Changeset 278371 in webkit for trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp

Timestamp:

Jun 2, 2021, 1:45:55 PM (4 years ago)

Author:

[email protected]

Message:

We should drop B3 values while running Air
​https://bugs.webkit.org/show_bug.cgi?id=226187

Reviewed by Saam Barati.

We must keep the following values:

• WasmBoundsCheck, to know whether it is Pinned or Maximum, and if it is pinned find its argument.
• CCall/Patch/Check/CheckAdd/CheckSub/CheckMul and all of their children, because all of these are lowered to Air::Patchpoint, which needs to know the type of its arguments, and does so by looking at the children of its origin.

I intend to fix these in later patches if possible.

Finally we must preserve all B3 values in the following cases:

• if we dump the disassembly or the Air graph: because otherwise we cannot print the origins
• if we are using the sampling profiler, because it relies on PCToCodeOriginMap which we cannot accurately fill without these origins.

We must also keep m_tuples alive, as it is used by Patchpoints in Air to understand the types of their arguments.
We also don't touch StackSlots (in this patch), because one of them is captured by FTL::State.

Also now PCToOriginMap has a Vector with no inline capacity, since it is either quite large (if needed) or empty (otherwise).

The performance impact of this is a progression on various RAMification subtests on Mac, but is more mitigated on iPhone7, with various regressions.
I suspect these to be noise, and will monitor the performance bots post-landing to make sure of it.

• b3/B3LowerToAir.cpp:

(JSC::B3::lowerToAir):

• b3/B3Procedure.cpp:

(JSC::B3::Procedure::freeUnneededB3ValuesAfterLowering):

• b3/B3Procedure.h:

(JSC::B3::Procedure::releasePCToOriginMap):
(JSC::B3::Procedure::setNeedsPCToOriginMap):
(JSC::B3::Procedure::needsPCToOriginMap):

• b3/B3SparseCollection.h:

(JSC::B3::SparseCollection::clearAll):
(JSC::B3::SparseCollection::filterAndTransfer):

• b3/air/AirCode.cpp:

(JSC::B3::Air::Code::Code):

• b3/air/AirCode.h:

(JSC::B3::Air::Code::shouldPreserveB3Origins const):

• b3/air/AirGenerate.cpp:

(JSC::B3::Air::generateWithAlreadyAllocatedRegisters):

• ftl/FTLCompile.cpp:

(JSC::FTL::compile):

• ftl/FTLState.cpp:

(JSC::FTL::State::State):

File:

• trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ftl/FTLCompile.cpp

@@ -151 +151 @@
         return;
     }
-    
-    B3::PCToOriginMap originMap = state.proc->releasePCToOriginMap();
-    if (vm.shouldBuilderPCToCodeOriginMapping())
+
+    if (vm.shouldBuilderPCToCodeOriginMapping()) {
+        B3::PCToOriginMap originMap = state.proc->releasePCToOriginMap();
         codeBlock->setPCToCodeOriginMap(makeUnique<PCToCodeOriginMap>(PCToCodeOriginMapBuilder(vm, WTFMove(originMap)), *state.finalizer->b3CodeLinkBuffer));
+    }
 
     CodeLocationLabel<JSEntryPtrTag> label = state.finalizer->b3CodeLinkBuffer->locationOf<JSEntryPtrTag>(state.proc->code().entrypointLabel(0));