Revert "[MBP] Reduce code size by running tail merging in MBP."
This reverts commit r271930, r271915, r271923. They break a thumb selfhosting
bot.
llvm-svn: 272017
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 63ffc1f..c4c060f 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -27,7 +27,6 @@
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineMemOperand.h"
-#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
@@ -100,9 +99,8 @@
// HW that requires structurized CFG.
bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
PassConfig->getEnableTailMerge();
- BranchFolder::MBFIWrapper MBBFreqInfo(
- getAnalysis<MachineBlockFrequencyInfo>());
- BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true, MBBFreqInfo,
+ BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true,
+ getAnalysis<MachineBlockFrequencyInfo>(),
getAnalysis<MachineBranchProbabilityInfo>());
return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(),
MF.getSubtarget().getRegisterInfo(),
@@ -110,7 +108,7 @@
}
BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
- MBFIWrapper &FreqInfo,
+ const MachineBlockFrequencyInfo &FreqInfo,
const MachineBranchProbabilityInfo &ProbInfo)
: EnableHoistCommonCode(CommonHoist), MBBFreqInfo(FreqInfo),
MBPI(ProbInfo) {
@@ -138,8 +136,6 @@
// Remove the block.
MF->erase(MBB);
FuncletMembership.erase(MBB);
- if (MLI)
- MLI->removeBlock(MBB);
}
/// OptimizeImpDefsBlock - If a basic block is just a bunch of implicit_def
@@ -196,22 +192,18 @@
}
/// OptimizeFunction - Perhaps branch folding, tail merging and other
-/// CFG optimizations on the given function. Block placement changes the layout
-/// and may create new tail merging opportunities.
+/// CFG optimizations on the given function.
bool BranchFolder::OptimizeFunction(MachineFunction &MF,
const TargetInstrInfo *tii,
const TargetRegisterInfo *tri,
- MachineModuleInfo *mmi,
- MachineLoopInfo *mli, bool AfterPlacement) {
+ MachineModuleInfo *mmi) {
if (!tii) return false;
TriedMerging.clear();
- AfterBlockPlacement = AfterPlacement;
TII = tii;
TRI = tri;
MMI = mmi;
- MLI = mli;
RS = nullptr;
// Use a RegScavenger to help update liveness when required.
@@ -237,10 +229,7 @@
bool MadeChangeThisIteration = true;
while (MadeChangeThisIteration) {
MadeChangeThisIteration = TailMergeBlocks(MF);
- // No need to clean up if tail merging does not change anything after the
- // block placement.
- if (!AfterBlockPlacement || MadeChangeThisIteration)
- MadeChangeThisIteration |= OptimizeBranches(MF);
+ MadeChangeThisIteration |= OptimizeBranches(MF);
if (EnableHoistCommonCode)
MadeChangeThisIteration |= HoistCommonCode(MF);
MadeChange |= MadeChangeThisIteration;
@@ -457,11 +446,6 @@
// Splice the code over.
NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end());
- // NewMBB belongs to the same loop as CurMBB.
- if (MLI)
- if (MachineLoop *ML = MLI->getLoopFor(&CurMBB))
- ML->addBasicBlockToLoop(NewMBB, MLI->getBase());
-
// NewMBB inherits CurMBB's block frequency.
MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB));
@@ -556,18 +540,6 @@
MergedBBFreq[MBB] = F;
}
-raw_ostream &
-BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS,
- const MachineBasicBlock *MBB) const {
- return MBFI.printBlockFreq(OS, getBlockFreq(MBB));
-}
-
-raw_ostream &
-BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS,
- const BlockFrequency Freq) const {
- return MBFI.printBlockFreq(OS, Freq);
-}
-
/// 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.
@@ -949,28 +921,24 @@
if (!EnableTailMerge) return MadeChange;
// First find blocks with no successors.
- // Block placement does not create new tail merging opportunities for these
- // blocks.
- if (!AfterBlockPlacement) {
- MergePotentials.clear();
- for (MachineBasicBlock &MBB : MF) {
- if (MergePotentials.size() == TailMergeThreshold)
- break;
- if (!TriedMerging.count(&MBB) && MBB.succ_empty())
- MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(MBB), &MBB));
- }
-
- // If this is a large problem, avoid visiting the same basic blocks
- // multiple times.
