[llvm] r219123 - DbgValueHistoryCalculator: Store modified registers in a BitVector instead of std::set.
Benjamin Kramer
benny.kra at gmail.com
Mon Oct 6 10:09:52 PDT 2014
On 06.10.2014, at 18:29, Frédéric Riss <friss at apple.com> wrote:
>
>> On Oct 6, 2014, at 8:31 AM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
>>
>> Author: d0k
>> Date: Mon Oct 6 10:31:04 2014
>> New Revision: 219123
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=219123&view=rev
>> Log:
>> DbgValueHistoryCalculator: Store modified registers in a BitVector instead of std::set.
>>
>> And iterate over the smaller map instead of the larger set first. Reduces the time spent in
>> calculateDbgValueHistory by 30-40%.
>
> Cool! Do you have a specific testcase where this shows up? how did you measure it? When I last worked on that code, I tried the BitVector approach and it didn’t give me any gain on my specific testcase. I’ll try to run my testcase again.
This was on a large-ish .c test case with clang -O2 -g under a profiler. This function wasn't particularly hot but std::set always catches my eye ;)
- Ben
>
>> Modified:
>> llvm/trunk/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp?rev=219123&r1=219122&r2=219123&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp Mon Oct 6 10:31:04 2014
>> @@ -8,6 +8,7 @@
>> //===----------------------------------------------------------------------===//
>>
>> #include "DbgValueHistoryCalculator.h"
>> +#include "llvm/ADT/BitVector.h"
>> #include "llvm/ADT/SmallVector.h"
>> #include "llvm/CodeGen/MachineBasicBlock.h"
>> #include "llvm/CodeGen/MachineFunction.h"
>> @@ -16,12 +17,10 @@
>> #include "llvm/Target/TargetRegisterInfo.h"
>> #include <algorithm>
>> #include <map>
>> -#include <set>
>> +using namespace llvm;
>>
>> #define DEBUG_TYPE "dwarfdebug"
>>
>> -namespace llvm {
>> -
>> // \brief If @MI is a DBG_VALUE with debug value described by a
>> // defined register, returns the number of this register.
>> // In the other case, returns 0.
>> @@ -97,6 +96,19 @@ static void addRegDescribedVar(RegDescri
>> VarSet.push_back(Var);
>> }
>>
>> +// \brief Terminate the location range for variables described by register at
>> +// @I by inserting @ClobberingInstr to their history.
>> +static void clobberRegisterUses(RegDescribedVarsMap &RegVars,
>> + RegDescribedVarsMap::iterator I,
>> + DbgValueHistoryMap &HistMap,
>> + const MachineInstr &ClobberingInstr) {
>> + // Iterate over all variables described by this register and add this
>> + // instruction to their history, clobbering it.
>> + for (const auto &Var : I->second)
>> + HistMap.endInstrRange(Var, ClobberingInstr);
>> + RegVars.erase(I);
>> +}
>> +
>> // \brief Terminate the location range for variables described by register
>> // @RegNo by inserting @ClobberingInstr to their history.
>> static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
>> @@ -105,11 +117,7 @@ static void clobberRegisterUses(RegDescr
>> const auto &I = RegVars.find(RegNo);
>> if (I == RegVars.end())
>> return;
>> - // Iterate over all variables described by this register and add this
>> - // instruction to their history, clobbering it.
>> - for (const auto &Var : I->second)
>> - HistMap.endInstrRange(Var, ClobberingInstr);
>> - RegVars.erase(I);
>> + clobberRegisterUses(RegVars, I, HistMap, ClobberingInstr);
>> }
>>
>> // \brief Collect all registers clobbered by @MI and apply the functor
>> @@ -142,11 +150,12 @@ static const MachineInstr *getFirstEpilo
>> // as the return instruction.
>> DebugLoc LastLoc = LastMI->getDebugLoc();
>> auto Res = LastMI;
>> - for (MachineBasicBlock::const_reverse_iterator I(std::next(LastMI)); I != MBB.rend();
>> - ++I) {
>> + for (MachineBasicBlock::const_reverse_iterator I(std::next(LastMI)),
>> + E = MBB.rend();
>> + I != E; ++I) {
>> if (I->getDebugLoc() != LastLoc)
>> return Res;
>> - Res = std::prev(I.base());
>> + Res = &*I;
>> }
>> // If all instructions have the same debug location, assume whole MBB is
>> // an epilogue.
>> @@ -157,7 +166,7 @@ static const MachineInstr *getFirstEpilo
>> // contents is changed outside of the prologue and epilogue).
>> static void collectChangingRegs(const MachineFunction *MF,
>> const TargetRegisterInfo *TRI,
>> - std::set<unsigned> &Regs) {
>> + BitVector &Regs) {
>> for (const auto &MBB : *MF) {
>> auto FirstEpilogueInst = getFirstEpilogueInst(MBB);
>>
>> @@ -165,15 +174,15 @@ static void collectChangingRegs(const Ma
>> if (&MI == FirstEpilogueInst)
>> break;
>> if (!MI.getFlag(MachineInstr::FrameSetup))
>> - applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.insert(r); });
>> + applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.set(r); });
>> }
>> }
>> }
>>
>> -void calculateDbgValueHistory(const MachineFunction *MF,
>> - const TargetRegisterInfo *TRI,
>> - DbgValueHistoryMap &Result) {
>> - std::set<unsigned> ChangingRegs;
>> +void llvm::calculateDbgValueHistory(const MachineFunction *MF,
>> + const TargetRegisterInfo *TRI,
>> + DbgValueHistoryMap &Result) {
>> + BitVector ChangingRegs(TRI->getNumRegs());
>> collectChangingRegs(MF, TRI, ChangingRegs);
>>
>> RegDescribedVarsMap RegVars;
>> @@ -183,7 +192,7 @@ void calculateDbgValueHistory(const Mach
>> // Not a DBG_VALUE instruction. It may clobber registers which describe
>> // some variables.
>> applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) {
>> - if (ChangingRegs.count(RegNo))
>> + if (ChangingRegs.test(RegNo))
>> clobberRegisterUses(RegVars, RegNo, Result, MI);
>> });
>> continue;
>> @@ -207,11 +216,12 @@ void calculateDbgValueHistory(const Mach
>> // Make sure locations for register-described variables are valid only
>> // until the end of the basic block (unless it's the last basic block, in
>> // which case let their liveness run off to the end of the function).
>> - if (!MBB.empty() && &MBB != &MF->back()) {
>> - for (unsigned RegNo : ChangingRegs)
>> - clobberRegisterUses(RegVars, RegNo, Result, MBB.back());
>> + if (!MBB.empty() && &MBB != &MF->back()) {
>> + for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
>> + auto CurElem = I++; // CurElem can be erased below.
>> + if (ChangingRegs.test(CurElem->first))
>> + clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
>> + }
>> }
>> }
>> }
>> -
>> -}
>>
>>
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