//
//===----------------------------------------------------------------------===//
-#include "InstCombine.h"
+#include "InstCombineInternal.h"
+#include "llvm/ADT/APSInt.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
-#include "llvm/Target/TargetLibraryInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
+// How many times is a select replaced by one of its operands?
+STATISTIC(NumSel, "Number of select opts");
+
+// Initialization Routines
+
static ConstantInt *getOne(Constant *C) {
return ConstantInt::get(cast<IntegerType>(C->getType()), 1);
}
if (ICmpInst::isSigned(Cond))
return nullptr;
- // Look through bitcasts.
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS))
- RHS = BCI->getOperand(0);
+ // Look through bitcasts and addrspacecasts. We do not however want to remove
+ // 0 GEPs.
+ if (!isa<GetElementPtrInst>(RHS))
+ RHS = RHS->stripPointerCasts();
Value *PtrBase = GEPLHS->getOperand(0);
if (DL && PtrBase == RHS && GEPLHS->isInBounds()) {
(GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
PtrBase->stripPointerCasts() ==
GEPRHS->getOperand(0)->stripPointerCasts()) {
+ Value *LOffset = EmitGEPOffset(GEPLHS);
+ Value *ROffset = EmitGEPOffset(GEPRHS);
+
+ // If we looked through an addrspacecast between different sized address
+ // spaces, the LHS and RHS pointers are different sized
+ // integers. Truncate to the smaller one.
+ Type *LHSIndexTy = LOffset->getType();
+ Type *RHSIndexTy = ROffset->getType();
+ if (LHSIndexTy != RHSIndexTy) {
+ if (LHSIndexTy->getPrimitiveSizeInBits() <
+ RHSIndexTy->getPrimitiveSizeInBits()) {
+ ROffset = Builder->CreateTrunc(ROffset, LHSIndexTy);
+ } else
+ LOffset = Builder->CreateTrunc(LOffset, RHSIndexTy);
+ }
+
Value *Cmp = Builder->CreateICmp(ICmpInst::getSignedPredicate(Cond),
- EmitGEPOffset(GEPLHS),
- EmitGEPOffset(GEPRHS));
+ LOffset, ROffset);
return ReplaceInstUsesWith(I, Cmp);
}
}
// If one of the GEPs has all zero indices, recurse.
- bool AllZeros = true;
- for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
- if (!isa<Constant>(GEPLHS->getOperand(i)) ||
- !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
- AllZeros = false;
- break;
- }
- if (AllZeros)
+ if (GEPLHS->hasAllZeroIndices())
return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
ICmpInst::getSwappedPredicate(Cond), I);
// If the other GEP has all zero indices, recurse.
- AllZeros = true;
- for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
- if (!isa<Constant>(GEPRHS->getOperand(i)) ||
- !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
- AllZeros = false;
- break;
- }
- if (AllZeros)
+ if (GEPRHS->hasAllZeroIndices())
return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
Instruction *InstCombiner::FoldICmpAddOpCst(Instruction &ICI,
Value *X, ConstantInt *CI,
ICmpInst::Predicate Pred) {
- // If we have X+0, exit early (simplifying logic below) and let it get folded
- // elsewhere. icmp X+0, X -> icmp X, X
- if (CI->isZero()) {
- bool isTrue = ICmpInst::isTrueWhenEqual(Pred);
- return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue));
- }
-
- // (X+4) == X -> false.
- if (Pred == ICmpInst::ICMP_EQ)
- return ReplaceInstUsesWith(ICI, Builder->getFalse());
-
- // (X+4) != X -> true.
- if (Pred == ICmpInst::ICMP_NE)
- return ReplaceInstUsesWith(ICI, Builder->getTrue());
-
// From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
// so the values can never be equal. Similarly for all other "or equals"
// operators.
return nullptr;
}
+/// FoldICmpCstShrCst - Handle "(icmp eq/ne (ashr/lshr const2, A), const1)" ->
+/// (icmp eq/ne A, Log2(const2/const1)) ->
+/// (icmp eq/ne A, Log2(const2) - Log2(const1)).
