// if it loads to virtual registers and the virtual register defined has
// a single use.
//
-// - Optimize Copies and Bitcast:
+// - Optimize Copies and Bitcast (more generally, target specific copies):
//
// Rewrite copies and bitcasts to avoid cross register bank copies
// when possible.
// C = copy A <-- same-bank copy
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "peephole-opt"
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include <utility>
using namespace llvm;
+#define DEBUG_TYPE "peephole-opt"
+
// Optimize Extensions
static cl::opt<bool>
Aggressive("aggressive-ext-opt", cl::Hidden,
DisablePeephole("disable-peephole", cl::Hidden, cl::init(false),
cl::desc("Disable the peephole optimizer"));
+static cl::opt<bool>
+DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(false),
+ cl::desc("Disable advanced copy optimization"));
+
STATISTIC(NumReuse, "Number of extension results reused");
STATISTIC(NumCmps, "Number of compares eliminated");
STATISTIC(NumImmFold, "Number of move immediate folded");
STATISTIC(NumLoadFold, "Number of loads folded");
STATISTIC(NumSelects, "Number of selects optimized");
-STATISTIC(NumCopiesBitcasts, "Number of copies/bitcasts optimized");
+STATISTIC(NumUncoalescableCopies, "Number of uncoalescable copies optimized");
+STATISTIC(NumRewrittenCopies, "Number of copies rewritten");
namespace {
class PeepholeOptimizer : public MachineFunctionPass {
- const TargetMachine *TM;
+ MachineFunction *MF;
const TargetInstrInfo *TII;
+ const TargetRegisterInfo *TRI;
MachineRegisterInfo *MRI;
MachineDominatorTree *DT; // Machine dominator tree
private:
bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
- SmallPtrSet<MachineInstr*, 8> &LocalMIs);
+ SmallPtrSetImpl<MachineInstr*> &LocalMIs);
bool optimizeSelect(MachineInstr *MI);
bool optimizeCopyOrBitcast(MachineInstr *MI);
+ bool optimizeCoalescableCopy(MachineInstr *MI);
+ bool optimizeUncoalescableCopy(MachineInstr *MI,
+ SmallPtrSetImpl<MachineInstr *> &LocalMIs);
+ bool findNextSource(unsigned &Reg, unsigned &SubReg);
bool isMoveImmediate(MachineInstr *MI,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
bool isLoadFoldable(MachineInstr *MI,
SmallSet<unsigned, 16> &FoldAsLoadDefCandidates);
+
+ /// \brief Check whether \p MI is understood by the register coalescer
+ /// but may require some rewriting.
+ bool isCoalescableCopy(const MachineInstr &MI) {
+ // SubregToRegs are not interesting, because they are already register
+ // coalescer friendly.
+ return MI.isCopy() || (!DisableAdvCopyOpt &&
+ (MI.isRegSequence() || MI.isInsertSubreg() ||
+ MI.isExtractSubreg()));
+ }
+
+ /// \brief Check whether \p MI is a copy like instruction that is
+ /// not recognized by the register coalescer.
+ bool isUncoalescableCopy(const MachineInstr &MI) {
+ return MI.isBitcast() ||
+ (!DisableAdvCopyOpt &&
+ (MI.isRegSequenceLike() || MI.isInsertSubregLike() ||
+ MI.isExtractSubregLike()));
+ }
+ };
+
+ /// \brief Helper class to track the possible sources of a value defined by
+ /// a (chain of) copy related instructions.
+ /// Given a definition (instruction and definition index), this class
+ /// follows the use-def chain to find successive suitable sources.
+ /// The given source can be used to rewrite the definition into
+ /// def = COPY src.
+ ///
+ /// For instance, let us consider the following snippet:
+ /// v0 =
+ /// v2 = INSERT_SUBREG v1, v0, sub0
+ /// def = COPY v2.sub0
+ ///
+ /// Using a ValueTracker for def = COPY v2.sub0 will give the following
+ /// suitable sources:
+ /// v2.sub0 and v0.
+ /// Then, def can be rewritten into def = COPY v0.
+ class ValueTracker {
+ private:
+ /// The current point into the use-def chain.
+ const MachineInstr *Def;
+ /// The index of the definition in Def.
+ unsigned DefIdx;
+ /// The sub register index of the definition.
+ unsigned DefSubReg;
+ /// The register where the value can be found.
+ unsigned Reg;
+ /// Specifiy whether or not the value tracking looks through
+ /// complex instructions. When this is false, the value tracker
+ /// bails on everything that is not a copy or a bitcast.
+ ///
+ /// Note: This could have been implemented as a specialized version of
+ /// the ValueTracker class but that would have complicated the code of
+ /// the users of this class.
+ bool UseAdvancedTracking;
+ /// MachineRegisterInfo used to perform tracking.
+ const MachineRegisterInfo &MRI;
+ /// Optional TargetInstrInfo used to perform some complex
+ /// tracking.
+ const TargetInstrInfo *TII;
+
+ /// \brief Dispatcher to the right underlying implementation of
+ /// getNextSource.
+ bool getNextSourceImpl(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for Copy instructions.
+ bool getNextSourceFromCopy(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for Bitcast instructions.
+ bool getNextSourceFromBitcast(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for RegSequence
+ /// instructions.
+ bool getNextSourceFromRegSequence(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for InsertSubreg
+ /// instructions.
+ bool getNextSourceFromInsertSubreg(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for ExtractSubreg
+ /// instructions.
+ bool getNextSourceFromExtractSubreg(unsigned &SrcReg, unsigned &SrcSubReg);
+ /// \brief Specialized version of getNextSource for SubregToReg
+ /// instructions.
+ bool getNextSourceFromSubregToReg(unsigned &SrcReg, unsigned &SrcSubReg);
+
+ public:
+ /// \brief Create a ValueTracker instance for the value defined by \p Reg.