+ MergePotentials.clear();
+ for (MachineBasicBlock &MBB : MF) {
if (MergePotentials.size() == TailMergeThreshold)
- for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
- TriedMerging.insert(MergePotentials[i].getBlock());
-
- // See if we can do any tail merging on those.
- if (MergePotentials.size() >= 2)
- MadeChange |= TryTailMergeBlocks(nullptr, nullptr);
+ break;
+ if (!TriedMerging.count(&MBB) && MBB.succ_empty())
+ MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(MBB), &MBB));
}
+ // If this is a large problem, avoid visiting the same basic blocks
+ // multiple times.
+ if (MergePotentials.size() == TailMergeThreshold)
+ for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
+ TriedMerging.insert(MergePotentials[i].getBlock());
+
+ // See if we can do any tail merging on those.
+ if (MergePotentials.size() >= 2)
+ MadeChange |= TryTailMergeBlocks(nullptr, nullptr);
+
// Look at blocks (IBB) with multiple predecessors (PBB).
// We change each predecessor to a canonical form, by
// (1) temporarily removing any unconditional branch from the predecessor
@@ -1016,17 +984,6 @@
if (PBB->hasEHPadSuccessor())
continue;
- // Bail out if the loop header (IBB) is not the top of the loop chain
- // after the block placement. Otherwise, the common tail of IBB's
- // predecessors may become the loop top if block placement is called again
- // and the predecessors may branch to this common tail.
- // FIXME: Relaxed this check if the algorithm of finding loop top is
- // changed in MBP.
- if (AfterBlockPlacement && MLI)
- if (MachineLoop *ML = MLI->getLoopFor(IBB))
- if (IBB == ML->getHeader() && ML == MLI->getLoopFor(PBB))
- continue;
-
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
diff --git a/llvm/lib/CodeGen/BranchFolding.h b/llvm/lib/CodeGen/BranchFolding.h
index f704099..d759d53 100644
--- a/llvm/lib/CodeGen/BranchFolding.h
+++ b/llvm/lib/CodeGen/BranchFolding.h
@@ -20,24 +20,20 @@
class MachineBranchProbabilityInfo;
class MachineFunction;
class MachineModuleInfo;
- class MachineLoopInfo;
class RegScavenger;
class TargetInstrInfo;
class TargetRegisterInfo;
class LLVM_LIBRARY_VISIBILITY BranchFolder {
public:
- class MBFIWrapper;
-
explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
- MBFIWrapper &MBFI,
+ const MachineBlockFrequencyInfo &MBFI,
const MachineBranchProbabilityInfo &MBPI);
- bool OptimizeFunction(MachineFunction &MF, const TargetInstrInfo *tii,
- const TargetRegisterInfo *tri, MachineModuleInfo *mmi,
- MachineLoopInfo *mli = nullptr,
- bool AfterPlacement = false);
-
+ bool OptimizeFunction(MachineFunction &MF,
+ const TargetInstrInfo *tii,
+ const TargetRegisterInfo *tri,
+ MachineModuleInfo *mmi);
private:
class MergePotentialsElt {
unsigned Hash;
@@ -95,16 +91,13 @@
};
std::vector<SameTailElt> SameTails;
- bool AfterBlockPlacement;
bool EnableTailMerge;
bool EnableHoistCommonCode;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
MachineModuleInfo *MMI;
- MachineLoopInfo *MLI;
RegScavenger *RS;
- public:
/// \brief This class keeps track of branch frequencies of newly created
/// blocks and tail-merged blocks.
class MBFIWrapper {
@@ -112,18 +105,13 @@
MBFIWrapper(const MachineBlockFrequencyInfo &I) : MBFI(I) {}
BlockFrequency getBlockFreq(const MachineBasicBlock *MBB) const;
void setBlockFreq(const MachineBasicBlock *MBB, BlockFrequency F);
- raw_ostream &printBlockFreq(raw_ostream &OS,
- const MachineBasicBlock *MBB) const;
- raw_ostream &printBlockFreq(raw_ostream &OS,
- const BlockFrequency Freq) const;
private:
const MachineBlockFrequencyInfo &MBFI;
DenseMap<const MachineBasicBlock *, BlockFrequency> MergedBBFreq;
};
- private:
- MBFIWrapper &MBBFreqInfo;
+ MBFIWrapper MBBFreqInfo;
const MachineBranchProbabilityInfo &MBPI;
bool TailMergeBlocks(MachineFunction &MF);
diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp
index 5fd18ed..c2586b5 100644
--- a/llvm/lib/CodeGen/IfConversion.cpp
+++ b/llvm/lib/CodeGen/IfConversion.cpp
@@ -163,6 +163,7 @@
const TargetLoweringBase *TLI;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
+ const MachineBlockFrequencyInfo *MBFI;
const MachineBranchProbabilityInfo *MBPI;
MachineRegisterInfo *MRI;
@@ -290,7 +291,7 @@
TLI = ST.getTargetLowering();
TII = ST.getInstrInfo();
TRI = ST.getRegisterInfo();
- BranchFolder::MBFIWrapper MBFI(getAnalysis<MachineBlockFrequencyInfo>());
+ MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
MRI = &MF.getRegInfo();
SchedModel.init(ST.getSchedModel(), &ST, TII);
@@ -302,7 +303,7 @@
bool BFChange = false;
if (!PreRegAlloc) {
// Tail merge tend to expose more if-conversion opportunities.