+Instruction *InstCombiner::FoldICmpCstShrCst(ICmpInst &I, Value *Op, Value *A,
+ ConstantInt *CI1,
+ ConstantInt *CI2) {
+ assert(I.isEquality() && "Cannot fold icmp gt/lt");
+
+ auto getConstant = [&I, this](bool IsTrue) {
+ if (I.getPredicate() == I.ICMP_NE)
+ IsTrue = !IsTrue;
+ return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), IsTrue));
+ };
+
+ auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
+ if (I.getPredicate() == I.ICMP_NE)
+ Pred = CmpInst::getInversePredicate(Pred);
+ return new ICmpInst(Pred, LHS, RHS);
+ };
+
+ APInt AP1 = CI1->getValue();
+ APInt AP2 = CI2->getValue();
+
+ // Don't bother doing any work for cases which InstSimplify handles.
+ if (AP2 == 0)
+ return nullptr;
+ bool IsAShr = isa<AShrOperator>(Op);
+ if (IsAShr) {
+ if (AP2.isAllOnesValue())
+ return nullptr;
+ if (AP2.isNegative() != AP1.isNegative())
+ return nullptr;
+ if (AP2.sgt(AP1))
+ return nullptr;
+ }
+
+ if (!AP1)
+ // 'A' must be large enough to shift out the highest set bit.
+ return getICmp(I.ICMP_UGT, A,
+ ConstantInt::get(A->getType(), AP2.logBase2()));
+
+ if (AP1 == AP2)
+ return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
+
+ // Get the distance between the highest bit that's set.
+ int Shift;
+ // Both the constants are negative, take their positive to calculate log.
+ if (IsAShr && AP1.isNegative())
+ // Get the ones' complement of AP2 and AP1 when computing the distance.
+ Shift = (~AP2).logBase2() - (~AP1).logBase2();
+ else
+ Shift = AP2.logBase2() - AP1.logBase2();
+
+ if (Shift > 0) {
+ if (IsAShr ? AP1 == AP2.ashr(Shift) : AP1 == AP2.lshr(Shift))
+ return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
+ }
+ // Shifting const2 will never be equal to const1.
+ return getConstant(false);
+}
+
+/// FoldICmpCstShlCst - Handle "(icmp eq/ne (shl const2, A), const1)" ->
+/// (icmp eq/ne A, TrailingZeros(const1) - TrailingZeros(const2)).
+Instruction *InstCombiner::FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A,
+ ConstantInt *CI1,
+ ConstantInt *CI2) {
+ assert(I.isEquality() && "Cannot fold icmp gt/lt");
+
+ auto getConstant = [&I, this](bool IsTrue) {
+ if (I.getPredicate() == I.ICMP_NE)
+ IsTrue = !IsTrue;
+ return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), IsTrue));
+ };
+
+ auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
+ if (I.getPredicate() == I.ICMP_NE)
+ Pred = CmpInst::getInversePredicate(Pred);
+ return new ICmpInst(Pred, LHS, RHS);
+ };
+
+ APInt AP1 = CI1->getValue();
+ APInt AP2 = CI2->getValue();
+
+ // Don't bother doing any work for cases which InstSimplify handles.
+ if (AP2 == 0)
+ return nullptr;
+
+ unsigned AP2TrailingZeros = AP2.countTrailingZeros();
+
+ if (!AP1 && AP2TrailingZeros != 0)
+ return getICmp(I.ICMP_UGE, A,
+ ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
+
+ if (AP1 == AP2)
+ return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
+
+ // Get the distance between the lowest bits that are set.
+ int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
+
+ if (Shift > 0 && AP2.shl(Shift) == AP1)
+ return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
+
+ // Shifting const2 will never be equal to const1.
