     * <li>bit0 = 1, bit2 = 1: contains a narrow oop in the upper 32 bit</li>
-     * </ul>
+     * Contains 3 bits per scalar register, and n*3 bits per n-word vector register (e.g., on a
+     * 64-bit system, a 256-bit vector register requires 12 reference map bits).
+     * <p>
+     * These bits can have the following values (LSB first):
+     *
+     * <pre>
+     * 000 - contains no references
+     * 100 - contains a wide oop
+     * 110 - contains a narrow oop in the lower half
+     * 101 - contains a narrow oop in the upper half
+     * 111 - contains two narrow oops
+     * </pre>
      */
     private final BitSet registerRefMap;
 
     /**
-     * Contains 3 bits per stack slot.
-     * <ul>
-     * <li>bit0 = 0: contains no references</li>
-     * <li>bit0 = 1, bit1+2 = 0: contains a wide oop</li>
-     * <li>bit0 = 1, bit1 = 1: contains a narrow oop in the lower half</li>
-     * <li>bit0 = 1, bit2 = 1: contains a narrow oop in the upper half</li>
-     * </ul>
+     * Contains 3 bits per stack word.
+     * <p>
+     * These bits can have the following values (LSB first):
+     *
+     * <pre>
+     * 000 - contains no references
+     * 100 - contains a wide oop
+     * 110 - contains a narrow oop in the lower half
+     * 101 - contains a narrow oop in the upper half
+     * 111 - contains two narrow oops
+     * </pre>
      */
     private final BitSet frameRefMap;
 
@@ -60,18 +71,18 @@
 
     public HotSpotReferenceMap(int registerCount, int frameSlotCount, TargetDescription target) {
         if (registerCount > 0) {
-            this.registerRefMap = new BitSet(registerCount * 3);
+            this.registerRefMap = new BitSet(registerCount * BITS_PER_WORD);
         } else {
             this.registerRefMap = null;
         }
-        this.frameRefMap = new BitSet(frameSlotCount * 3);
+        this.frameRefMap = new BitSet(frameSlotCount * BITS_PER_WORD);
         this.target = target;
     }
 
     private static void setOop(BitSet map, int startIdx, LIRKind kind) {
         int length = kind.getPlatformKind().getVectorLength();
-        map.clear(3 * startIdx, 3 * (startIdx + length) - 1);
-        for (int i = 0, idx = 3 * startIdx; i < length; i++, idx += 3) {
+        map.clear(BITS_PER_WORD * startIdx, BITS_PER_WORD * (startIdx + length) - 1);
+        for (int i = 0, idx = BITS_PER_WORD * startIdx; i < length; i++, idx += BITS_PER_WORD) {
             if (kind.isReference(i)) {
                 map.set(idx);
             }
@@ -81,8 +92,8 @@
     private static void setNarrowOop(BitSet map, int idx, LIRKind kind) {
         int length = kind.getPlatformKind().getVectorLength();
         int nextIdx = idx + (length + 1) / 2;
-        map.clear(3 * idx, 3 * nextIdx - 1);
-        for (int i = 0, regIdx = 3 * idx; i < length; i += 2, regIdx += 3) {
+        map.clear(BITS_PER_WORD * idx, BITS_PER_WORD * nextIdx - 1);
+        for (int i = 0, regIdx = BITS_PER_WORD * idx; i < length; i += 2, regIdx += BITS_PER_WORD) {
             if (kind.isReference(i)) {
                 map.set(regIdx);
                 map.set(regIdx + 1);
@@ -130,11 +141,11 @@
                 // so setNarrowOop won't work correctly
                 int idx = offset / target.wordSize;
                 if (kind.isReference(0)) {
-                    frameRefMap.set(3 * idx);
+                    frameRefMap.set(BITS_PER_WORD * idx);
                     if (offset % target.wordSize == 0) {
-                        frameRefMap.set(3 * idx + 1);
+                        frameRefMap.set(BITS_PER_WORD * idx + 1);
                     } else {
-                        frameRefMap.set(3 * idx + 2);
+                        frameRefMap.set(BITS_PER_WORD * idx + 2);
                     }
                 }
             }
@@ -152,14 +163,14 @@
     }
 
     public void appendRegisterMap(StringBuilder sb, RefMapFormatter formatter) {
-        for (int reg = registerRefMap.nextSetBit(0); reg >= 0; reg = registerRefMap.nextSetBit(reg + 2)) {
-            sb.append(' ').append(formatter.formatRegister(reg / 2));
+        for (int reg = registerRefMap.nextSetBit(0); reg >= 0; reg = registerRefMap.nextSetBit(reg + BITS_PER_WORD)) {
+            sb.append(' ').append(formatter.formatRegister(reg / BITS_PER_WORD));
         }
     }
 
     public void appendFrameMap(StringBuilder sb, RefMapFormatter formatter) {
-        for (int slot = frameRefMap.nextSetBit(0); slot >= 0; slot = frameRefMap.nextSetBit(slot + 3)) {
-            sb.append(' ').append(formatter.formatStackSlot(slot / 3));
+        for (int slot = frameRefMap.nextSetBit(0); slot >= 0; slot = frameRefMap.nextSetBit(slot + BITS_PER_WORD)) {
+            sb.append(' ').append(formatter.formatStackSlot(slot / BITS_PER_WORD));
         }
     }
 }
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotTargetDescription.java	Mon Jun 16 23:07:45 2014 +0200
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotTargetDescription.java	Mon Jun 16 19:38:05 2014 +0200
@@ -46,6 +46,6 @@
 
     @Override
     public ReferenceMap createReferenceMap(boolean hasRegisters, int stackSlotCount) {
-        return new HotSpotReferenceMap(hasRegisters ? arch.getRegisterReferenceMapBitCount() : 0, stackSlotCount, this);
+        return new HotSpotReferenceMap(hasRegisters ? arch.getRegisterReferenceMapSize() : 0, stackSlotCount, this);
     }
 }