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-rw-r--r--lib/Transforms/InstCombine/InstCombineSelect.cpp261
1 files changed, 207 insertions, 54 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 079ae34..dd0e65f 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -11,7 +11,7 @@
//
//===----------------------------------------------------------------------===//
-#include "InstCombine.h"
+#include "InstCombineInternal.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/PatternMatch.h"
@@ -314,8 +314,7 @@ Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
const DataLayout *TD,
const TargetLibraryInfo *TLI,
- DominatorTree *DT,
- AssumptionTracker *AT) {
+ DominatorTree *DT, AssumptionCache *AC) {
// Trivial replacement.
if (V == Op)
return RepOp;
@@ -336,10 +335,10 @@ static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
if (CmpInst *C = dyn_cast<CmpInst>(I)) {
if (C->getOperand(0) == Op)
return SimplifyCmpInst(C->getPredicate(), RepOp, C->getOperand(1), TD,
- TLI, DT, AT);
+ TLI, DT, AC);
if (C->getOperand(1) == Op)
return SimplifyCmpInst(C->getPredicate(), C->getOperand(0), RepOp, TD,
- TLI, DT, AT);
+ TLI, DT, AC);
}
// TODO: We could hand off more cases to instsimplify here.
@@ -389,15 +388,7 @@ static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
/// 1. The icmp predicate is inverted
/// 2. The select operands are reversed
/// 3. The magnitude of C2 and C1 are flipped
-///
-/// This also tries to turn
-/// --- Single bit tests:
-/// if ((x & C) == 0) x |= C to x |= C
-/// if ((x & C) != 0) x ^= C to x &= ~C
-/// if ((x & C) == 0) x ^= C to x |= C
-/// if ((x & C) != 0) x &= ~C to x &= ~C
-/// if ((x & C) == 0) x &= ~C to nothing
-static Value *foldSelectICmpAndOr(SelectInst &SI, Value *TrueVal,
+static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
Value *FalseVal,
InstCombiner::BuilderTy *Builder) {
const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
@@ -416,25 +407,6 @@ static Value *foldSelectICmpAndOr(SelectInst &SI, Value *TrueVal,
return nullptr;
const APInt *C2;
- if (match(TrueVal, m_Specific(X))) {
- // if ((X & C) != 0) X ^= C becomes X &= ~C
- if (match(FalseVal, m_Xor(m_Specific(X), m_APInt(C2))) && C1 == C2)
- return Builder->CreateAnd(X, ~(*C1));
- // if ((X & C) != 0) X &= ~C becomes X &= ~C
- if (match(FalseVal, m_And(m_Specific(X), m_APInt(C2))) && *C1 == ~(*C2))
- return FalseVal;
- } else if (match(FalseVal, m_Specific(X))) {
- // if ((X & C) == 0) X ^= C becomes X |= C
- if (match(TrueVal, m_Xor(m_Specific(X), m_APInt(C2))) && C1 == C2)
- return Builder->CreateOr(X, *C1);
- // if ((X & C) == 0) X &= ~C becomes nothing
- if (match(TrueVal, m_And(m_Specific(X), m_APInt(C2))) && *C1 == ~(*C2))
- return X;
- // if ((X & C) == 0) X |= C becomes X |= C
- if (match(TrueVal, m_Or(m_Specific(X), m_APInt(C2))) && C1 == C2)
- return TrueVal;
- }
-
bool OrOnTrueVal = false;
bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
if (!OrOnFalseVal)
@@ -465,6 +437,62 @@ static Value *foldSelectICmpAndOr(SelectInst &SI, Value *TrueVal,
return Builder->CreateOr(V, Y);
}
+/// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single
+/// call to cttz/ctlz with flag 'is_zero_undef' cleared.
+///
+/// For example, we can fold the following code sequence:
+/// \code
+/// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
+/// %1 = icmp ne i32 %x, 0
+/// %2 = select i1 %1, i32 %0, i32 32
+/// \code
+///
+/// into:
+/// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
+static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
+ InstCombiner::BuilderTy *Builder) {
+ ICmpInst::Predicate Pred = ICI->getPredicate();
+ Value *CmpLHS = ICI->getOperand(0);
+ Value *CmpRHS = ICI->getOperand(1);
+
+ // Check if the condition value compares a value for equality against zero.
+ if (!ICI->isEquality() || !match(CmpRHS, m_Zero()))
+ return nullptr;
+
+ Value *Count = FalseVal;
+ Value *ValueOnZero = TrueVal;
+ if (Pred == ICmpInst::ICMP_NE)
+ std::swap(Count, ValueOnZero);
+
+ // Skip zero extend/truncate.