+ return getConstant(false);
+}
/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
///
unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits();
APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
- computeKnownBits(LHSI->getOperand(0), KnownZero, KnownOne);
+ computeKnownBits(LHSI->getOperand(0), KnownZero, KnownOne, 0, &ICI);
// If all the high bits are known, we can do this xform.
if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) {
return &ICI;
}
+ // (icmp pred (and (or (lshr X, Y), X), 1), 0) -->
+ // (icmp pred (and X, (or (shl 1, Y), 1), 0))
+ //
+ // iff pred isn't signed
+ {
+ Value *X, *Y, *LShr;
+ if (!ICI.isSigned() && RHSV == 0) {
+ if (match(LHSI->getOperand(1), m_One())) {
+ Constant *One = cast<Constant>(LHSI->getOperand(1));
+ Value *Or = LHSI->getOperand(0);
+ if (match(Or, m_Or(m_Value(LShr), m_Value(X))) &&
+ match(LShr, m_LShr(m_Specific(X), m_Value(Y)))) {
+ unsigned UsesRemoved = 0;
+ if (LHSI->hasOneUse())
+ ++UsesRemoved;
+ if (Or->hasOneUse())
+ ++UsesRemoved;
+ if (LShr->hasOneUse())
+ ++UsesRemoved;
+ Value *NewOr = nullptr;
+ // Compute X & ((1 << Y) | 1)
+ if (auto *C = dyn_cast<Constant>(Y)) {
+ if (UsesRemoved >= 1)
+ NewOr =
+ ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
+ } else {
+ if (UsesRemoved >= 3)
+ NewOr = Builder->CreateOr(Builder->CreateShl(One, Y,
+ LShr->getName(),
+ /*HasNUW=*/true),
+ One, Or->getName());
+ }
+ if (NewOr) {
+ Value *NewAnd = Builder->CreateAnd(X, NewOr, LHSI->getName());
+ ICI.setOperand(0, NewAnd);
+ return &ICI;
+ }
+ }
+ }
+ }
+ }
+
// Replace ((X & AndCst) > RHSV) with ((X & AndCst) != 0), if any
// bit set in (X & AndCst) will produce a result greater than RHSV.
if (ICI.getPredicate() == ICmpInst::ICMP_UGT) {
unsigned RHSLog2 = RHSV.logBase2();
// (1 << X) >= 2147483648 -> X >= 31 -> X == 31
- // (1 << X) > 2147483648 -> X > 31 -> false
- // (1 << X) <= 2147483648 -> X <= 31 -> true
// (1 << X) < 2147483648 -> X < 31 -> X != 31
if (RHSLog2 == TypeBits-1) {
if (Pred == ICmpInst::ICMP_UGE)
Pred = ICmpInst::ICMP_EQ;
- else if (Pred == ICmpInst::ICMP_UGT)
- return ReplaceInstUsesWith(ICI, Builder->getFalse());
- else if (Pred == ICmpInst::ICMP_ULE)
- return ReplaceInstUsesWith(ICI, Builder->getTrue());
else if (Pred == ICmpInst::ICMP_ULT)
Pred = ICmpInst::ICMP_NE;
}
if (RHSVIsPowerOf2)
return new ICmpInst(
Pred, X, ConstantInt::get(RHS->getType(), RHSV.logBase2()));
-
- return ReplaceInstUsesWith(
- ICI, Pred == ICmpInst::ICMP_EQ ? Builder->getFalse()
- : Builder->getTrue());
}
}
break;
if (DL && LHSCI->getOpcode() == Instruction::PtrToInt &&
DL->getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
Value *RHSOp = nullptr;
- if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
+ if (PtrToIntOperator *RHSC = dyn_cast<PtrToIntOperator>(ICI.getOperand(1))) {
+ Value *RHSCIOp = RHSC->getOperand(0);
+ if (RHSCIOp->getType()->getPointerAddressSpace() ==
+ LHSCIOp->getType()->getPointerAddressSpace()) {
+ RHSOp = RHSC->getOperand(0);
+ // If the pointer types don't match, insert a bitcast.
+ if (LHSCIOp->getType() != RHSOp->getType())
+ RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
+ }
+ } else if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1)))
RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
- } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
- RHSOp = RHSC->getOperand(0);
- // If the pointer types don't match, insert a bitcast.
