Changeset 261930 in webkit

Timestamp:

May 20, 2020 10:48:22 AM (4 years ago)

Author:

msaboff@apple.com

Message:

[Wasm] Limit the size of Wasm function we optimize in OMG mode
​https://bugs.webkit.org/show_bug.cgi?id=212105

Reviewed by Filip Pizlo.

Given that memory grows O(N^{2) compiling Wasm code through the OMG path,
we can run out of memory when compiling large Wasm functions. This change adds
a limit option, webAssemblyBBQFallbackSize, When the Wasm function size is
equal to or greater than this limit we always compile using BBQ optimization
parameters.}

As part of this change, we still go through the OMG loop entry OSR code
generation path for functions that are at or above the threshold, but we
compile such functions with BBQ compilation optimization levels.
Also for Wasm functions at or above the threashold, we don't tier up to an
OMG compiled normal entry function. Instead we stay with the BBQ compiled version.

• runtime/OptionsList.h:
• wasm/WasmAirIRGenerator.cpp:

(JSC::Wasm::AirIRGenerator::AirIRGenerator):

• wasm/WasmB3IRGenerator.cpp:

(JSC::Wasm::B3IRGenerator::B3IRGenerator):
(JSC::Wasm::parseAndCompile):

• wasm/WasmCompilationMode.cpp:

(JSC::Wasm::wasmFunctionSizeCanBeOMGCompiled):

• wasm/WasmCompilationMode.h:
• wasm/WasmOperations.cpp:

(JSC::Wasm::operationWasmTriggerOSREntryNow):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/OptionsList.h (modified) (1 diff)
• wasm/WasmAirIRGenerator.cpp (modified) (1 diff)
• wasm/WasmB3IRGenerator.cpp (modified) (2 diffs)
• wasm/WasmCompilationMode.cpp (modified) (2 diffs)
• wasm/WasmCompilationMode.h (modified) (1 diff)
• wasm/WasmOperations.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2020-05-20  Michael Saboff  <msaboff@apple.com>
+
+        [Wasm] Limit the size of Wasm function we optimize in OMG mode
+        https://bugs.webkit.org/show_bug.cgi?id=212105
+
+        Reviewed by Filip Pizlo.
+
+        Given that memory grows O(N^2) compiling Wasm code through the OMG path,
+        we can run out of memory when compiling large Wasm functions.  This change adds
+        a limit option, webAssemblyBBQFallbackSize,  When the Wasm function size is
+        equal to or greater than this limit we always compile using BBQ optimization
+        parameters.
+
+        As part of this change, we still go through the OMG loop entry OSR code
+        generation path for functions that are at or above the threshold, but we
+        compile such functions with BBQ compilation optimization levels.
+        Also for Wasm functions at or above  the threashold, we don't tier up to an
+        OMG compiled normal entry function.  Instead we stay with the BBQ compiled version.
+
+        * runtime/OptionsList.h:
+        * wasm/WasmAirIRGenerator.cpp:
+        (JSC::Wasm::AirIRGenerator::AirIRGenerator):
+        * wasm/WasmB3IRGenerator.cpp:
+        (JSC::Wasm::B3IRGenerator::B3IRGenerator):
+        (JSC::Wasm::parseAndCompile):
+        * wasm/WasmCompilationMode.cpp:
+        (JSC::Wasm::wasmFunctionSizeCanBeOMGCompiled):
+        * wasm/WasmCompilationMode.h:
+        * wasm/WasmOperations.cpp:
+        (JSC::Wasm::operationWasmTriggerOSREntryNow):
+
 2020-05-19  Ross Kirsling  <ross.kirsling@sony.com>
 

trunk/Source/JavaScriptCore/runtime/OptionsList.h

@@ -454 +454 @@
     v(Unsigned, webAssemblyBBQB3OptimizationLevel, 1, Normal, "B3 Optimization level for BBQ Web Assembly module compilations.") \
     v(Unsigned, webAssemblyOMGOptimizationLevel, Options::defaultB3OptLevel(), Normal, "B3 Optimization level for OMG Web Assembly module compilations.") \
+    v(Unsigned, webAssemblyBBQFallbackSize, 50000, Normal, "Limit of Wasm function size above which we fallback to BBQ compilation mode.") \
     \
     v(Bool, useBBQTierUpChecks, true, Normal, "Enables tier up checks for our BBQ code.") \

trunk/Source/JavaScriptCore/wasm/WasmAirIRGenerator.cpp

@@ -894 +894 @@
     }
 
-    emitEntryTierUpCheck();
+    if (wasmFunctionSizeCanBeOMGCompiled(m_info.functions[m_functionIndex].data.size()))
+        emitEntryTierUpCheck();
 }
 

trunk/Source/JavaScriptCore/wasm/WasmB3IRGenerator.cpp

@@ -538 +538 @@
     }
 
-    emitEntryTierUpCheck();
+    if (wasmFunctionSizeCanBeOMGCompiled(m_info.functions[m_functionIndex].data.size()))
+        emitEntryTierUpCheck();
 
     if (m_compilationMode == CompilationMode::OMGForOSREntryMode)
@@ -1974 +1975 @@
     procedure.setNeedsUsedRegisters(false);
     
-    procedure.setOptLevel(compilationMode == CompilationMode::BBQMode
+    procedure.setOptLevel(compilationMode == CompilationMode::BBQMode || !wasmFunctionSizeCanBeOMGCompiled(function.data.size())
         ? Options::webAssemblyBBQB3OptimizationLevel()
         : Options::webAssemblyOMGOptimizationLevel());

trunk/Source/JavaScriptCore/wasm/WasmCompilationMode.cpp

@@ -27 +27 @@
 #include "WasmCompilationMode.h"
 
+#include "Options.h"
 #include <wtf/Assertions.h>
 
@@ -49 +50 @@
 }
 
+bool wasmFunctionSizeCanBeOMGCompiled(size_t size)
+{
+    return size < Options::webAssemblyBBQFallbackSize();
+}
+
 } } // namespace JSC::Wasm

trunk/Source/JavaScriptCore/wasm/WasmCompilationMode.h

@@ -37 +37 @@
 
 const char* makeString(CompilationMode);
+bool wasmFunctionSizeCanBeOMGCompiled(size_t);
 
 } } // namespace JSC::Wasm

trunk/Source/JavaScriptCore/wasm/WasmOperations.cpp

@@ -271 +271 @@
 
     if (!Options::useWebAssemblyOSR()) {
+        if (!wasmFunctionSizeCanBeOMGCompiled(instance->module().moduleInformation().functions[functionIndex].data.size())) {
+            tierUp.deferIndefinitely();
+            return returnWithoutOSREntry();
+        }
+
         if (shouldTriggerOMGCompile(tierUp, callee.replacement(), functionIndex))
             triggerOMGReplacementCompile(tierUp, callee.replacement(), instance, codeBlock, functionIndex);
@@ -337 +342 @@
 
     if (!triggeredSlowPathToStartCompilation) {
+        if (!wasmFunctionSizeCanBeOMGCompiled(instance->module().moduleInformation().functions[functionIndex].data.size()))
+            return returnWithoutOSREntry();
+
         triggerOMGReplacementCompile(tierUp, callee.replacement(), instance, codeBlock, functionIndex);