+ /// \p DefSubReg represents the sub register index the value tracker will
+ /// track. It does not need to match the sub register index used in the
+ /// definition of \p Reg.
+ /// \p UseAdvancedTracking specifies whether or not the value tracker looks
+ /// through complex instructions. By default (false), it handles only copy
+ /// and bitcast instructions.
+ /// If \p Reg is a physical register, a value tracker constructed with
+ /// this constructor will not find any alternative source.
+ /// Indeed, when \p Reg is a physical register that constructor does not
+ /// know which definition of \p Reg it should track.
+ /// Use the next constructor to track a physical register.
+ ValueTracker(unsigned Reg, unsigned DefSubReg,
+ const MachineRegisterInfo &MRI,
+ bool UseAdvancedTracking = false,
+ const TargetInstrInfo *TII = nullptr)
+ : Def(nullptr), DefIdx(0), DefSubReg(DefSubReg), Reg(Reg),
+ UseAdvancedTracking(UseAdvancedTracking), MRI(MRI), TII(TII) {
+ if (!TargetRegisterInfo::isPhysicalRegister(Reg)) {
+ Def = MRI.getVRegDef(Reg);
+ DefIdx = MRI.def_begin(Reg).getOperandNo();
+ }
+ }
+
+ /// \brief Create a ValueTracker instance for the value defined by
+ /// the pair \p MI, \p DefIdx.
+ /// Unlike the other constructor, the value tracker produced by this one
+ /// may be able to find a new source when the definition is a physical
+ /// register.
+ /// This could be useful to rewrite target specific instructions into
+ /// generic copy instructions.
+ ValueTracker(const MachineInstr &MI, unsigned DefIdx, unsigned DefSubReg,
+ const MachineRegisterInfo &MRI,
+ bool UseAdvancedTracking = false,
+ const TargetInstrInfo *TII = nullptr)
+ : Def(&MI), DefIdx(DefIdx), DefSubReg(DefSubReg),
+ UseAdvancedTracking(UseAdvancedTracking), MRI(MRI), TII(TII) {
+ assert(DefIdx < Def->getDesc().getNumDefs() &&
+ Def->getOperand(DefIdx).isReg() && "Invalid definition");
+ Reg = Def->getOperand(DefIdx).getReg();
+ }
+
+ /// \brief Following the use-def chain, get the next available source
+ /// for the tracked value.
+ /// When the returned value is not nullptr, \p SrcReg gives the register
+ /// that contain the tracked value.
+ /// \note The sub register index returned in \p SrcSubReg must be used
+ /// on \p SrcReg to access the actual value.
+ /// \return Unless the returned value is nullptr (i.e., no source found),
+ /// \p SrcReg gives the register of the next source used in the returned
+ /// instruction and \p SrcSubReg the sub-register index to be used on that
+ /// source to get the tracked value. When nullptr is returned, no
+ /// alternative source has been found.
+ const MachineInstr *getNextSource(unsigned &SrcReg, unsigned &SrcSubReg);
+
+ /// \brief Get the last register where the initial value can be found.
+ /// Initially this is the register of the definition.
+ /// Then, after each successful call to getNextSource, this is the
+ /// register of the last source.
+ unsigned getReg() const { return Reg; }
};
}
/// debug uses.
bool PeepholeOptimizer::
optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
- SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
+ SmallPtrSetImpl<MachineInstr*> &LocalMIs) {
unsigned SrcReg, DstReg, SubIdx;
if (!TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx))
return false;
// Ensure DstReg can get a register class that actually supports
// sub-registers. Don't change the class until we commit.
const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
- DstRC = TM->getRegisterInfo()->getSubClassWithSubReg(DstRC, SubIdx);
+ DstRC = TRI->getSubClassWithSubReg(DstRC, SubIdx);
if (!DstRC)
return false;
// register.
// If UseSrcSubIdx is Set, SubIdx also applies to SrcReg, and only uses of
// SrcReg:SubIdx should be replaced.
- bool UseSrcSubIdx = TM->getRegisterInfo()->
- getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != nullptr;
+ bool UseSrcSubIdx =
+ TRI->getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != nullptr;
// The source has other uses. See if we can replace the other uses with use of
// the result of the extension.
return TRI.getCommonSubClass(DefRC, SrcRC) != nullptr;
}
-/// \brief Get the index of the definition and source for \p Copy
-/// instruction.
-/// \pre Copy.isCopy() or Copy.isBitcast().
-/// \return True if the Copy instruction has only one register source
-/// and one register definition. Otherwise, \p DefIdx and \p SrcIdx
-/// are invalid.
-static bool getCopyOrBitcastDefUseIdx(const MachineInstr &Copy,
- unsigned &DefIdx, unsigned &SrcIdx) {
- assert((Copy.isCopy() || Copy.isBitcast()) && "Wrong operation type.");
- if (Copy.isCopy()) {
- // Copy instruction are supposed to be: Def = Src.
- if (Copy.getDesc().getNumOperands() != 2)
- return false;
- DefIdx = 0;
- SrcIdx = 1;
- assert(Copy.getOperand(DefIdx).isDef() && "Use comes before def!");
- return true;
- }
- // Bitcast case.
- // Bitcasts with more than one def are not supported.
- if (Copy.getDesc().getNumDefs() != 1)
+/// \brief Try to find the next source that share the same register file
+/// for the value defined by \p Reg and \p SubReg.
+/// When true is returned, \p Reg and \p SubReg are updated with the
+/// register number and sub-register index of the new source.
+/// \return False if no alternative sources are available. True otherwise.
+bool PeepholeOptimizer::findNextSource(unsigned &Reg, unsigned &SubReg) {
+ // Do not try to find a new source for a physical register.
+ // So far we do not have any motivating example for doing that.
+ // Thus, instead of maintaining untested code, we will revisit that if
+ // that changes at some point.