- if (LHSCIOp->getType() != RHSOp->getType())
- RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
- }
if (RHSOp)
return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);
// sign-extended; check for that condition. For example, if CI2 is 2^31 and
// the operands of the add are 64 bits wide, we need at least 33 sign bits.
unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
- if (IC.ComputeNumSignBits(A) < NeededSignBits ||
- IC.ComputeNumSignBits(B) < NeededSignBits)
+ if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
+ IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
return nullptr;
// In order to replace the original add with a narrower
/// replacement required.
static Instruction *ProcessUMulZExtIdiom(ICmpInst &I, Value *MulVal,
Value *OtherVal, InstCombiner &IC) {
+ // Don't bother doing this transformation for pointers, don't do it for
+ // vectors.
+ if (!isa<IntegerType>(MulVal->getType()))
+ return nullptr;
+
assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
- assert(isa<IntegerType>(MulVal->getType()));
Instruction *MulInstr = cast<Instruction>(MulVal);
assert(MulInstr->getOpcode() == Instruction::Mul);
- Instruction *LHS = cast<Instruction>(MulInstr->getOperand(0)),
- *RHS = cast<Instruction>(MulInstr->getOperand(1));
+ auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
+ *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
assert(LHS->getOpcode() == Instruction::ZExt);
assert(RHS->getOpcode() == Instruction::ZExt);
Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
return GlobalSwapBenefits > 0;
}
+/// \brief Check that one use is in the same block as the definition and all
+/// other uses are in blocks dominated by a given block
+///
+/// \param DI Definition
+/// \param UI Use
+/// \param DB Block that must dominate all uses of \p DI outside
+/// the parent block
+/// \return true when \p UI is the only use of \p DI in the parent block
+/// and all other uses of \p DI are in blocks dominated by \p DB.
+///
+bool InstCombiner::dominatesAllUses(const Instruction *DI,
+ const Instruction *UI,
+ const BasicBlock *DB) const {
+ assert(DI && UI && "Instruction not defined\n");
+ // ignore incomplete definitions
+ if (!DI->getParent())
+ return false;
+ // DI and UI must be in the same block
+ if (DI->getParent() != UI->getParent())
+ return false;
+ // Protect from self-referencing blocks
+ if (DI->getParent() == DB)
+ return false;
+ // DominatorTree available?
+ if (!DT)
+ return false;
+ for (const User *U : DI->users()) {
+ auto *Usr = cast<Instruction>(U);
+ if (Usr != UI && !DT->dominates(DB, Usr->getParent()))
+ return false;
+ }
+ return true;
+}
+
+///
+/// true when the instruction sequence within a block is select-cmp-br.
+///
+static bool isChainSelectCmpBranch(const SelectInst *SI) {
+ const BasicBlock *BB = SI->getParent();
+ if (!BB)
+ return false;
+ auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
+ if (!BI || BI->getNumSuccessors() != 2)
+ return false;
+ auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
+ if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
+ return false;
+ return true;
+}
+
+///
+/// \brief True when a select result is replaced by one of its operands
+/// in select-icmp sequence. This will eventually result in the elimination
+/// of the select.
+///
+/// \param SI Select instruction
+/// \param Icmp Compare instruction
+/// \param SIOpd Operand that replaces the select
+///
+/// Notes:
+/// - The replacement is global and requires dominator information
+/// - The caller is responsible for the actual replacement
+///
+/// Example:
+///
+/// entry:
+/// %4 = select i1 %3, %C* %0, %C* null
+/// %5 = icmp eq %C* %4, null
+/// br i1 %5, label %9, label %7
+/// ...
+/// ; <label>:7 ; preds = %entry
+/// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
+/// ...
+///
+/// can be transformed to
+///
+/// %5 = icmp eq %C* %0, null
+/// %6 = select i1 %3, i1 %5, i1 true
+/// br i1 %6, label %9, label %7
+/// ...
+/// ; <label>:7 ; preds = %entry
+/// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
+///
+/// Similar when the first operand of the select is a constant or/and
+/// the compare is for not equal rather than equal.
+///
+/// NOTE: The function is only called when the select and compare constants
+/// are equal, the optimization can work only for EQ predicates. This is not a
+/// major restriction since a NE compare should be 'normalized' to an equal
+/// compare, which usually happens in the combiner and test case
+/// select-cmp-br.ll
+/// checks for it.