+ Value *V = nullptr;
+ if (match(Count, m_ZExt(m_Value(V))) ||
+ match(Count, m_Trunc(m_Value(V))))
+ Count = V;
+
+ // Check if the value propagated on zero is a constant number equal to the
+ // sizeof in bits of 'Count'.
+ unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits();
+ if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits)))
+ return nullptr;
+
+ // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the
+ // input to the cttz/ctlz is used as LHS for the compare instruction.
+ if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) ||
+ match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) {
+ IntrinsicInst *II = cast<IntrinsicInst>(Count);
+ IRBuilder<> Builder(II);
+ // Explicitly clear the 'undef_on_zero' flag.
+ IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone());
+ Type *Ty = NewI->getArgOperand(1)->getType();
+ NewI->setArgOperand(1, Constant::getNullValue(Ty));
+ Builder.Insert(NewI);
+ return Builder.CreateZExtOrTrunc(NewI, ValueOnZero->getType());
+ }
+
+ return nullptr;
+}
+
/// visitSelectInstWithICmp - Visit a SelectInst that has an
/// ICmpInst as its first operand.
///
@@ -607,26 +635,26 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
// arms of the select. See if substituting this value into the arm and
// simplifying the result yields the same value as the other arm.
if (Pred == ICmpInst::ICMP_EQ) {
- if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI,
- DT, AT) == TrueVal ||
- SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI,
- DT, AT) == TrueVal)
+ if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
+ TrueVal ||
+ SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
+ TrueVal)
return ReplaceInstUsesWith(SI, FalseVal);
- if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI,
- DT, AT) == FalseVal ||
- SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI,
- DT, AT) == FalseVal)
+ if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
+ FalseVal ||
+ SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
+ FalseVal)
return ReplaceInstUsesWith(SI, FalseVal);
} else if (Pred == ICmpInst::ICMP_NE) {
- if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI,
- DT, AT) == FalseVal ||
- SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI,
- DT, AT) == FalseVal)
+ if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
+ FalseVal ||
+ SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
+ FalseVal)
return ReplaceInstUsesWith(SI, TrueVal);
- if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI,
- DT, AT) == TrueVal ||
- SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI,
- DT, AT) == TrueVal)
+ if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
+ TrueVal ||
+ SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
+ TrueVal)
return ReplaceInstUsesWith(SI, TrueVal);
}
@@ -644,9 +672,58 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
}
}
+ if (unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits()) {
+ APInt MinSignedValue = APInt::getSignBit(BitWidth);
+ Value *X;
+ const APInt *Y, *C;
+ bool TrueWhenUnset;
+ bool IsBitTest = false;
+ if (ICmpInst::isEquality(Pred) &&
+ match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
+ match(CmpRHS, m_Zero())) {
+ IsBitTest = true;
+ TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
+ } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
+ X = CmpLHS;
+ Y = &MinSignedValue;
+ IsBitTest = true;
+ TrueWhenUnset = false;
+ } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
+ X = CmpLHS;
+ Y = &MinSignedValue;
+ IsBitTest = true;
+ TrueWhenUnset = true;
+ }
+ if (IsBitTest) {
+ Value *V = nullptr;
+ // (X & Y) == 0 ? X : X ^ Y --> X & ~Y
+ if (TrueWhenUnset && TrueVal == X &&
+ match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+ V = Builder->CreateAnd(X, ~(*Y));
+ // (X & Y) != 0 ? X ^ Y : X --> X & ~Y
+ else if (!TrueWhenUnset && FalseVal == X &&
+ match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+ V = Builder->CreateAnd(X, ~(*Y));
+ // (X & Y) == 0 ? X ^ Y : X --> X | Y
+ else if (TrueWhenUnset && FalseVal == X &&
+ match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+ V = Builder->CreateOr(X, *Y);
+ // (X & Y) != 0 ? X : X ^ Y --> X | Y
+ else if (!TrueWhenUnset && TrueVal == X &&
+ match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
+ V = Builder->CreateOr(X, *Y);
+
+ if (V)
+ return ReplaceInstUsesWith(SI, V);
+ }
+ }
+
if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
return ReplaceInstUsesWith(SI, V);
+ if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder))
+ return ReplaceInstUsesWith(SI, V);
+
return Changed ? &SI : nullptr;
}
@@ -835,8 +912,8 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *TrueVal = SI.getTrueValue();
Value *FalseVal = SI.getFalseValue();
- if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI,
- DT, AT))
+ if (Value *V =
+ SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC))
return ReplaceInstUsesWith(SI, V);
if (SI.getType()->isIntegerTy(1)) {
@@ -928,8 +1005,22 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, TrueVal);
}
- // NOTE: if we wanted to, this is where to detect MIN/MAX
+ // Canonicalize to use ordered comparisons by swapping the select
+ // operands.