+ if (TargetRegisterInfo::isPhysicalRegister(Reg))
return false;
- // Initialize SrcIdx to an undefined operand.
- SrcIdx = Copy.getDesc().getNumOperands();
- for (unsigned OpIdx = 0, EndOpIdx = SrcIdx; OpIdx != EndOpIdx; ++OpIdx) {
- const MachineOperand &MO = Copy.getOperand(OpIdx);
- if (!MO.isReg() || !MO.getReg())
- continue;
- if (MO.isDef())
- DefIdx = OpIdx;
- else if (SrcIdx != EndOpIdx)
- // Multiple sources?
- return false;
- SrcIdx = OpIdx;
- }
- return true;
-}
-/// \brief Optimize a copy or bitcast instruction to avoid cross
-/// register bank copy. The optimization looks through a chain of
-/// copies and try to find a source that has a compatible register
-/// class.
-/// Two register classes are considered to be compatible if they share
-/// the same register bank.
-/// New copies issued by this optimization are register allocator
-/// friendly. This optimization does not remove any copy as it may
-/// overconstraint the register allocator, but replaces some when
-/// possible.
-/// \pre \p MI is a Copy (MI->isCopy() is true)
-/// \return True, when \p MI has been optimized. In that case, \p MI has
-/// been removed from its parent.
-bool PeepholeOptimizer::optimizeCopyOrBitcast(MachineInstr *MI) {
- unsigned DefIdx, SrcIdx;
- if (!MI || !getCopyOrBitcastDefUseIdx(*MI, DefIdx, SrcIdx))
- return false;
-
- const MachineOperand &MODef = MI->getOperand(DefIdx);
- assert(MODef.isReg() && "Copies must be between registers.");
- unsigned Def = MODef.getReg();
-
- if (TargetRegisterInfo::isPhysicalRegister(Def))
- return false;
-
- const TargetRegisterClass *DefRC = MRI->getRegClass(Def);
- unsigned DefSubReg = MODef.getSubReg();
+ const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);
+ unsigned DefSubReg = SubReg;
unsigned Src;
unsigned SrcSubReg;
bool ShouldRewrite = false;
- MachineInstr *Copy = MI;
- const TargetRegisterInfo &TRI = *TM->getRegisterInfo();
- // Follow the chain of copies until we reach the top or find a
- // more suitable source.
+ // Follow the chain of copies until we reach the top of the use-def chain
+ // or find a more suitable source.
+ ValueTracker ValTracker(Reg, DefSubReg, *MRI, !DisableAdvCopyOpt, TII);
do {
- unsigned CopyDefIdx, CopySrcIdx;
- if (!getCopyOrBitcastDefUseIdx(*Copy, CopyDefIdx, CopySrcIdx))
+ unsigned CopySrcReg, CopySrcSubReg;
+ if (!ValTracker.getNextSource(CopySrcReg, CopySrcSubReg))
break;
- const MachineOperand &MO = Copy->getOperand(CopySrcIdx);
- assert(MO.isReg() && "Copies must be between registers.");
- Src = MO.getReg();
-
+ Src = CopySrcReg;
+ SrcSubReg = CopySrcSubReg;
+
+ // Do not extend the live-ranges of physical registers as they add
+ // constraints to the register allocator.
+ // Moreover, if we want to extend the live-range of a physical register,
+ // unlike SSA virtual register, we will have to check that they are not
+ // redefine before the related use.
if (TargetRegisterInfo::isPhysicalRegister(Src))
break;
const TargetRegisterClass *SrcRC = MRI->getRegClass(Src);
- SrcSubReg = MO.getSubReg();
// If this source does not incur a cross register bank copy, use it.
- ShouldRewrite = shareSameRegisterFile(TRI, DefRC, DefSubReg, SrcRC,
+ ShouldRewrite = shareSameRegisterFile(*TRI, DefRC, DefSubReg, SrcRC,
SrcSubReg);
- // Follow the chain of copies: get the definition of Src.
- Copy = MRI->getVRegDef(Src);
- } while (!ShouldRewrite && Copy && (Copy->isCopy() || Copy->isBitcast()));
+ } while (!ShouldRewrite);
// If we did not find a more suitable source, there is nothing to optimize.
- if (!ShouldRewrite || Src == MI->getOperand(SrcIdx).getReg())
+ if (!ShouldRewrite || Src == Reg)
+ return false;
+
+ Reg = Src;
+ SubReg = SrcSubReg;
+ return true;
+}
+
+namespace {
+/// \brief Helper class to rewrite the arguments of a copy-like instruction.
+class CopyRewriter {
+protected:
+ /// The copy-like instruction.
+ MachineInstr &CopyLike;
+ /// The index of the source being rewritten.
+ unsigned CurrentSrcIdx;
+
+public:
+ CopyRewriter(MachineInstr &MI) : CopyLike(MI), CurrentSrcIdx(0) {}
+
+ virtual ~CopyRewriter() {}
+
+ /// \brief Get the next rewritable source (SrcReg, SrcSubReg) and
+ /// the related value that it affects (TrackReg, TrackSubReg).
+ /// A source is considered rewritable if its register class and the
+ /// register class of the related TrackReg may not be register
+ /// coalescer friendly. In other words, given a copy-like instruction
+ /// not all the arguments may be returned at rewritable source, since
+ /// some arguments are none to be register coalescer friendly.
+ ///
+ /// Each call of this method moves the current source to the next
+ /// rewritable source.
+ /// For instance, let CopyLike be the instruction to rewrite.
+ /// CopyLike has one definition and one source:
+ /// dst.dstSubIdx = CopyLike src.srcSubIdx.
+ ///
+ /// The first call will give the first rewritable source, i.e.,
+ /// the only source this instruction has:
+ /// (SrcReg, SrcSubReg) = (src, srcSubIdx).