+bool InstCombiner::replacedSelectWithOperand(SelectInst *SI,
+ const ICmpInst *Icmp,
+ const unsigned SIOpd) {
+ assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
+ if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
+ BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
+ // The check for the unique predecessor is not the best that can be
+ // done. But it protects efficiently against cases like when SI's
+ // home block has two successors, Succ and Succ1, and Succ1 predecessor
+ // of Succ. Then SI can't be replaced by SIOpd because the use that gets
+ // replaced can be reached on either path. So the uniqueness check
+ // guarantees that the path all uses of SI (outside SI's parent) are on
+ // is disjoint from all other paths out of SI. But that information
+ // is more expensive to compute, and the trade-off here is in favor
+ // of compile-time.
+ if (Succ->getUniquePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
+ NumSel++;
+ SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
+ return true;
+ }
+ }
+ return false;
+}
+
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
bool Changed = false;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Changed = true;
}
- if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL))
+ if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// comparing -val or val with non-zero is the same as just comparing val
return Res;
}
- // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
- if (I.isEquality() && CI->isZero() &&
- match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
- // (icmp cond A B) if cond is equality
- return new ICmpInst(I.getPredicate(), A, B);
+ // The following transforms are only 'worth it' if the only user of the
+ // subtraction is the icmp.
+ if (Op0->hasOneUse()) {
+ // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
+ if (I.isEquality() && CI->isZero() &&
+ match(Op0, m_Sub(m_Value(A), m_Value(B))))
+ return new ICmpInst(I.getPredicate(), A, B);
+
+ // (icmp sgt (sub nsw A B), -1) -> (icmp sge A, B)
+ if (I.getPredicate() == ICmpInst::ICMP_SGT && CI->isAllOnesValue() &&
+ match(Op0, m_NSWSub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SGE, A, B);
+
+ // (icmp sgt (sub nsw A B), 0) -> (icmp sgt A, B)
+ if (I.getPredicate() == ICmpInst::ICMP_SGT && CI->isZero() &&
+ match(Op0, m_NSWSub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SGT, A, B);
+
+ // (icmp slt (sub nsw A B), 0) -> (icmp slt A, B)
+ if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isZero() &&
+ match(Op0, m_NSWSub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SLT, A, B);
+
+ // (icmp slt (sub nsw A B), 1) -> (icmp sle A, B)
+ if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isOne() &&
+ match(Op0, m_NSWSub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SLE, A, B);
}
// If we have an icmp le or icmp ge instruction, turn it into the
Builder->getInt(CI->getValue()-1));
}
+ if (I.isEquality()) {
+ ConstantInt *CI2;
+ if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) ||
+ match(Op0, m_LShr(m_ConstantInt(CI2), m_Value(A)))) {
+ // (icmp eq/ne (ashr/lshr const2, A), const1)
+ if (Instruction *Inst = FoldICmpCstShrCst(I, Op0, A, CI, CI2))
+ return Inst;
+ }
+ if (match(Op0, m_Shl(m_ConstantInt(CI2), m_Value(A)))) {
+ // (icmp eq/ne (shl const2, A), const1)
+ if (Instruction *Inst = FoldICmpCstShlCst(I, Op0, A, CI, CI2))
+ return Inst;
+ }
+ }
+
// If this comparison is a normal comparison, it demands all
// bits, if it is a sign bit comparison, it only demands the sign bit.
bool UnusedBit;
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
- if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) == 0" into "x != 3".
+ // or turn "((1 << x)&7) == 0" into "x > 2".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
- unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
- return new ICmpInst(ICmpInst::ICMP_NE, X,
- ConstantInt::get(X->getType(), CmpVal));
+ APInt ValToCheck = Op0KnownZeroInverted;
+ if (ValToCheck.isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ } else if ((++ValToCheck).isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros() - 1;
+ return new ICmpInst(ICmpInst::ICMP_UGT, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
- if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) != 0" into "x == 3".
