Changeset 281485 in webkit

Timestamp:

Aug 23, 2021, 7:59:56 PM (5 years ago)

Author:

sbarati@apple.com

Message:

Disable peephole optimizations in the byte code generator after rewriting instructions for for-in
​https://bugs.webkit.org/show_bug.cgi?id=229420
<rdar://82020528>

Reviewed by Keith Miller.

JSTests:

• stress/for-in-disable-bytecode-generator-peephole-optimizations-after-rewrite.js: Added.

(foo):

Source/JavaScriptCore:

The final instruction in a for-in loop might be the get by val that
we're rewriting because there was an escape. We won't ever actually
do peephole optimizations on this get_by_val today, but it breaks
some bookkeeping that the bytecode generator does. This patch makes
sure the bookkeeping is up to date.

• bytecompiler/BytecodeGenerator.cpp:

(JSC::ForInContext::finalize):

Location:

trunk

Files:

• JSTests/ChangeLog (modified) (1 diff)
• JSTests/stress/for-in-disable-bytecode-generator-peephole-optimizations-after-rewrite.js (added)
• Source/JavaScriptCore/ChangeLog (modified) (1 diff)
• Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp (modified) (3 diffs)

trunk/JSTests/ChangeLog

@@ +1 @@
+2021-08-23  Saam Barati  <sbarati@apple.com>
+
+        Disable peephole optimizations in the byte code generator after rewriting instructions for for-in
+        https://bugs.webkit.org/show_bug.cgi?id=229420
+        <rdar://82020528>
+
+        Reviewed by Keith Miller.
+
+        * stress/for-in-disable-bytecode-generator-peephole-optimizations-after-rewrite.js: Added.
+        (foo):
+
 2021-08-23  Saam Barati  <sbarati@apple.com>
 

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-08-23  Saam Barati  <sbarati@apple.com>
+
+        Disable peephole optimizations in the byte code generator after rewriting instructions for for-in
+        https://bugs.webkit.org/show_bug.cgi?id=229420
+        <rdar://82020528>
+
+        Reviewed by Keith Miller.
+
+        The final instruction in a for-in loop might be the get by val that
+        we're rewriting because there was an escape. We won't ever actually
+        do peephole optimizations on this get_by_val today, but it breaks
+        some bookkeeping that the bytecode generator does. This patch makes
+        sure the bookkeeping is up to date.
+
+        * bytecompiler/BytecodeGenerator.cpp:
+        (JSC::ForInContext::finalize):
+
 2021-08-23  Saam Barati  <sbarati@apple.com>
 

trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp

@@ -5370 +5370 @@
         return;
 
-    OpcodeID lastOpcodeID = generator.m_lastOpcodeID;
-    InstructionStream::MutableRef lastInstruction = generator.m_lastInstruction;
-
     for (const auto& instTuple : m_getInsts)
         rewriteOp<OpEnumeratorGetByVal, OpGetByVal>(generator, instTuple);
@@ -5391 +5388 @@
         generator.m_writer.seek(branchInstIndex);
 
-        generator.disablePeepholeOptimization();
-
         OpJmp::emit(&generator, BoundLabel(static_cast<int>(newBranchTarget) - static_cast<int>(branchInstIndex)));
 
@@ -5399 +5394 @@
     }
 
+    generator.disablePeepholeOptimization(); // We might've just changed the last bytecode that was emitted.
+
     generator.m_writer.seek(generator.m_writer.size());
-    if (generator.m_lastInstruction.offset() + generator.m_lastInstruction->size() != generator.m_writer.size()) {
-        generator.m_lastOpcodeID = lastOpcodeID;
-        generator.m_lastInstruction = lastInstruction;
-    }
 }