+ /// This source defines the whole definition, i.e.,
+ /// (TrackReg, TrackSubReg) = (dst, dstSubIdx).
+ ///
+ /// The second and subsequent calls will return false, has there is only one
+ /// rewritable source.
+ ///
+ /// \return True if a rewritable source has been found, false otherwise.
+ /// The output arguments are valid if and only if true is returned.
+ virtual bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg,
+ unsigned &TrackReg,
+ unsigned &TrackSubReg) {
+ // If CurrentSrcIdx == 1, this means this function has already been
+ // called once. CopyLike has one defintiion and one argument, thus,
+ // there is nothing else to rewrite.
+ if (!CopyLike.isCopy() || CurrentSrcIdx == 1)
+ return false;
+ // This is the first call to getNextRewritableSource.
+ // Move the CurrentSrcIdx to remember that we made that call.
+ CurrentSrcIdx = 1;
+ // The rewritable source is the argument.
+ const MachineOperand &MOSrc = CopyLike.getOperand(1);
+ SrcReg = MOSrc.getReg();
+ SrcSubReg = MOSrc.getSubReg();
+ // What we track are the alternative sources of the definition.
+ const MachineOperand &MODef = CopyLike.getOperand(0);
+ TrackReg = MODef.getReg();
+ TrackSubReg = MODef.getSubReg();
+ return true;
+ }
+
+ /// \brief Rewrite the current source with \p NewReg and \p NewSubReg
+ /// if possible.
+ /// \return True if the rewritting was possible, false otherwise.
+ virtual bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) {
+ if (!CopyLike.isCopy() || CurrentSrcIdx != 1)
+ return false;
+ MachineOperand &MOSrc = CopyLike.getOperand(CurrentSrcIdx);
+ MOSrc.setReg(NewReg);
+ MOSrc.setSubReg(NewSubReg);
+ return true;
+ }
+};
+
+/// \brief Specialized rewriter for INSERT_SUBREG instruction.
+class InsertSubregRewriter : public CopyRewriter {
+public:
+ InsertSubregRewriter(MachineInstr &MI) : CopyRewriter(MI) {
+ assert(MI.isInsertSubreg() && "Invalid instruction");
+ }
+
+ /// \brief See CopyRewriter::getNextRewritableSource.
+ /// Here CopyLike has the following form:
+ /// dst = INSERT_SUBREG Src1, Src2.src2SubIdx, subIdx.
+ /// Src1 has the same register class has dst, hence, there is
+ /// nothing to rewrite.
+ /// Src2.src2SubIdx, may not be register coalescer friendly.
+ /// Therefore, the first call to this method returns:
+ /// (SrcReg, SrcSubReg) = (Src2, src2SubIdx).
+ /// (TrackReg, TrackSubReg) = (dst, subIdx).
+ ///
+ /// Subsequence calls will return false.
+ bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg,
+ unsigned &TrackReg,
+ unsigned &TrackSubReg) override {
+ // If we already get the only source we can rewrite, return false.
+ if (CurrentSrcIdx == 2)
+ return false;
+ // We are looking at v2 = INSERT_SUBREG v0, v1, sub0.
+ CurrentSrcIdx = 2;
+ const MachineOperand &MOInsertedReg = CopyLike.getOperand(2);
+ SrcReg = MOInsertedReg.getReg();
+ SrcSubReg = MOInsertedReg.getSubReg();
+ const MachineOperand &MODef = CopyLike.getOperand(0);
+
+ // We want to track something that is compatible with the
+ // partial definition.
+ TrackReg = MODef.getReg();
+ if (MODef.getSubReg())
+ // Bails if we have to compose sub-register indices.
+ return false;
+ TrackSubReg = (unsigned)CopyLike.getOperand(3).getImm();
+ return true;
+ }
+ bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override {
+ if (CurrentSrcIdx != 2)
+ return false;
+ // We are rewriting the inserted reg.
+ MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx);
+ MO.setReg(NewReg);
+ MO.setSubReg(NewSubReg);
+ return true;
+ }
+};
+
+/// \brief Specialized rewriter for EXTRACT_SUBREG instruction.
+class ExtractSubregRewriter : public CopyRewriter {
+ const TargetInstrInfo &TII;
+
+public:
+ ExtractSubregRewriter(MachineInstr &MI, const TargetInstrInfo &TII)
+ : CopyRewriter(MI), TII(TII) {
+ assert(MI.isExtractSubreg() && "Invalid instruction");
+ }
+
+ /// \brief See CopyRewriter::getNextRewritableSource.
+ /// Here CopyLike has the following form:
+ /// dst.dstSubIdx = EXTRACT_SUBREG Src, subIdx.
+ /// There is only one rewritable source: Src.subIdx,
+ /// which defines dst.dstSubIdx.
+ bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg,
+ unsigned &TrackReg,
+ unsigned &TrackSubReg) override {
+ // If we already get the only source we can rewrite, return false.
+ if (CurrentSrcIdx == 1)
+ return false;
+ // We are looking at v1 = EXTRACT_SUBREG v0, sub0.
+ CurrentSrcIdx = 1;
+ const MachineOperand &MOExtractedReg = CopyLike.getOperand(1);
+ SrcReg = MOExtractedReg.getReg();
+ // If we have to compose sub-register indices, bails out.
+ if (MOExtractedReg.getSubReg())
+ return false;
+
+ SrcSubReg = CopyLike.getOperand(2).getImm();
+
+ // We want to track something that is compatible with the definition.
+ const MachineOperand &MODef = CopyLike.getOperand(0);
+ TrackReg = MODef.getReg();
+ TrackSubReg = MODef.getSubReg();
+ return true;
+ }
+
+ bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override {
+ // The only source we can rewrite is the input register.
+ if (CurrentSrcIdx != 1)
+ return false;
+
+ CopyLike.getOperand(CurrentSrcIdx).setReg(NewReg);
+
+ // If we find a source that does not require to extract something,
+ // rewrite the operation with a copy.
