#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<MachineBlockFrequencyInfo>();
+ AU.addRequired<MachineBranchProbabilityInfo>();
AU.addRequired<TargetPassConfig>();
MachineFunctionPass::getAnalysisUsage(AU);
}
// HW that requires structurized CFG.
bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
PassConfig->getEnableTailMerge();
- BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true);
+ BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true,
+ getAnalysis<MachineBlockFrequencyInfo>(),
+ getAnalysis<MachineBranchProbabilityInfo>());
return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(),
MF.getSubtarget().getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
-
-BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist) {
+BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
+ const MachineBlockFrequencyInfo &FreqInfo,
+ const MachineBranchProbabilityInfo &ProbInfo)
+ : EnableHoistCommonCode(CommonHoist), MBBFreqInfo(FreqInfo),
+ MBPI(ProbInfo) {
switch (FlagEnableTailMerge) {
case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
case cl::BOU_TRUE: EnableTailMerge = true; break;
case cl::BOU_FALSE: EnableTailMerge = false; break;
}
-
- EnableHoistCommonCode = CommonHoist;
}
/// RemoveDeadBlock - Remove the specified dead machine basic block from the
// Splice the code over.
NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end());
+ // NewMBB inherits CurMBB's block frequency.
+ MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB));
+
// For targets that use the register scavenger, we must maintain LiveIns.
MaintainLiveIns(&CurMBB, NewMBB);
#endif
}
+BlockFrequency
+BranchFolder::MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const {
+ auto I = MergedBBFreq.find(MBB);
+
+ if (I != MergedBBFreq.end())
+ return I->second;
+
+ return MBFI.getBlockFreq(MBB);
+}
+
+void BranchFolder::MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB,
+ BlockFrequency F) {
+ MergedBBFreq[MBB] = F;
+}
+
/// CountTerminators - Count the number of terminators in the given
/// block and set I to the position of the first non-terminator, if there
/// is one, or MBB->end() otherwise.
}
MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
+
+ // Recompute commont tail MBB's edge weights and block frequency.
+ setCommonTailEdgeWeights(*MBB);
+
// MBB is common tail. Adjust all other BB's to jump to this one.
// Traversal must be forwards so erases work.
DEBUG(dbgs() << "\nUsing common tail in BB#" << MBB->getNumber()
return MadeChange;
}
+void BranchFolder::setCommonTailEdgeWeights(MachineBasicBlock &TailMBB) {
+ SmallVector<BlockFrequency, 2> EdgeFreqLs(TailMBB.succ_size());
+ BlockFrequency AccumulatedMBBFreq;
+
+ // Aggregate edge frequency of successor edge j:
+ // edgeFreq(j) = sum (freq(bb) * edgeProb(bb, j)),
+ // where bb is a basic block that is in SameTails.
+ for (const auto &Src : SameTails) {
+ const MachineBasicBlock *SrcMBB = Src.getBlock();
+ BlockFrequency BlockFreq = MBBFreqInfo.getBlockFreq(SrcMBB);
+ AccumulatedMBBFreq += BlockFreq;
+
+ // It is not necessary to recompute edge weights if TailBB has less than two
+ // successors.
+ if (TailMBB.succ_size() <= 1)
+ continue;
+
+ auto EdgeFreq = EdgeFreqLs.begin();
+
+ for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end();
+ SuccI != SuccE; ++SuccI, ++EdgeFreq)
+ *EdgeFreq += BlockFreq * MBPI.getEdgeProbability(SrcMBB, *SuccI);
+ }
+
+ MBBFreqInfo.setBlockFreq(&TailMBB, AccumulatedMBBFreq);
+
+ if (TailMBB.succ_size() <= 1)
+ return;
+
+ auto MaxEdgeFreq = *std::max_element(EdgeFreqLs.begin(), EdgeFreqLs.end());
+ uint64_t Scale = MaxEdgeFreq.getFrequency() / UINT32_MAX + 1;
+ auto EdgeFreq = EdgeFreqLs.begin();
+
+ for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end();
+ SuccI != SuccE; ++SuccI, ++EdgeFreq)
+ TailMBB.setSuccWeight(SuccI, EdgeFreq->getFrequency() / Scale);
+}
+
//===----------------------------------------------------------------------===//
// Branch Optimization
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/Support/BlockFrequency.h"
#include <vector>
namespace llvm {
+ class MachineBlockFrequencyInfo;
+ class MachineBranchProbabilityInfo;
class MachineFunction;
class MachineModuleInfo;
class RegScavenger;
class BranchFolder {
public:
- explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist);
+ explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
+ const MachineBlockFrequencyInfo &MBFI,
+ const MachineBranchProbabilityInfo &MBPI);
bool OptimizeFunction(MachineFunction &MF,
const TargetInstrInfo *tii,
MachineModuleInfo *MMI;
RegScavenger *RS;
+ /// \brief This class keeps track of branch frequencies of newly created
+ /// blocks and tail-merged blocks.
