WIP: [VE] fix AND reductions on mask types #83
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kaz7
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Sep 25, 2023
…… (#67069) We noticed some performance issue while in lldb-vscode for grabing the name of the SBValue. Profiling shows SBValue::GetName() can cause synthetic children provider of shared/unique_ptr to deference underlying object and complete it type. This patch lazily moves the dereference from synthetic child provider's Update() method to GetChildAtIndex() so that SBValue::GetName() won't trigger the slow code path. Here is the culprit slow code path: ``` ... frame #59: 0x00007ff4102e0660 liblldb.so.15`SymbolFileDWARF::CompleteType(this=<unavailable>, compiler_type=0x00007ffdd9829450) at SymbolFileDWARF.cpp:1567:25 [opt] ... frame #67: 0x00007ff40fdf9bd4 liblldb.so.15`lldb_private::ValueObject::Dereference(this=0x0000022bb5dfe980, error=0x00007ffdd9829970) at ValueObject.cpp:2672:41 [opt] frame #68: 0x00007ff41011bb0a liblldb.so.15`(anonymous namespace)::LibStdcppSharedPtrSyntheticFrontEnd::Update(this=0x000002298fb94380) at LibStdcpp.cpp:403:40 [opt] frame #69: 0x00007ff41011af9a liblldb.so.15`lldb_private::formatters::LibStdcppSharedPtrSyntheticFrontEndCreator(lldb_private::CXXSyntheticChildren*, std::shared_ptr<lldb_private::ValueObject>) [inlined] (anonymous namespace)::LibStdcppSharedPtrSyntheticFrontEnd::LibStdcppSharedPtrSyntheticFrontEnd(this=0x000002298fb94380, valobj_sp=<unavailable>) at LibStdcpp.cpp:371:5 [opt] ... frame #78: 0x00007ff40fdf6e42 liblldb.so.15`lldb_private::ValueObject::CalculateSyntheticValue(this=0x000002296c66a500) at ValueObject.cpp:1836:27 [opt] frame #79: 0x00007ff40fdf1939 liblldb.so.15`lldb_private::ValueObject::GetSyntheticValue(this=<unavailable>) at ValueObject.cpp:1867:3 [opt] frame #80: 0x00007ff40fc89008 liblldb.so.15`ValueImpl::GetSP(this=0x0000022c71b90de0, stop_locker=0x00007ffdd9829d00, lock=0x00007ffdd9829d08, error=0x00007ffdd9829d18) at SBValue.cpp:141:46 [opt] frame #81: 0x00007ff40fc7d82a liblldb.so.15`lldb::SBValue::GetSP(ValueLocker&) const [inlined] ValueLocker::GetLockedSP(this=0x00007ffdd9829d00, in_value=<unavailable>) at SBValue.cpp:208:21 [opt] frame #82: 0x00007ff40fc7d817 liblldb.so.15`lldb::SBValue::GetSP(this=0x00007ffdd9829d90, locker=0x00007ffdd9829d00) const at SBValue.cpp:1047:17 [opt] frame #83: 0x00007ff40fc7da6f liblldb.so.15`lldb::SBValue::GetName(this=0x00007ffdd9829d90) at SBValue.cpp:294:32 [opt] ... ``` Differential Revision: https://reviews.llvm.org/D159542
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This is a work-in-progress because of unwanted spilling.
The patch fixes AND reduction codegen for mask types (v256i1, v512i1).
Still with fastisel disabled and the fixed codegen, we are again getting spills (cf #82 ). Eg
vm0is copied to another mask register only to be used directly - we run out of mask registers to allocate.