+ if (!NewSubReg) {
+ // Move the current index to an invalid position.
+ // We do not want another call to this method to be able
+ // to do any change.
+ CurrentSrcIdx = -1;
+ // Rewrite the operation as a COPY.
+ // Get rid of the sub-register index.
+ CopyLike.RemoveOperand(2);
+ // Morph the operation into a COPY.
+ CopyLike.setDesc(TII.get(TargetOpcode::COPY));
+ return true;
+ }
+ CopyLike.getOperand(CurrentSrcIdx + 1).setImm(NewSubReg);
+ return true;
+ }
+};
+
+/// \brief Specialized rewriter for REG_SEQUENCE instruction.
+class RegSequenceRewriter : public CopyRewriter {
+public:
+ RegSequenceRewriter(MachineInstr &MI) : CopyRewriter(MI) {
+ assert(MI.isRegSequence() && "Invalid instruction");
+ }
+
+ /// \brief See CopyRewriter::getNextRewritableSource.
+ /// Here CopyLike has the following form:
+ /// dst = REG_SEQUENCE Src1.src1SubIdx, subIdx1, Src2.src2SubIdx, subIdx2.
+ /// Each call will return a different source, walking all the available
+ /// source.
+ ///
+ /// The first call returns:
+ /// (SrcReg, SrcSubReg) = (Src1, src1SubIdx).
+ /// (TrackReg, TrackSubReg) = (dst, subIdx1).
+ ///
+ /// The second call returns:
+ /// (SrcReg, SrcSubReg) = (Src2, src2SubIdx).
+ /// (TrackReg, TrackSubReg) = (dst, subIdx2).
+ ///
+ /// And so on, until all the sources have been traversed, then
+ /// it returns false.
+ bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg,
+ unsigned &TrackReg,
+ unsigned &TrackSubReg) override {
+ // We are looking at v0 = REG_SEQUENCE v1, sub1, v2, sub2, etc.
+
+ // If this is the first call, move to the first argument.
+ if (CurrentSrcIdx == 0) {
+ CurrentSrcIdx = 1;
+ } else {
+ // Otherwise, move to the next argument and check that it is valid.
+ CurrentSrcIdx += 2;
+ if (CurrentSrcIdx >= CopyLike.getNumOperands())
+ return false;
+ }
+ const MachineOperand &MOInsertedReg = CopyLike.getOperand(CurrentSrcIdx);
+ SrcReg = MOInsertedReg.getReg();
+ // If we have to compose sub-register indices, bails out.
+ if ((SrcSubReg = MOInsertedReg.getSubReg()))
+ return false;
+
+ // We want to track something that is compatible with the related
+ // partial definition.
+ TrackSubReg = CopyLike.getOperand(CurrentSrcIdx + 1).getImm();
+
+ const MachineOperand &MODef = CopyLike.getOperand(0);
+ TrackReg = MODef.getReg();
+ // If we have to compose sub-registers, bails.
+ return MODef.getSubReg() == 0;
+ }
+
+ bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override {
+ // We cannot rewrite out of bound operands.
+ // Moreover, rewritable sources are at odd positions.
+ if ((CurrentSrcIdx & 1) != 1 || CurrentSrcIdx > CopyLike.getNumOperands())
+ return false;
+
+ MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx);
+ MO.setReg(NewReg);
+ MO.setSubReg(NewSubReg);
+ return true;
+ }
+};
+} // End namespace.
+
+/// \brief Get the appropriated CopyRewriter for \p MI.
+/// \return A pointer to a dynamically allocated CopyRewriter or nullptr
+/// if no rewriter works for \p MI.
+static CopyRewriter *getCopyRewriter(MachineInstr &MI,
+ const TargetInstrInfo &TII) {
+ switch (MI.getOpcode()) {
+ default:
+ return nullptr;
+ case TargetOpcode::COPY:
+ return new CopyRewriter(MI);
+ case TargetOpcode::INSERT_SUBREG:
+ return new InsertSubregRewriter(MI);
+ case TargetOpcode::EXTRACT_SUBREG:
+ return new ExtractSubregRewriter(MI, TII);
+ case TargetOpcode::REG_SEQUENCE:
+ return new RegSequenceRewriter(MI);
+ }
+ llvm_unreachable(nullptr);
+}
+
+/// \brief Optimize generic copy instructions to avoid cross
+/// register bank copy. The optimization looks through a chain of
+/// copies and tries to find a source that has a compatible register
+/// class.
+/// Two register classes are considered to be compatible if they share
+/// the same register bank.
+/// New copies issued by this optimization are register allocator
+/// friendly. This optimization does not remove any copy as it may
+/// overconstraint the register allocator, but replaces some operands
+/// when possible.
+/// \pre isCoalescableCopy(*MI) is true.
+/// \return True, when \p MI has been rewritten. False otherwise.
+bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr *MI) {
+ assert(MI && isCoalescableCopy(*MI) && "Invalid argument");
+ assert(MI->getDesc().getNumDefs() == 1 &&
+ "Coalescer can understand multiple defs?!");
+ const MachineOperand &MODef = MI->getOperand(0);
+ // Do not rewrite physical definitions.
+ if (TargetRegisterInfo::isPhysicalRegister(MODef.getReg()))
return false;
- // Rewrite the copy to avoid a cross register bank penalty.
- unsigned NewVR = TargetRegisterInfo::isPhysicalRegister(Def) ? Def :
- MRI->createVirtualRegister(DefRC);
- MachineInstr *NewCopy = BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
- TII->get(TargetOpcode::COPY), NewVR)
- .addReg(Src, 0, SrcSubReg);
- NewCopy->getOperand(0).setSubReg(DefSubReg);
+ bool Changed = false;
+ // Get the right rewriter for the current copy.
+ std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII));
+ // If none exists, bails out.
