Implement some basic simplifications involving min/max, for example
max(a,b) >= a -> true. According to my super-optimizer, these are by far the most common simplifications (of the -instsimplify kind) that occur in the testsuite and aren't caught by -std-compile-opts. llvm-svn: 130780
This commit is contained in:
Duncan Sands
parent
e6ce2053e7
commit
0a9c1246d7
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@ -694,6 +694,99 @@ inline brc_match<Cond_t> m_Br(const Cond_t &C, BasicBlock *&T, BasicBlock *&F) {
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return brc_match<Cond_t>(C, T, F);
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}
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//===----------------------------------------------------------------------===//
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// Matchers for max/min idioms, eg: "select (sgt x, y), x, y" -> smax(x,y).
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//
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template<typename LHS_t, typename RHS_t, typename Pred_t>
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struct MaxMin_match {
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LHS_t L;
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RHS_t R;
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MaxMin_match(const LHS_t &LHS, const RHS_t &RHS)
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: L(LHS), R(RHS) {}
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template<typename OpTy>
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bool match(OpTy *V) {
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// Look for "(x pred y) ? x : y" or "(x pred y) ? y : x".
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SelectInst *SI = dyn_cast<SelectInst>(V);
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if (!SI)
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return false;
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ICmpInst *Cmp = dyn_cast<ICmpInst>(SI->getCondition());
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if (!Cmp)
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return false;
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// At this point we have a select conditioned on a comparison. Check that
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// it is the values returned by the select that are being compared.
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Value *TrueVal = SI->getTrueValue();
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Value *FalseVal = SI->getFalseValue();
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Value *LHS = Cmp->getOperand(0);
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Value *RHS = Cmp->getOperand(1);
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if ((TrueVal != LHS || FalseVal != RHS) &&
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(TrueVal != RHS || FalseVal != LHS))
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return false;
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ICmpInst::Predicate Pred = LHS == TrueVal ?
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Cmp->getPredicate() : Cmp->getSwappedPredicate();
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// Does "(x pred y) ? x : y" represent the desired max/min operation?
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if (!Pred_t::match(Pred))
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return false;
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// It does! Bind the operands.
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return L.match(LHS) && R.match(RHS);
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}
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};
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/// smax_pred_ty - Helper class for identifying signed max predicates.
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struct smax_pred_ty {
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static bool match(ICmpInst::Predicate Pred) {
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return Pred == CmpInst::ICMP_SGT || Pred == CmpInst::ICMP_SGE;
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}
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};
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/// smin_pred_ty - Helper class for identifying signed min predicates.
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struct smin_pred_ty {
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static bool match(ICmpInst::Predicate Pred) {
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return Pred == CmpInst::ICMP_SLT || Pred == CmpInst::ICMP_SLE;
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}
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};
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/// umax_pred_ty - Helper class for identifying unsigned max predicates.
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struct umax_pred_ty {
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static bool match(ICmpInst::Predicate Pred) {
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return Pred == CmpInst::ICMP_UGT || Pred == CmpInst::ICMP_UGE;
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}
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};
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/// umin_pred_ty - Helper class for identifying unsigned min predicates.
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struct umin_pred_ty {
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static bool match(ICmpInst::Predicate Pred) {
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return Pred == CmpInst::ICMP_ULT || Pred == CmpInst::ICMP_ULE;
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}
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};
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template<typename LHS, typename RHS>
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inline MaxMin_match<LHS, RHS, smax_pred_ty>
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m_SMax(const LHS &L, const RHS &R) {
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return MaxMin_match<LHS, RHS, smax_pred_ty>(L, R);
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}
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template<typename LHS, typename RHS>
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inline MaxMin_match<LHS, RHS, smin_pred_ty>
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m_SMin(const LHS &L, const RHS &R) {
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return MaxMin_match<LHS, RHS, smin_pred_ty>(L, R);
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}
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template<typename LHS, typename RHS>
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inline MaxMin_match<LHS, RHS, umax_pred_ty>
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m_UMax(const LHS &L, const RHS &R) {
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return MaxMin_match<LHS, RHS, umax_pred_ty>(L, R);
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}
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template<typename LHS, typename RHS>
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inline MaxMin_match<LHS, RHS, umin_pred_ty>
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m_UMin(const LHS &L, const RHS &R) {
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return MaxMin_match<LHS, RHS, umin_pred_ty>(L, R);
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}
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} // end namespace PatternMatch
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} // end namespace llvm
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@ -1868,6 +1868,124 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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}
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}
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// Simplify comparisons involving max/min.