+ // or turn "((1 << x)&7) != 0" into "x < 3".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
- unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
- return new ICmpInst(ICmpInst::ICMP_EQ, X,
- ConstantInt::get(X->getType(), CmpVal));
+ APInt ValToCheck = Op0KnownZeroInverted;
+ if (ValToCheck.isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ } else if ((++ValToCheck).isPowerOf2()) {
+ unsigned CmpVal = ValToCheck.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_ULT, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
// comparison into the select arms, which will cause one to be
// constant folded and the select turned into a bitwise or.
Value *Op1 = nullptr, *Op2 = nullptr;
- if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1)))
+ ConstantInt *CI = 0;
+ if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
- if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2)))
+ CI = dyn_cast<ConstantInt>(Op1);
+ }
+ if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
+ CI = dyn_cast<ConstantInt>(Op2);
+ }
// We only want to perform this transformation if it will not lead to
// additional code. This is true if either both sides of the select
// fold to a constant (in which case the icmp is replaced with a select
// which will usually simplify) or this is the only user of the
// select (in which case we are trading a select+icmp for a simpler
- // select+icmp).
- if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) {
+ // select+icmp) or all uses of the select can be replaced based on
+ // dominance information ("Global cases").
+ bool Transform = false;
+ if (Op1 && Op2)
+ Transform = true;
+ else if (Op1 || Op2) {
+ // Local case
+ if (LHSI->hasOneUse())
+ Transform = true;
+ // Global cases
+ else if (CI && !CI->isZero())
+ // When Op1 is constant try replacing select with second operand.
+ // Otherwise Op2 is constant and try replacing select with first
+ // operand.
+ Transform = replacedSelectWithOperand(cast<SelectInst>(LHSI), &I,
+ Op1 ? 2 : 1);
+ }
+ if (Transform) {
if (!Op1)
Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1),
RHSC, I.getName());
if (BO1 && BO1->getOpcode() == Instruction::Add)
C = BO1->getOperand(0), D = BO1->getOperand(1);
+ // icmp (X+cst) < 0 --> X < -cst
+ if (NoOp0WrapProblem && ICmpInst::isSigned(Pred) && match(Op1, m_Zero()))
+ if (ConstantInt *RHSC = dyn_cast_or_null<ConstantInt>(B))
+ if (!RHSC->isMinValue(/*isSigned=*/true))
+ return new ICmpInst(Pred, A, ConstantExpr::getNeg(RHSC));
+
// icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
return new ICmpInst(Pred, A == Op1 ? B : A,
// and (A & ~B) != 0 --> (A & B) == 0
// if A is a power of 2.
if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
- match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(A) && I.isEquality())
+ match(Op1, m_Zero()) &&
+ isKnownToBeAPowerOfTwo(A, false, 0, AC, &I, DT) && I.isEquality())
return new ICmpInst(I.getInversePredicate(),
Builder->CreateAnd(A, B),
Op1);
}
}
+ // The 'cmpxchg' instruction returns an aggregate containing the old value and
+ // an i1 which indicates whether or not we successfully did the swap.
+ //
+ // Replace comparisons between the old value and the expected value with the
+ // indicator that 'cmpxchg' returns.
+ //
+ // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
+ // spuriously fail. In those cases, the old value may equal the expected
+ // value but it is possible for the swap to not occur.
+ if (I.getPredicate() == ICmpInst::ICMP_EQ)
+ if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
+ if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
+ if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
+ !ACXI->isWeak())
+ return ExtractValueInst::Create(ACXI, 1);
+
{
Value *X; ConstantInt *Cst;
// icmp X+Cst, X
}
/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
-///
Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
Instruction *LHSI,
Constant *RHSC) {
int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
if (MantissaWidth == -1) return nullptr; // Unknown.
+ IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
+
// Check to see that the input is converted from an integer type that is small
// enough that preserves all bits. TODO: check here for "known" sign bits.
// This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
- unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits();
+ unsigned InputSize = IntTy->getScalarSizeInBits();
// If this is a uitofp instruction, we need an extra bit to hold the sign.
bool LHSUnsigned = isa<UIToFPInst>(LHSI);
if (LHSUnsigned)
++InputSize;
+ if (I.isEquality()) {
+ FCmpInst::Predicate P = I.getPredicate();
+ bool IsExact = false;
+ APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
+ RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
+
+ // If the floating point constant isn't an integer value, we know if we will
+ // ever compare equal / not equal to it.