+ //
+ // e.g.
+ // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
+ if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
+ FCmpInst::Predicate InvPred = FCI->getInversePredicate();
+ Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
+ FCI->getName() + ".inv");
+
+ return SelectInst::Create(NewCond, FalseVal, TrueVal,
+ SI.getName() + ".p");
+ }
+
+ // NOTE: if we wanted to, this is where to detect MIN/MAX
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
// Transform (X == Y) ? Y : X -> X
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
@@ -955,6 +1046,21 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
!CFPf->getValueAPF().isZero()))
return ReplaceInstUsesWith(SI, TrueVal);
}
+
+ // Canonicalize to use ordered comparisons by swapping the select
+ // operands.
+ //
+ // e.g.
+ // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
+ if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
+ FCmpInst::Predicate InvPred = FCI->getInversePredicate();
+ Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
+ FCI->getName() + ".inv");
+
+ return SelectInst::Create(NewCond, FalseVal, TrueVal,
+ SI.getName() + ".p");
+ }
+
// NOTE: if we wanted to, this is where to detect MIN/MAX
}
// NOTE: if we wanted to, this is where to detect ABS
@@ -1039,12 +1145,14 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
return FoldI;
+ Value *LHS, *RHS, *LHS2, *RHS2;
+ SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS);
+
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
- Value *LHS, *RHS, *LHS2, *RHS2;
- if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
+ if (SPF) {
if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
SI, SPF, RHS))
@@ -1055,6 +1163,33 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return R;
}
+ // MAX(~a, ~b) -> ~MIN(a, b)
+ if (SPF == SPF_SMAX || SPF == SPF_UMAX) {
+ if (IsFreeToInvert(LHS, LHS->hasNUses(2)) &&
+ IsFreeToInvert(RHS, RHS->hasNUses(2))) {
+
+ // This transform adds a xor operation and that extra cost needs to be
+ // justified. We look for simplifications that will result from
+ // applying this rule:
+
+ bool Profitable =
+ (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) ||
+ (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) ||
+ (SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value())));
+
+ if (Profitable) {
+ Value *NewLHS = Builder->CreateNot(LHS);
+ Value *NewRHS = Builder->CreateNot(RHS);
+ Value *NewCmp = SPF == SPF_SMAX
+ ? Builder->CreateICmpSLT(NewLHS, NewRHS)
+ : Builder->CreateICmpULT(NewLHS, NewRHS);
+ Value *NewSI =
+ Builder->CreateNot(Builder->CreateSelect(NewCmp, NewLHS, NewRHS));
+ return ReplaceInstUsesWith(SI, NewSI);
+ }
+ }
+ }
+
// TODO.
// ABS(-X) -> ABS(X)
}
@@ -1068,20 +1203,38 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return NV;
if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
+ // select(C, select(C, a, b), c) -> select(C, a, c)
if (TrueSI->getCondition() == CondVal) {
if (SI.getTrueValue() == TrueSI->getTrueValue())
return nullptr;
SI.setOperand(1, TrueSI->getTrueValue());
return &SI;
}
+ // select(C0, select(C1, a, b), b) -> select(C0&C1, a, b)
+ // We choose this as normal form to enable folding on the And and shortening
+ // paths for the values (this helps GetUnderlyingObjects() for example).
+ if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) {
+ Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition());
+ SI.setOperand(0, And);
+ SI.setOperand(1, TrueSI->getTrueValue());
+ return &SI;
+ }
}
if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
+ // select(C, a, select(C, b, c)) -> select(C, a, c)
if (FalseSI->getCondition() == CondVal) {
if (SI.getFalseValue() == FalseSI->getFalseValue())
return nullptr;
SI.setOperand(2, FalseSI->getFalseValue());
return &SI;
}
+ // select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b)
+ if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) {
+ Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition());
+ SI.setOperand(0, Or);
+ SI.setOperand(2, FalseSI->getFalseValue());
+ return &SI;
+ }
}
if (BinaryOperator::isNot(CondVal)) {
generated by cgit v1.1 at 2024-12-22 11:01:02 +0000