[llvm] r266939 - Add optimization for 'icmp slt (or A, B), A' and some related idioms based on knowledge of the sign bit for A and B.
Nick Lewycky via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 20 17:53:15 PDT 2016
Author: nicholas
Date: Wed Apr 20 19:53:14 2016
New Revision: 266939
URL: http://llvm.org/viewvc/llvm-project?rev=266939&view=rev
Log:
Add optimization for 'icmp slt (or A, B), A' and some related idioms based on knowledge of the sign bit for A and B.
No matter what value you OR in to A, the result of (or A, B) is going to be UGE A. When A and B are positive, it's SGE too. If A is negative, OR'ing a value into it can't make it positive, but can increase its value closer to -1, therefore (or A, B) is SGE A. Working through all possible combinations produces this truth table:
```
A is
+, -, +/-
F F F + B is
T F ? -
? F ? +/-
```
The related optimizations are flipping the 'slt' for 'sge' which always NOTs the result (if the result is known), and swapping the LHS and RHS while swapping the comparison predicate.
There are more idioms left to implement (aren't there always!) but I've stopped here because any more would risk becoming unreasonable for reviewers.
Modified:
llvm/trunk/include/llvm/Analysis/ValueTracking.h
llvm/trunk/include/llvm/IR/PatternMatch.h
llvm/trunk/lib/Analysis/InstructionSimplify.cpp
llvm/trunk/lib/Analysis/ValueTracking.cpp
llvm/trunk/test/Transforms/InstSimplify/compare.ll
Modified: llvm/trunk/include/llvm/Analysis/ValueTracking.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ValueTracking.h?rev=266939&r1=266938&r2=266939&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/ValueTracking.h (original)
+++ llvm/trunk/include/llvm/Analysis/ValueTracking.h Wed Apr 20 19:53:14 2016
@@ -105,6 +105,13 @@ template <typename T> class ArrayRef;
const Instruction *CxtI = nullptr,
const DominatorTree *DT = nullptr);
+ /// Returns true if the given value is known be negative (i.e. non-positive
+ /// and non-zero).
+ bool isKnownNegative(Value *V, const DataLayout &DL, unsigned Depth = 0,
+ AssumptionCache *AC = nullptr,
+ const Instruction *CxtI = nullptr,
+ const DominatorTree *DT = nullptr);
+
/// isKnownNonEqual - Return true if the given values are known to be
/// non-equal when defined. Supports scalar integer types only.
bool isKnownNonEqual(Value *V1, Value *V2, const DataLayout &DL,
Modified: llvm/trunk/include/llvm/IR/PatternMatch.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/PatternMatch.h?rev=266939&r1=266938&r2=266939&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/PatternMatch.h (original)
+++ llvm/trunk/include/llvm/IR/PatternMatch.h Wed Apr 20 19:53:14 2016
@@ -1312,6 +1312,43 @@ template <typename Val_t> inline Signum_
return Signum_match<Val_t>(V);
}
+//===----------------------------------------------------------------------===//
+// Matchers for two-operands operators with the operators in either order
+//
+
+/// \brief Matches an ICmp with a predicate over LHS and RHS in either order.
+/// Does not swap the predicate.
+template<typename LHS, typename RHS>
+inline match_combine_or<CmpClass_match<LHS, RHS, ICmpInst, ICmpInst::Predicate>,
+ CmpClass_match<RHS, LHS, ICmpInst, ICmpInst::Predicate>>
+m_c_ICmp(ICmpInst::Predicate &Pred, const LHS &L, const RHS &R) {
+ return m_CombineOr(m_ICmp(Pred, L, R), m_ICmp(Pred, R, L));
+}
+
+/// \brief Matches an And with LHS and RHS in either order.
+template<typename LHS, typename RHS>
+inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::And>,
+ BinaryOp_match<RHS, LHS, Instruction::And>>
+m_c_And(const LHS &L, const RHS &R) {
+ return m_CombineOr(m_And(L, R), m_And(R, L));
+}
+
+/// \brief Matches an Or with LHS and RHS in either order.
+template<typename LHS, typename RHS>
+inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::Or>,
+ BinaryOp_match<RHS, LHS, Instruction::Or>>
+m_c_Or(const LHS &L, const RHS &R) {
+ return m_CombineOr(m_Or(L, R), m_Or(R, L));
+}
+
+/// \brief Matches an Xor with LHS and RHS in either order.
