Changeset 277758 in webkit for trunk/Source/JavaScriptCore/jit/JIT.cpp

Timestamp:

May 19, 2021, 3:30:16 PM (4 years ago)

Author:

[email protected]

Message:

Ripping out broken Baseline JIT rare case profiling.
​https://bugs.webkit.org/show_bug.cgi?id=225983

Reviewed by Saam Barati and Robin Morisset.

The profiling has been broken in recent times. Fixing it to work does not appear
to improve performance. Ripping out the profiling appears to not hurt performance.
However, ripping out the profiling appears to save on code size generated for the
Baseline JIT.

Base New Diff

BaselineJIT: 73299112 (69.903481 MB) 65910128 (62.856796 MB) 0.90x (reduction)

DFG: 36850540 (35.143414 MB) 36374400 (34.689331 MB) 0.99x

Thunk: 23128652 (22.057201 MB) 22892292 (21.831791 MB) 0.99x

InlineCache: 22210972 (21.182034 MB) 22083508 (21.060474 MB) 0.99x

FTL: 6065064 (5.784096 MB) 6128080 (5.844193 MB) 1.01x

Wasm: 2305124 (2.198338 MB) 2309732 (2.202732 MB) 1.00x

YarrJIT: 1522712 (1.452171 MB) 1536104 (1.464943 MB) 1.01x

CSSJIT: 0 0

Uncategorized: 0 0

Cumulative diff since the start of this effort to put more code in JIT thunks:

Base New Diff

BaselineJIT: 89089964 (84.962811 MB) 65910128 (62.856796 MB) 0.74x (reduction)

DFG: 39117360 (37.305222 MB) 36374400 (34.689331 MB) 0.93x (reduction)

Thunk: 23230968 (22.154778 MB) 22892292 (21.831791 MB) 0.99x

InlineCache: 22027416 (21.006981 MB) 22083508 (21.060474 MB) 1.00x

FTL: 6575772 (6.271145 MB) 6128080 (5.844193 MB) 0.93x (reduction)

Wasm: 2302724 (2.196049 MB) 2309732 (2.202732 MB) 1.00x

YarrJIT: 1538956 (1.467663 MB) 1536104 (1.464943 MB) 1.00x

CSSJIT: 0 0

Uncategorized: 0 0

Benchmarking was done with Speedometer2 and JetSteam2 on an M1 Mac.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::JITData::size const):
(JSC::CodeBlock::dumpValueProfiles):
(JSC::CodeBlock::setRareCaseProfiles): Deleted.
(JSC::CodeBlock::rareCaseProfileForBytecodeIndex): Deleted.
(JSC::CodeBlock::rareCaseProfileCountForBytecodeIndex): Deleted.

• bytecode/CodeBlock.h:

(JSC::CodeBlock::likelyToTakeSlowCase): Deleted.
(JSC::CodeBlock::couldTakeSlowCase): Deleted.

• bytecode/ValueProfile.h:

(JSC::RareCaseProfile::RareCaseProfile): Deleted.
(JSC::getRareCaseProfileBytecodeIndex): Deleted.

• dfg/DFGByteCodeParser.cpp:

(JSC::DFG::ByteCodeParser::makeSafe):
(JSC::DFG::ByteCodeParser::parseBlock):

• jit/JIT.cpp:

(JSC::JIT::privateCompileSlowCases):

File:

• trunk/Source/JavaScriptCore/jit/JIT.cpp (modified) (4 diffs)

trunk/Source/JavaScriptCore/jit/JIT.cpp

@@ -516 +516 @@
     m_callLinkInfoIndex = 0;
 
-    FixedVector<RareCaseProfile> rareCaseProfiles;
-    if (shouldEmitProfiling())
-        rareCaseProfiles = FixedVector<RareCaseProfile>(m_bytecodeCountHavingSlowCase);
-    
     unsigned bytecodeCountHavingSlowCase = 0;
     for (Vector<SlowCaseEntry>::iterator iter = m_slowCases.begin(); iter != m_slowCases.end();) {
@@ -530 +526 @@
         const Instruction* currentInstruction = m_codeBlock->instructions().at(m_bytecodeIndex).ptr();
         
-        RareCaseProfile* rareCaseProfile = nullptr;
-        if (shouldEmitProfiling())
-            rareCaseProfile = &rareCaseProfiles.at(bytecodeCountHavingSlowCase);
-
         if (JITInternal::verbose)
             dataLogLn("Baseline JIT emitting slow code for ", m_bytecodeIndex, " at offset ", (long)debugOffset());
@@ -648 +640 @@
         RELEASE_ASSERT_WITH_MESSAGE(firstTo.offset() == (iter - 1)->to.offset(), "Too many jumps linked in slow case codegen.");
         
-        if (shouldEmitProfiling())
-            add32(TrustedImm32(1), AbsoluteAddress(&rareCaseProfile->m_counter));
-
         emitJumpSlowToHot(jump(), 0);
         ++bytecodeCountHavingSlowCase;
@@ -663 +652 @@
     RELEASE_ASSERT(m_privateBrandAccessIndex == m_privateBrandAccesses.size());
     RELEASE_ASSERT(m_callLinkInfoIndex == m_callCompilationInfo.size());
-
-    if (shouldEmitProfiling())
-        m_codeBlock->setRareCaseProfiles(WTFMove(rareCaseProfiles));
 
 #ifndef NDEBUG