+ if (!CpyRewriter)
+ return false;
+ // Rewrite each rewritable source.
+ unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg;
+ while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg,
+ TrackSubReg)) {
+ unsigned NewSrc = TrackReg;
+ unsigned NewSubReg = TrackSubReg;
+ // Try to find a more suitable source.
+ // If we failed to do so, or get the actual source,
+ // move to the next source.
+ if (!findNextSource(NewSrc, NewSubReg) || SrcReg == NewSrc)
+ continue;
+ // Rewrite source.
+ if (CpyRewriter->RewriteCurrentSource(NewSrc, NewSubReg)) {
+ // We may have extended the live-range of NewSrc, account for that.
+ MRI->clearKillFlags(NewSrc);
+ Changed = true;
+ }
+ }
+ // TODO: We could have a clean-up method to tidy the instruction.
+ // E.g., v0 = INSERT_SUBREG v1, v1.sub0, sub0
+ // => v0 = COPY v1
+ // Currently we haven't seen motivating example for that and we
+ // want to avoid untested code.
+ NumRewrittenCopies += Changed == true;
+ return Changed;
+}
+
+/// \brief Optimize copy-like instructions to create
+/// register coalescer friendly instruction.
+/// The optimization tries to kill-off the \p MI by looking
+/// through a chain of copies to find a source that has a compatible
+/// register class.
+/// If such a source is found, it replace \p MI by a generic COPY
+/// operation.
+/// \pre isUncoalescableCopy(*MI) is true.
+/// \return True, when \p MI has been optimized. In that case, \p MI has
+/// been removed from its parent.
+/// All COPY instructions created, are inserted in \p LocalMIs.
+bool PeepholeOptimizer::optimizeUncoalescableCopy(
+ MachineInstr *MI, SmallPtrSetImpl<MachineInstr *> &LocalMIs) {
+ assert(MI && isUncoalescableCopy(*MI) && "Invalid argument");
+
+ // Check if we can rewrite all the values defined by this instruction.
+ SmallVector<
+ std::pair<TargetInstrInfo::RegSubRegPair, TargetInstrInfo::RegSubRegPair>,
+ 4> RewritePairs;
+ for (const MachineOperand &MODef : MI->defs()) {
+ if (MODef.isDead())
+ // We can ignore those.
+ continue;
+
+ // If a physical register is here, this is probably for a good reason.
+ // Do not rewrite that.
+ if (TargetRegisterInfo::isPhysicalRegister(MODef.getReg()))
+ return false;
- MRI->replaceRegWith(Def, NewVR);
- MRI->clearKillFlags(NewVR);
+ // If we do not know how to rewrite this definition, there is no point
+ // in trying to kill this instruction.
+ TargetInstrInfo::RegSubRegPair Def(MODef.getReg(), MODef.getSubReg());
+ TargetInstrInfo::RegSubRegPair Src = Def;
+ if (!findNextSource(Src.Reg, Src.SubReg))
+ return false;
+ RewritePairs.push_back(std::make_pair(Def, Src));
+ }
+ // The change is possible for all defs, do it.
+ for (const auto &PairDefSrc : RewritePairs) {
+ const auto &Def = PairDefSrc.first;
+ const auto &Src = PairDefSrc.second;
+ // Rewrite the "copy" in a way the register coalescer understands.
+ assert(!TargetRegisterInfo::isPhysicalRegister(Def.Reg) &&
+ "We do not rewrite physical registers");
+ const TargetRegisterClass *DefRC = MRI->getRegClass(Def.Reg);
+ unsigned NewVR = MRI->createVirtualRegister(DefRC);
+ MachineInstr *NewCopy = BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
+ TII->get(TargetOpcode::COPY),
+ NewVR).addReg(Src.Reg, 0, Src.SubReg);
+ NewCopy->getOperand(0).setSubReg(Def.SubReg);
+ if (Def.SubReg)
+ NewCopy->getOperand(0).setIsUndef();
+ LocalMIs.insert(NewCopy);
+ MRI->replaceRegWith(Def.Reg, NewVR);
+ MRI->clearKillFlags(NewVR);
+ // We extended the lifetime of Src.
+ // Clear the kill flags to account for that.
+ MRI->clearKillFlags(Src.Reg);
+ }
+ // MI is now dead.
MI->eraseFromParent();
- ++NumCopiesBitcasts;
+ ++NumUncoalescableCopies;
return true;
}
return false;
}
-bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
- if (skipOptnoneFunction(*MF.getFunction()))
+bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &mf) {
+ if (skipOptnoneFunction(*mf.getFunction()))
return false;
DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n");
- DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n');
+ DEBUG(dbgs() << "********** Function: " << mf.getName() << '\n');
if (DisablePeephole)
return false;
- TM = &MF.getTarget();
- TII = TM->getInstrInfo();
- MRI = &MF.getRegInfo();
+ MF = &mf;
+ TII = MF->getSubtarget().getInstrInfo();
+ TRI = MF->getSubtarget().getRegisterInfo();
+ MRI = &MF->getRegInfo();
DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : nullptr;
bool Changed = false;
- for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+ for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
bool SeenMoveImm = false;
- SmallPtrSet<MachineInstr*, 8> LocalMIs;
+ SmallPtrSet<MachineInstr*, 16> LocalMIs;
SmallSet<unsigned, 4> ImmDefRegs;
DenseMap<unsigned, MachineInstr*> ImmDefMIs;
SmallSet<unsigned, 16> FoldAsLoadDefCandidates;
if (MI->mayStore() || MI->isCall())
FoldAsLoadDefCandidates.clear();
- if (((MI->isBitcast() || MI->isCopy()) && optimizeCopyOrBitcast(MI)) ||
+ if ((isUncoalescableCopy(*MI) &&
+ optimizeUncoalescableCopy(MI, LocalMIs)) ||
(MI->isCompare() && optimizeCmpInstr(MI, MBB)) ||
(MI->isSelect() && optimizeSelect(MI))) {
// MI is deleted.
continue;
}
+ if (isCoalescableCopy(*MI) && optimizeCoalescableCopy(MI)) {
+ // MI is just rewritten.