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Value *A, *B;
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CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE;
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CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B".
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// Signed max/min.
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if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
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if (A != RHS) std::swap(A, B); // smax(A, B) pred A.
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EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B".
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// We analyze this as smax(A, B) pred A.
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P = Pred;
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} else if (match(RHS, m_SMax(m_Value(A), m_Value(B))) &&
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(A == LHS || B == LHS)) {
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if (A != LHS) std::swap(A, B); // A pred smax(A, B).
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EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B".
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// We analyze this as smax(A, B) swapped-pred A.
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P = CmpInst::getSwappedPredicate(Pred);
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} else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) &&
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(A == RHS || B == RHS)) {
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if (A != RHS) std::swap(A, B); // smin(A, B) pred A.
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EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B".
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// We analyze this as smax(-A, -B) swapped-pred -A.
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// Note that we do not need to actually form -A or -B thanks to EqP.
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P = CmpInst::getSwappedPredicate(Pred);
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} else if (match(RHS, m_SMin(m_Value(A), m_Value(B))) &&
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(A == LHS || B == LHS)) {
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if (A != LHS) std::swap(A, B); // A pred smin(A, B).
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EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B".
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// We analyze this as smax(-A, -B) pred -A.
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// Note that we do not need to actually form -A or -B thanks to EqP.
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P = Pred;
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}
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if (P != CmpInst::BAD_ICMP_PREDICATE) {
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// Cases correspond to "max(A, B) p A".
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switch (P) {
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default:
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break;
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case CmpInst::ICMP_EQ:
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case CmpInst::ICMP_SLE:
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// Equivalent to "A EqP B".
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if (MaxRecurse)
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if (Value *V = SimplifyICmpInst(EqP, A, B, TD, DT, MaxRecurse-1))
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return V;
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break;
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case CmpInst::ICMP_NE:
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case CmpInst::ICMP_SGT:
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// Equivalent to "A inverse-EqP B".
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if (MaxRecurse)
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if (Value *V = SimplifyICmpInst(CmpInst::getInversePredicate(EqP), A, B,
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TD, DT, MaxRecurse-1))
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return V;
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break;
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case CmpInst::ICMP_SGE:
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// Always true.
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return Constant::getAllOnesValue(ITy);
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case CmpInst::ICMP_SLT:
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// Always false.
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return Constant::getNullValue(ITy);
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}
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}
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// Unsigned max/min.
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P = CmpInst::BAD_ICMP_PREDICATE;
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if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
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if (A != RHS) std::swap(A, B); // umax(A, B) pred A.
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EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B".
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// We analyze this as umax(A, B) pred A.
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P = Pred;
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} else if (match(RHS, m_UMax(m_Value(A), m_Value(B))) &&
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(A == LHS || B == LHS)) {
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if (A != LHS) std::swap(A, B); // A pred umax(A, B).
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EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B".
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// We analyze this as umax(A, B) swapped-pred A.
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P = CmpInst::getSwappedPredicate(Pred);
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} else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) &&
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(A == RHS || B == RHS)) {
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if (A != RHS) std::swap(A, B); // umin(A, B) pred A.
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EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B".
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// We analyze this as umax(-A, -B) swapped-pred -A.
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// Note that we do not need to actually form -A or -B thanks to EqP.