+template<typename LHS, typename RHS>
+inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::Xor>,
+ BinaryOp_match<RHS, LHS, Instruction::Xor>>
+m_c_Xor(const LHS &L, const RHS &R) {
+ return m_CombineOr(m_Xor(L, R), m_Xor(R, L));
+}
+
} // end namespace PatternMatch
} // end namespace llvm
Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=266939&r1=266938&r2=266939&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Wed Apr 20 19:53:14 2016
@@ -2613,21 +2613,48 @@ static Value *SimplifyICmpInst(unsigned
}
}
- // icmp pred (or X, Y), X
- if (LBO && match(LBO, m_CombineOr(m_Or(m_Value(), m_Specific(RHS)),
- m_Or(m_Specific(RHS), m_Value())))) {
- if (Pred == ICmpInst::ICMP_ULT)
- return getFalse(ITy);
- if (Pred == ICmpInst::ICMP_UGE)
- return getTrue(ITy);
- }
- // icmp pred X, (or X, Y)
- if (RBO && match(RBO, m_CombineOr(m_Or(m_Value(), m_Specific(LHS)),
- m_Or(m_Specific(LHS), m_Value())))) {
- if (Pred == ICmpInst::ICMP_ULE)
- return getTrue(ITy);
- if (Pred == ICmpInst::ICMP_UGT)
- return getFalse(ITy);
+ {
+ Value *Y = nullptr;
+ // icmp pred (or X, Y), X
+ if (LBO && match(LBO, m_c_Or(m_Value(Y), m_Specific(RHS)))) {
+ if (Pred == ICmpInst::ICMP_ULT)
+ return getFalse(ITy);
+ if (Pred == ICmpInst::ICMP_UGE)
+ return getTrue(ITy);
+
+ if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SGE) {
+ bool RHSKnownNonNegative, RHSKnownNegative;
+ bool YKnownNonNegative, YKnownNegative;
+ ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, Q.DL, 0,
+ Q.AC, Q.CxtI, Q.DT);
+ ComputeSignBit(Y, YKnownNonNegative, YKnownNegative, Q.DL, 0, Q.AC,
+ Q.CxtI, Q.DT);
+ if (RHSKnownNonNegative && YKnownNegative)
+ return Pred == ICmpInst::ICMP_SLT ? getTrue(ITy) : getFalse(ITy);
+ if (RHSKnownNegative || YKnownNonNegative)
+ return Pred == ICmpInst::ICMP_SLT ? getFalse(ITy) : getTrue(ITy);
+ }
+ }
+ // icmp pred X, (or X, Y)
+ if (RBO && match(RBO, m_c_Or(m_Value(Y), m_Specific(LHS)))) {
+ if (Pred == ICmpInst::ICMP_ULE)
+ return getTrue(ITy);
+ if (Pred == ICmpInst::ICMP_UGT)
+ return getFalse(ITy);
+
+ if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLE) {
+ bool LHSKnownNonNegative, LHSKnownNegative;
+ bool YKnownNonNegative, YKnownNegative;
+ ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.DL, 0,
+ Q.AC, Q.CxtI, Q.DT);
+ ComputeSignBit(Y, YKnownNonNegative, YKnownNegative, Q.DL, 0, Q.AC,
+ Q.CxtI, Q.DT);
+ if (LHSKnownNonNegative && YKnownNegative)
+ return Pred == ICmpInst::ICMP_SGT ? getTrue(ITy) : getFalse(ITy);
+ if (LHSKnownNegative || YKnownNonNegative)
+ return Pred == ICmpInst::ICMP_SGT ? getFalse(ITy) : getTrue(ITy);
+ }
+ }
}
// icmp pred (and X, Y), X
Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=266939&r1=266938&r2=266939&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Wed Apr 20 19:53:14 2016
@@ -195,6 +195,14 @@ bool llvm::isKnownPositive(Value *V, con
isKnownNonZero(V, DL, Depth, AC, CxtI, DT);
}
+bool llvm::isKnownNegative(Value *V, const DataLayout &DL, unsigned Depth,