+ Changed = true;
+ continue;
+ }
+
if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
SeenMoveImm = true;
} else {
return Changed;
}
+
+bool ValueTracker::getNextSourceFromCopy(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert(Def->isCopy() && "Invalid definition");
+ // Copy instruction are supposed to be: Def = Src.
+ // If someone breaks this assumption, bad things will happen everywhere.
+ assert(Def->getNumOperands() == 2 && "Invalid number of operands");
+
+ if (Def->getOperand(DefIdx).getSubReg() != DefSubReg)
+ // If we look for a different subreg, it means we want a subreg of src.
+ // Bails as we do not support composing subreg yet.
+ return false;
+ // Otherwise, we want the whole source.
+ const MachineOperand &Src = Def->getOperand(1);
+ SrcReg = Src.getReg();
+ SrcSubReg = Src.getSubReg();
+ return true;
+}
+
+bool ValueTracker::getNextSourceFromBitcast(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert(Def->isBitcast() && "Invalid definition");
+
+ // Bail if there are effects that a plain copy will not expose.
+ if (Def->hasUnmodeledSideEffects())
+ return false;
+
+ // Bitcasts with more than one def are not supported.
+ if (Def->getDesc().getNumDefs() != 1)
+ return false;
+ if (Def->getOperand(DefIdx).getSubReg() != DefSubReg)
+ // If we look for a different subreg, it means we want a subreg of the src.
+ // Bails as we do not support composing subreg yet.
+ return false;
+
+ unsigned SrcIdx = Def->getNumOperands();
+ for (unsigned OpIdx = DefIdx + 1, EndOpIdx = SrcIdx; OpIdx != EndOpIdx;
+ ++OpIdx) {
+ const MachineOperand &MO = Def->getOperand(OpIdx);
+ if (!MO.isReg() || !MO.getReg())
+ continue;
+ assert(!MO.isDef() && "We should have skipped all the definitions by now");
+ if (SrcIdx != EndOpIdx)
+ // Multiple sources?
+ return false;
+ SrcIdx = OpIdx;
+ }
+ const MachineOperand &Src = Def->getOperand(SrcIdx);
+ SrcReg = Src.getReg();
+ SrcSubReg = Src.getSubReg();
+ return true;
+}
+
+bool ValueTracker::getNextSourceFromRegSequence(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert((Def->isRegSequence() || Def->isRegSequenceLike()) &&
+ "Invalid definition");
+
+ if (Def->getOperand(DefIdx).getSubReg())
+ // If we are composing subreg, bails out.
+ // The case we are checking is Def.<subreg> = REG_SEQUENCE.
+ // This should almost never happen as the SSA property is tracked at
+ // the register level (as opposed to the subreg level).
+ // I.e.,
+ // Def.sub0 =
+ // Def.sub1 =
+ // is a valid SSA representation for Def.sub0 and Def.sub1, but not for
+ // Def. Thus, it must not be generated.
+ // However, some code could theoretically generates a single
+ // Def.sub0 (i.e, not defining the other subregs) and we would
+ // have this case.
+ // If we can ascertain (or force) that this never happens, we could
+ // turn that into an assertion.
+ return false;
+
+ if (!TII)
+ // We could handle the REG_SEQUENCE here, but we do not want to
+ // duplicate the code from the generic TII.
+ return false;
+
+ SmallVector<TargetInstrInfo::RegSubRegPairAndIdx, 8> RegSeqInputRegs;
+ if (!TII->getRegSequenceInputs(*Def, DefIdx, RegSeqInputRegs))
+ return false;
+
+ // We are looking at:
+ // Def = REG_SEQUENCE v0, sub0, v1, sub1, ...
+ // Check if one of the operand defines the subreg we are interested in.
+ for (auto &RegSeqInput : RegSeqInputRegs) {
+ if (RegSeqInput.SubIdx == DefSubReg) {
+ if (RegSeqInput.SubReg)
+ // Bails if we have to compose sub registers.
+ return false;
+
+ SrcReg = RegSeqInput.Reg;
+ SrcSubReg = RegSeqInput.SubReg;
+ return true;
+ }
+ }
+
+ // If the subreg we are tracking is super-defined by another subreg,
+ // we could follow this value. However, this would require to compose
+ // the subreg and we do not do that for now.
+ return false;
+}
+
+bool ValueTracker::getNextSourceFromInsertSubreg(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert((Def->isInsertSubreg() || Def->isInsertSubregLike()) &&
+ "Invalid definition");
+
+ if (Def->getOperand(DefIdx).getSubReg())
+ // If we are composing subreg, bails out.
+ // Same remark as getNextSourceFromRegSequence.
+ // I.e., this may be turned into an assert.
+ return false;
+
+ if (!TII)
+ // We could handle the REG_SEQUENCE here, but we do not want to
+ // duplicate the code from the generic TII.
+ return false;
+
+ TargetInstrInfo::RegSubRegPair BaseReg;
+ TargetInstrInfo::RegSubRegPairAndIdx InsertedReg;
+ if (!TII->getInsertSubregInputs(*Def, DefIdx, BaseReg, InsertedReg))
+ return false;
+
+ // We are looking at:
+ // Def = INSERT_SUBREG v0, v1, sub1
+ // There are two cases:
+ // 1. DefSubReg == sub1, get v1.
+ // 2. DefSubReg != sub1, the value may be available through v0.
+
+ // #1 Check if the inserted register matches the required sub index.
+ if (InsertedReg.SubIdx == DefSubReg) {
+ SrcReg = InsertedReg.Reg;
+ SrcSubReg = InsertedReg.SubReg;
+ return true;
+ }
+ // #2 Otherwise, if the sub register we are looking for is not partial
+ // defined by the inserted element, we can look through the main
+ // register (v0).