+ if (!IsExact) {
+ // TODO: Can never be -0.0 and other non-representable values
+ APFloat RHSRoundInt(RHS);
+ RHSRoundInt.roundToIntegral(APFloat::rmNearestTiesToEven);
+ if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
+ if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
+ return ReplaceInstUsesWith(I, Builder->getFalse());
+
+ assert(P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE);
+ return ReplaceInstUsesWith(I, Builder->getTrue());
+ }
+ }
+
+ // TODO: If the constant is exactly representable, is it always OK to do
+ // equality compares as integer?
+ }
+
+ // Comparisons with zero are a special case where we know we won't lose
+ // information.
+ bool IsCmpZero = RHS.isPosZero();
+
// If the conversion would lose info, don't hack on this.
- if ((int)InputSize > MantissaWidth)
+ if ((int)InputSize > MantissaWidth && !IsCmpZero)
return nullptr;
// Otherwise, we can potentially simplify the comparison. We know that it
return ReplaceInstUsesWith(I, Builder->getFalse());
}
- IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
-
// Now we know that the APFloat is a normal number, zero or inf.
// See if the FP constant is too large for the integer. For example,
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
- if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL))
+ if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// Simplify 'fcmp pred X, X'
}
break;
case Instruction::Call: {
+ if (!RHSC->isNullValue())
+ break;
+
CallInst *CI = cast<CallInst>(LHSI);
- LibFunc::Func Func;
+ const Function *F = CI->getCalledFunction();
+ if (!F)
+ break;
+
// Various optimization for fabs compared with zero.
- if (RHSC->isNullValue() && CI->getCalledFunction() &&
- TLI->getLibFunc(CI->getCalledFunction()->getName(), Func) &&
- TLI->has(Func)) {
- if (Func == LibFunc::fabs || Func == LibFunc::fabsf ||
- Func == LibFunc::fabsl) {
- switch (I.getPredicate()) {
- default: break;
+ LibFunc::Func Func;
+ if (F->getIntrinsicID() == Intrinsic::fabs ||
+ (TLI->getLibFunc(F->getName(), Func) && TLI->has(Func) &&
+ (Func == LibFunc::fabs || Func == LibFunc::fabsf ||
+ Func == LibFunc::fabsl))) {
+ switch (I.getPredicate()) {
+ default:
+ break;
// fabs(x) < 0 --> false
- case FCmpInst::FCMP_OLT:
- return ReplaceInstUsesWith(I, Builder->getFalse());
+ case FCmpInst::FCMP_OLT:
+ return ReplaceInstUsesWith(I, Builder->getFalse());
// fabs(x) > 0 --> x != 0
- case FCmpInst::FCMP_OGT:
- return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0),
- RHSC);
+ case FCmpInst::FCMP_OGT:
+ return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC);
// fabs(x) <= 0 --> x == 0
- case FCmpInst::FCMP_OLE:
- return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0),
- RHSC);
+ case FCmpInst::FCMP_OLE:
+ return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC);
// fabs(x) >= 0 --> !isnan(x)
- case FCmpInst::FCMP_OGE:
- return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0),
- RHSC);
+ case FCmpInst::FCMP_OGE:
+ return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC);
// fabs(x) == 0 --> x == 0
// fabs(x) != 0 --> x != 0
- case FCmpInst::FCMP_OEQ:
- case FCmpInst::FCMP_UEQ:
- case FCmpInst::FCMP_ONE:
- case FCmpInst::FCMP_UNE:
- return new FCmpInst(I.getPredicate(), CI->getArgOperand(0),
- RHSC);
- }
+ case FCmpInst::FCMP_OEQ:
+ case FCmpInst::FCMP_UEQ:
+ case FCmpInst::FCMP_ONE:
+ case FCmpInst::FCMP_UNE:
+ return new FCmpInst(I.getPredicate(), CI->getArgOperand(0), RHSC);
}
}
}