+ AssumptionCache *AC, const Instruction *CxtI,
+ const DominatorTree *DT) {
+ bool NonNegative, Negative;
+ ComputeSignBit(V, NonNegative, Negative, DL, Depth, AC, CxtI, DT);
+ return Negative;
+}
+
static bool isKnownNonEqual(Value *V1, Value *V2, const Query &Q);
bool llvm::isKnownNonEqual(Value *V1, Value *V2, const DataLayout &DL,
@@ -508,34 +516,6 @@ bool llvm::isValidAssumeForContext(const
return ::isValidAssumeForContext(const_cast<Instruction *>(I), CxtI, DT);
}
-template<typename LHS, typename RHS>
-inline match_combine_or<CmpClass_match<LHS, RHS, ICmpInst, ICmpInst::Predicate>,
- CmpClass_match<RHS, LHS, ICmpInst, ICmpInst::Predicate>>
-m_c_ICmp(ICmpInst::Predicate &Pred, const LHS &L, const RHS &R) {
- return m_CombineOr(m_ICmp(Pred, L, R), m_ICmp(Pred, R, L));
-}
-
-template<typename LHS, typename RHS>
-inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::And>,
- BinaryOp_match<RHS, LHS, Instruction::And>>
-m_c_And(const LHS &L, const RHS &R) {
- return m_CombineOr(m_And(L, R), m_And(R, L));
-}
-
-template<typename LHS, typename RHS>
-inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::Or>,
- BinaryOp_match<RHS, LHS, Instruction::Or>>
-m_c_Or(const LHS &L, const RHS &R) {
- return m_CombineOr(m_Or(L, R), m_Or(R, L));
-}
-
-template<typename LHS, typename RHS>
-inline match_combine_or<BinaryOp_match<LHS, RHS, Instruction::Xor>,
- BinaryOp_match<RHS, LHS, Instruction::Xor>>
-m_c_Xor(const LHS &L, const RHS &R) {
- return m_CombineOr(m_Xor(L, R), m_Xor(R, L));
-}
-
static void computeKnownBitsFromAssume(Value *V, APInt &KnownZero,
APInt &KnownOne, unsigned Depth,
const Query &Q) {
Modified: llvm/trunk/test/Transforms/InstSimplify/compare.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/compare.ll?rev=266939&r1=266938&r2=266939&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/compare.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/compare.ll Wed Apr 20 19:53:14 2016
@@ -1203,3 +1203,140 @@ define i1 @tautological9(i32 %x) {
; CHECK-LABEL: @tautological9(
; CHECK: ret i1 true
}
+
+declare void @helper_i1(i1)
+; Series of tests for icmp s[lt|ge] (or A, B), A and icmp s[gt|le] A, (or A, B)
+define void @icmp_slt_sge_or(i32 %Ax, i32 %Bx) {
+; 'p' for positive, 'n' for negative, 'x' for potentially either.
+; %D is 'icmp slt (or A, B), A'
+; %E is 'icmp sge (or A, B), A' making it the not of %D
+; %F is 'icmp sgt A, (or A, B)' making it the same as %D
+; %G is 'icmp sle A, (or A, B)' making it the not of %D
+ %Aneg = or i32 %Ax, 2147483648
+ %Apos = and i32 %Ax, 2147483647
+ %Bneg = or i32 %Bx, 2147483648
+ %Bpos = and i32 %Bx, 2147483647
+
+ %Cpp = or i32 %Apos, %Bpos
+ %Dpp = icmp slt i32 %Cpp, %Apos
+ %Epp = icmp sge i32 %Cpp, %Apos
+ %Fpp = icmp sgt i32 %Apos, %Cpp
+ %Gpp = icmp sle i32 %Apos, %Cpp
+ %Cpx = or i32 %Apos, %Bx
+ %Dpx = icmp slt i32 %Cpx, %Apos
+ %Epx = icmp sge i32 %Cpx, %Apos
+ %Fpx = icmp sgt i32 %Apos, %Cpx
+ %Gpx = icmp sle i32 %Apos, %Cpx
+ %Cpn = or i32 %Apos, %Bneg
+ %Dpn = icmp slt i32 %Cpn, %Apos
