Title: [281319] trunk/Source/_javascript_Core
- Revision
- 281319
- Author
- mark....@apple.com
- Date
- 2021-08-20 09:21:35 -0700 (Fri, 20 Aug 2021)
Log Message
Reduce StructureID entropy bits to 5 to make room for more StructureIDs.
https://bugs.webkit.org/show_bug.cgi?id=229326
rdar://60141624
Reviewed by Yusuke Suzuki.
* runtime/StructureIDTable.h:
Modified Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (281318 => 281319)
--- trunk/Source/_javascript_Core/ChangeLog 2021-08-20 15:56:05 UTC (rev 281318)
+++ trunk/Source/_javascript_Core/ChangeLog 2021-08-20 16:21:35 UTC (rev 281319)
@@ -1,3 +1,13 @@
+2021-08-20 Mark Lam <mark....@apple.com>
+
+ Reduce StructureID entropy bits to 5 to make room for more StructureIDs.
+ https://bugs.webkit.org/show_bug.cgi?id=229326
+ rdar://60141624
+
+ Reviewed by Yusuke Suzuki.
+
+ * runtime/StructureIDTable.h:
+
2021-08-19 Tim Nguyen <n...@apple.com>
Implement ::backdrop pseudo element
Modified: trunk/Source/_javascript_Core/runtime/StructureIDTable.h (281318 => 281319)
--- trunk/Source/_javascript_Core/runtime/StructureIDTable.h 2021-08-20 15:56:05 UTC (rev 281318)
+++ trunk/Source/_javascript_Core/runtime/StructureIDTable.h 2021-08-20 16:21:35 UTC (rev 281319)
@@ -140,7 +140,7 @@
// 1. StructureID is encoded as:
//
// ----------------------------------------------------------------
- // | 1 Nuke Bit | 24 StructureIDTable index bits | 7 entropy bits |
+ // | 1 Nuke Bit | 26 StructureIDTable index bits | 5 entropy bits |
// ----------------------------------------------------------------
//
// The entropy bits are chosen at random and assigned when a StructureID
@@ -149,15 +149,15 @@
// 2. For each StructureID, the StructureIDTable stores encodedStructureBits
// which are encoded from the structure pointer as such:
//
- // -----------------------------------------------------------------
- // | 9 low index bits | 7 entropy bits | 48 structure pointer bits |
- // -----------------------------------------------------------------
+ // ------------------------------------------------------------------
+ // | 11 low index bits | 5 entropy bits | 48 structure pointer bits |
+ // ------------------------------------------------------------------
//
- // The entropy bits here are the same 7 bits used in the encoding of the
+ // The entropy bits here are the same 5 bits used in the encoding of the
// StructureID for this structure entry in the StructureIDTable.
static constexpr uint32_t s_numberOfNukeBits = 1;
- static constexpr uint32_t s_numberOfEntropyBits = 7;
+ static constexpr uint32_t s_numberOfEntropyBits = 5;
static constexpr uint32_t s_entropyBitsShiftForStructurePointer = (sizeof(EncodedStructureBits) * 8) - 16;
static constexpr uint32_t s_maximumNumberOfStructures = 1 << (32 - s_numberOfEntropyBits - s_numberOfNukeBits);
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