+ class MBFIWrapper {
+ public:
+ MBFIWrapper(const MachineBlockFrequencyInfo &I) : MBFI(I) {}
+ BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
+ void setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F);
+
+ private:
+ const MachineBlockFrequencyInfo &MBFI;
+ DenseMap<const MachineBasicBlock *, BlockFrequency> MergedBBFreq;
+ };
+
+ MBFIWrapper MBBFreqInfo;
+ const MachineBranchProbabilityInfo &MBPI;
+
bool TailMergeBlocks(MachineFunction &MF);
bool TryTailMergeBlocks(MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB);
+ void setCommonTailEdgeWeights(MachineBasicBlock &TailMBB);
void MaintainLiveIns(MachineBasicBlock *CurMBB,
MachineBasicBlock *NewMBB);
void ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
const TargetLoweringBase *TLI;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
+ const MachineBlockFrequencyInfo *MBFI;
const MachineBranchProbabilityInfo *MBPI;
MachineRegisterInfo *MRI;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<MachineBlockFrequencyInfo>();
AU.addRequired<MachineBranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
TLI = MF.getSubtarget().getTargetLowering();
TII = MF.getSubtarget().getInstrInfo();
TRI = MF.getSubtarget().getRegisterInfo();
+ MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
MRI = &MF.getRegInfo();
bool BFChange = false;
if (!PreRegAlloc) {
// Tail merge tend to expose more if-conversion opportunities.
- BranchFolder BF(true, false);
+ BranchFolder BF(true, false, *MBFI, *MBPI);
BFChange = BF.OptimizeFunction(MF, TII, MF.getSubtarget().getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
BBAnalysis.clear();
if (MadeChange && IfCvtBranchFold) {
- BranchFolder BF(false, false);
+ BranchFolder BF(false, false, *MBFI, *MBPI);
BF.OptimizeFunction(MF, TII, MF.getSubtarget().getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
--- /dev/null
+; RUN: llc -mtriple=arm-apple-ios -print-machineinstrs=branch-folder \
+; RUN: %s -o /dev/null 2>&1 | FileCheck %s
+
+; Branch probability of tailed-merged block:
+;
+; p(L0_L1 -> L2) = p(entry -> L0) * p(L0 -> L2) + p(entry -> L1) * p(L1 -> L2)
+; = 0.2 * 0.6 + 0.8 * 0.3 = 0.36
+; p(L0_L1 -> L3) = p(entry -> L0) * p(L0 -> L3) + p(entry -> L1) * p(L1 -> L3)
+; = 0.2 * 0.4 + 0.8 * 0.7 = 0.64
+
+; CHECK: # Machine code for function test0:
+; CHECK: Successors according to CFG: BB#{{[0-9]+}}(13) BB#{{[0-9]+}}(24)
+; CHECK: BB#{{[0-9]+}}:
+; CHECK: BB#{{[0-9]+}}:
+; CHECK: # End machine code for function test0.
+
+define i32 @test0(i32 %n, i32 %m, i32* nocapture %a, i32* nocapture %b) {
+entry:
+ %cmp = icmp sgt i32 %n, 0
+ br i1 %cmp, label %L0, label %L1, !prof !0
+
+L0: ; preds = %entry
+ store i32 12, i32* %a, align 4
+ store i32 18, i32* %b, align 4
+ %cmp1 = icmp eq i32 %m, 8
+ br i1 %cmp1, label %L2, label %L3, !prof !1
+
+L1: ; preds = %entry
+ store i32 14, i32* %a, align 4
+ store i32 18, i32* %b, align 4
+ %cmp3 = icmp eq i32 %m, 8
+ br i1 %cmp3, label %L2, label %L3, !prof !2
+
+L2: ; preds = %L1, %L0
+ br label %L3
+
+L3: ; preds = %L0, %L1, %L2
+ %retval.0 = phi i32 [ 100, %L2 ], [ 6, %L1 ], [ 6, %L0 ]
+ ret i32 %retval.0
+}
+
+!0 = metadata !{metadata !"branch_weights", i32 200, i32 800}
+!1 = metadata !{metadata !"branch_weights", i32 600, i32 400}
+!2 = metadata !{metadata !"branch_weights", i32 300, i32 700}
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