+ %Epn = icmp sge i32 %Cpn, %Apos
+ %Fpn = icmp sgt i32 %Apos, %Cpn
+ %Gpn = icmp sle i32 %Apos, %Cpn
+
+ %Cxp = or i32 %Ax, %Bpos
+ %Dxp = icmp slt i32 %Cxp, %Ax
+ %Exp = icmp sge i32 %Cxp, %Ax
+ %Fxp = icmp sgt i32 %Ax, %Cxp
+ %Gxp = icmp sle i32 %Ax, %Cxp
+ %Cxx = or i32 %Ax, %Bx
+ %Dxx = icmp slt i32 %Cxx, %Ax
+ %Exx = icmp sge i32 %Cxx, %Ax
+ %Fxx = icmp sgt i32 %Ax, %Cxx
+ %Gxx = icmp sle i32 %Ax, %Cxx
+ %Cxn = or i32 %Ax, %Bneg
+ %Dxn = icmp slt i32 %Cxn, %Ax
+ %Exn = icmp sge i32 %Cxn, %Ax
+ %Fxn = icmp sgt i32 %Ax, %Cxn
+ %Gxn = icmp sle i32 %Ax, %Cxn
+
+ %Cnp = or i32 %Aneg, %Bpos
+ %Dnp = icmp slt i32 %Cnp, %Aneg
+ %Enp = icmp sge i32 %Cnp, %Aneg
+ %Fnp = icmp sgt i32 %Aneg, %Cnp
+ %Gnp = icmp sle i32 %Aneg, %Cnp
+ %Cnx = or i32 %Aneg, %Bx
+ %Dnx = icmp slt i32 %Cnx, %Aneg
+ %Enx = icmp sge i32 %Cnx, %Aneg
+ %Fnx = icmp sgt i32 %Aneg, %Cnx
+ %Gnx = icmp sle i32 %Aneg, %Cnx
+ %Cnn = or i32 %Aneg, %Bneg
+ %Dnn = icmp slt i32 %Cnn, %Aneg
+ %Enn = icmp sge i32 %Cnn, %Aneg
+ %Fnn = icmp sgt i32 %Aneg, %Cnn
+ %Gnn = icmp sle i32 %Aneg, %Cnn
+
+ call void @helper_i1(i1 %Dpp)
+ call void @helper_i1(i1 %Epp)
+ call void @helper_i1(i1 %Fpp)
+ call void @helper_i1(i1 %Gpp)
+ call void @helper_i1(i1 %Dpx)
+ call void @helper_i1(i1 %Epx)
+ call void @helper_i1(i1 %Fpx)
+ call void @helper_i1(i1 %Gpx)
+ call void @helper_i1(i1 %Dpn)
+ call void @helper_i1(i1 %Epn)
+ call void @helper_i1(i1 %Fpn)
+ call void @helper_i1(i1 %Gpn)
+ call void @helper_i1(i1 %Dxp)
+ call void @helper_i1(i1 %Exp)
+ call void @helper_i1(i1 %Fxp)
+ call void @helper_i1(i1 %Gxp)
+ call void @helper_i1(i1 %Dxx)
+ call void @helper_i1(i1 %Exx)
+ call void @helper_i1(i1 %Fxx)
+ call void @helper_i1(i1 %Gxx)
+ call void @helper_i1(i1 %Dxn)
+ call void @helper_i1(i1 %Exn)
+ call void @helper_i1(i1 %Fxn)
+ call void @helper_i1(i1 %Gxn)
+ call void @helper_i1(i1 %Dnp)
+ call void @helper_i1(i1 %Enp)
+ call void @helper_i1(i1 %Fnp)
+ call void @helper_i1(i1 %Gnp)
+ call void @helper_i1(i1 %Dnx)
+ call void @helper_i1(i1 %Enx)
+ call void @helper_i1(i1 %Fnx)
+ call void @helper_i1(i1 %Gnx)
+ call void @helper_i1(i1 %Dnn)
+ call void @helper_i1(i1 %Enn)
+ call void @helper_i1(i1 %Fnn)
+ call void @helper_i1(i1 %Gnn)
+; CHECK-LABEL: @icmp_slt_sge_or
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 %Dpx)
+; CHECK: call void @helper_i1(i1 %Epx)
+; CHECK: call void @helper_i1(i1 %Fpx)
+; CHECK: call void @helper_i1(i1 %Gpx)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 %Dxx)
+; CHECK: call void @helper_i1(i1 %Exx)
+; CHECK: call void @helper_i1(i1 %Fxx)
+; CHECK: call void @helper_i1(i1 %Gxx)
+; CHECK: call void @helper_i1(i1 %Dxn)
+; CHECK: call void @helper_i1(i1 %Exn)
+; CHECK: call void @helper_i1(i1 %Fxn)
+; CHECK: call void @helper_i1(i1 %Gxn)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+; CHECK: call void @helper_i1(i1 false)
+; CHECK: call void @helper_i1(i1 true)
+ ret void
+}
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