+ const MachineOperand &MODef = Def->getOperand(DefIdx);
+ // If the result register (Def) and the base register (v0) do not
+ // have the same register class or if we have to compose
+ // subregisters, bails out.
+ if (MRI.getRegClass(MODef.getReg()) != MRI.getRegClass(BaseReg.Reg) ||
+ BaseReg.SubReg)
+ return false;
+
+ // Get the TRI and check if the inserted sub-register overlaps with the
+ // sub-register we are tracking.
+ const TargetRegisterInfo *TRI = MRI.getTargetRegisterInfo();
+ if (!TRI ||
+ (TRI->getSubRegIndexLaneMask(DefSubReg) &
+ TRI->getSubRegIndexLaneMask(InsertedReg.SubIdx)) != 0)
+ return false;
+ // At this point, the value is available in v0 via the same subreg
+ // we used for Def.
+ SrcReg = BaseReg.Reg;
+ SrcSubReg = DefSubReg;
+ return true;
+}
+
+bool ValueTracker::getNextSourceFromExtractSubreg(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert((Def->isExtractSubreg() ||
+ Def->isExtractSubregLike()) && "Invalid definition");
+ // We are looking at:
+ // Def = EXTRACT_SUBREG v0, sub0
+
+ // Bails if we have to compose sub registers.
+ // Indeed, if DefSubReg != 0, we would have to compose it with sub0.
+ if (DefSubReg)
+ return false;
+
+ if (!TII)
+ // We could handle the EXTRACT_SUBREG here, but we do not want to
+ // duplicate the code from the generic TII.
+ return false;
+
+ TargetInstrInfo::RegSubRegPairAndIdx ExtractSubregInputReg;
+ if (!TII->getExtractSubregInputs(*Def, DefIdx, ExtractSubregInputReg))
+ return false;
+
+ // Bails if we have to compose sub registers.
+ // Likewise, if v0.subreg != 0, we would have to compose v0.subreg with sub0.
+ if (ExtractSubregInputReg.SubReg)
+ return false;
+ // Otherwise, the value is available in the v0.sub0.
+ SrcReg = ExtractSubregInputReg.Reg;
+ SrcSubReg = ExtractSubregInputReg.SubIdx;
+ return true;
+}
+
+bool ValueTracker::getNextSourceFromSubregToReg(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ assert(Def->isSubregToReg() && "Invalid definition");
+ // We are looking at:
+ // Def = SUBREG_TO_REG Imm, v0, sub0
+
+ // Bails if we have to compose sub registers.
+ // If DefSubReg != sub0, we would have to check that all the bits
+ // we track are included in sub0 and if yes, we would have to
+ // determine the right subreg in v0.
+ if (DefSubReg != Def->getOperand(3).getImm())
+ return false;
+ // Bails if we have to compose sub registers.
+ // Likewise, if v0.subreg != 0, we would have to compose it with sub0.
+ if (Def->getOperand(2).getSubReg())
+ return false;
+
+ SrcReg = Def->getOperand(2).getReg();
+ SrcSubReg = Def->getOperand(3).getImm();
+ return true;
+}
+
+bool ValueTracker::getNextSourceImpl(unsigned &SrcReg, unsigned &SrcSubReg) {
+ assert(Def && "This method needs a valid definition");
+
+ assert(
+ (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic()) &&
+ Def->getOperand(DefIdx).isDef() && "Invalid DefIdx");
+ if (Def->isCopy())
+ return getNextSourceFromCopy(SrcReg, SrcSubReg);
+ if (Def->isBitcast())
+ return getNextSourceFromBitcast(SrcReg, SrcSubReg);
+ // All the remaining cases involve "complex" instructions.
+ // Bails if we did not ask for the advanced tracking.
+ if (!UseAdvancedTracking)
+ return false;
+ if (Def->isRegSequence() || Def->isRegSequenceLike())
+ return getNextSourceFromRegSequence(SrcReg, SrcSubReg);
+ if (Def->isInsertSubreg() || Def->isInsertSubregLike())
+ return getNextSourceFromInsertSubreg(SrcReg, SrcSubReg);
+ if (Def->isExtractSubreg() || Def->isExtractSubregLike())
+ return getNextSourceFromExtractSubreg(SrcReg, SrcSubReg);
+ if (Def->isSubregToReg())
+ return getNextSourceFromSubregToReg(SrcReg, SrcSubReg);
+ return false;
+}
+
+const MachineInstr *ValueTracker::getNextSource(unsigned &SrcReg,
+ unsigned &SrcSubReg) {
+ // If we reach a point where we cannot move up in the use-def chain,
+ // there is nothing we can get.
+ if (!Def)
+ return nullptr;
+
+ const MachineInstr *PrevDef = nullptr;
+ // Try to find the next source.
+ if (getNextSourceImpl(SrcReg, SrcSubReg)) {
+ // Update definition, definition index, and subregister for the
+ // next call of getNextSource.
+ // Update the current register.
+ Reg = SrcReg;
+ // Update the return value before moving up in the use-def chain.
+ PrevDef = Def;
+ // If we can still move up in the use-def chain, move to the next
+ // defintion.
+ if (!TargetRegisterInfo::isPhysicalRegister(Reg)) {
+ Def = MRI.getVRegDef(Reg);
+ DefIdx = MRI.def_begin(Reg).getOperandNo();
+ DefSubReg = SrcSubReg;
+ return PrevDef;
+ }
+ }
+ // If we end up here, this means we will not be able to find another source
+ // for the next iteration.
+ // Make sure any new call to getNextSource bails out early by cutting the
+ // use-def chain.
+ Def = nullptr;
+ return PrevDef;
+}
projects / oota-llvm.git / blobdiff