[llvm] r219123 - DbgValueHistoryCalculator: Store modified registers in a BitVector instead of std::set.
Alexey Samsonov
vonosmas at gmail.com
Mon Oct 6 10:22:50 PDT 2014
On Mon, Oct 6, 2014 at 10:09 AM, Benjamin Kramer <benny.kra at gmail.com>
wrote:
>
> 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 ;)
>
Thanks for the change!
>
> - 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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> >> llvm-commits at cs.uiuc.edu
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> >
>
>
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--
Alexey Samsonov
vonosmas at gmail.com
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