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P = CmpInst::getSwappedPredicate(Pred);
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} else if (match(RHS, m_UMin(m_Value(A), m_Value(B))) &&
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(A == LHS || B == LHS)) {
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if (A != LHS) std::swap(A, B); // A pred umin(A, B).
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EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B".
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// We analyze this as umax(-A, -B) pred -A.
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// Note that we do not need to actually form -A or -B thanks to EqP.
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P = Pred;
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}
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if (P != CmpInst::BAD_ICMP_PREDICATE) {
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// Cases correspond to "max(A, B) p A".
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switch (P) {
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default:
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break;
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case CmpInst::ICMP_EQ:
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case CmpInst::ICMP_ULE:
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// Equivalent to "A EqP B".
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if (MaxRecurse)
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if (Value *V = SimplifyICmpInst(EqP, A, B, TD, DT, MaxRecurse-1))
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return V;
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break;
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case CmpInst::ICMP_NE:
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case CmpInst::ICMP_UGT:
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// Equivalent to "A inverse-EqP B".
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if (MaxRecurse)
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if (Value *V = SimplifyICmpInst(CmpInst::getInversePredicate(EqP), A, B,
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TD, DT, MaxRecurse-1))
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return V;
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break;
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case CmpInst::ICMP_UGE:
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// Always true.
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return Constant::getAllOnesValue(ITy);
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case CmpInst::ICMP_ULT:
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// Always false.
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return Constant::getNullValue(ITy);
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}
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}
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// If the comparison is with the result of a select instruction, check whether
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// comparing with either branch of the select always yields the same value.
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if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
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@ -0,0 +1,145 @@
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; RUN: opt < %s -instsimplify -S | FileCheck %s
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define i1 @max1(i32 %x, i32 %y) {
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; CHECK: @max1
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%c = icmp sgt i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp slt i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @max2(i32 %x, i32 %y) {
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; CHECK: @max2
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%c = icmp sge i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp sge i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @max3(i32 %x, i32 %y) {
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; CHECK: @max3
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%c = icmp ugt i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp ult i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @max4(i32 %x, i32 %y) {
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; CHECK: @max4
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%c = icmp uge i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp uge i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @max5(i32 %x, i32 %y) {
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; CHECK: @max5
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%c = icmp sgt i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp sgt i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @max6(i32 %x, i32 %y) {
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; CHECK: @max6
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%c = icmp sge i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp sle i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @max7(i32 %x, i32 %y) {
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; CHECK: @max7
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%c = icmp ugt i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp ugt i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @max8(i32 %x, i32 %y) {
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; CHECK: @max8
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%c = icmp uge i32 %x, %y
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%m = select i1 %c, i32 %x, i32 %y
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%r = icmp ule i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @min1(i32 %x, i32 %y) {
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; CHECK: @min1
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%c = icmp sgt i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp sgt i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @min2(i32 %x, i32 %y) {
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; CHECK: @min2
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%c = icmp sge i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp sle i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @min3(i32 %x, i32 %y) {
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; CHECK: @min3
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%c = icmp ugt i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp ugt i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @min4(i32 %x, i32 %y) {
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; CHECK: @min4
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%c = icmp uge i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp ule i32 %m, %x
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @min5(i32 %x, i32 %y) {
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; CHECK: @min5
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%c = icmp sgt i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp slt i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @min6(i32 %x, i32 %y) {
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; CHECK: @min6
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%c = icmp sge i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp sge i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 true
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}
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define i1 @min7(i32 %x, i32 %y) {
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; CHECK: @min7
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%c = icmp ugt i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp ult i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 false
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}
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define i1 @min8(i32 %x, i32 %y) {
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; CHECK: @min8
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%c = icmp uge i32 %x, %y
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%m = select i1 %c, i32 %y, i32 %x
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%r = icmp uge i32 %x, %m
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ret i1 %r
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; CHECK: ret i1 true
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}
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