- BranchFolder BF(true, false, MBFI, *MBPI);
+ BranchFolder BF(true, false, *MBFI, *MBPI);
BFChange = BF.OptimizeFunction(MF, TII, ST.getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
@@ -426,7 +427,7 @@
BBAnalysis.clear();
if (MadeChange && IfCvtBranchFold) {
- BranchFolder BF(false, false, MBFI, *MBPI);
+ BranchFolder BF(false, false, *MBFI, *MBPI);
BF.OptimizeFunction(MF, TII, MF.getSubtarget().getRegisterInfo(),
getAnalysisIfAvailable<MachineModuleInfo>());
}
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 42bad4c..c562af9 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -26,8 +26,6 @@
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/TargetPassConfig.h"
-#include "BranchFolding.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
@@ -118,12 +116,6 @@
cl::desc("Cost of jump instructions."),
cl::init(1), cl::Hidden);
-static cl::opt<bool>
-BranchFoldPlacement("branch-fold-placement",
- cl::desc("Perform branch folding during placement. "
- "Reduces code size."),
- cl::init(true), cl::Hidden);
-
extern cl::opt<unsigned> StaticLikelyProb;
namespace {
@@ -240,10 +232,10 @@
const MachineBranchProbabilityInfo *MBPI;
/// \brief A handle to the function-wide block frequency pass.
- std::unique_ptr<BranchFolder::MBFIWrapper> MBFI;
+ const MachineBlockFrequencyInfo *MBFI;
/// \brief A handle to the loop info.
- MachineLoopInfo *MLI;
+ const MachineLoopInfo *MLI;
/// \brief A handle to the target's instruction info.
const TargetInstrInfo *TII;
@@ -331,7 +323,6 @@
AU.addRequired<MachineBlockFrequencyInfo>();
AU.addRequired<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
- AU.addRequired<TargetPassConfig>();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
@@ -1471,8 +1462,7 @@
return false;
MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
- MBFI = llvm::make_unique<BranchFolder::MBFIWrapper>(
- getAnalysis<MachineBlockFrequencyInfo>());
+ MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
MLI = &getAnalysis<MachineLoopInfo>();
TII = F.getSubtarget().getInstrInfo();
TLI = F.getSubtarget().getTargetLowering();
@@ -1480,29 +1470,6 @@
assert(BlockToChain.empty());
buildCFGChains(F);
-
- // Changing the layout can create new tail merging opportunities.
- TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
- // TailMerge can create jump into if branches that make CFG irreducible for
- // HW that requires structurized CFG.
- bool EnableTailMerge = !F.getTarget().requiresStructuredCFG() &&
- PassConfig->getEnableTailMerge() &&
- BranchFoldPlacement;
- // No tail merging opportunities if the block number is less than four.
- if (F.size() > 3 && EnableTailMerge) {
- BranchFolder BF(/*EnableTailMerge=*/true, /*CommonHoist=*/false, *MBFI,
- *MBPI);
-
- if (BF.OptimizeFunction(F, TII, F.getSubtarget().getRegisterInfo(),
- getAnalysisIfAvailable<MachineModuleInfo>(), MLI,
- /*AfterBlockPlacement=*/true)) {
- // Redo the layout if tail merging creates/removes/moves blocks.
- BlockToChain.clear();
- ChainAllocator.DestroyAll();
- buildCFGChains(F);
- }
- }
-
optimizeBranches(F);
alignBlocks(F);