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Rip min/max pattern matching out of InstCombine and into

Browse Source 
ValueTracking.

This matching functionality is useful in more than just InstCombine, so
make it available in ValueTracking.

NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236998 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy
2015-05-11 14:42:20 +00:00
parent 0a62359646
commit 2605531fe8
4 changed files with 100 additions and 99 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
include/llvm/Analysis/ValueTracking.h
View File

@@ -262,6 +262,21 @@ namespace llvm {
AssumptionCache *AC, AssumptionCache *AC,
const Instruction *CxtI, const Instruction *CxtI,
const DominatorTree *DT); const DominatorTree *DT);
/// \brief Specific patterns of select instructions we can match.
enum SelectPatternFlavor {
SPF_UNKNOWN = 0,
SPF_SMIN, // Signed minimum
SPF_UMIN, // Unsigned minimum
SPF_SMAX, // Signed maximum
SPF_UMAX, // Unsigned maximum
SPF_ABS, // Absolute value
SPF_NABS // Negated absolute value
};
/// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
/// and providing the out parameter results if we successfully match.
SelectPatternFlavor matchSelectPattern(Value *V, Value *&LHS, Value *&RHS);
} // end namespace llvm } // end namespace llvm
#endif #endif

81
lib/Analysis/ValueTracking.cpp
View File

@@ -3204,3 +3204,84 @@ OverflowResult llvm::computeOverflowForUnsignedAdd(Value *LHS, Value *RHS,
return OverflowResult::MayOverflow; return OverflowResult::MayOverflow;
} }
SelectPatternFlavor llvm::matchSelectPattern(Value *V,
Value *&LHS, Value *&RHS) {
SelectInst *SI = dyn_cast<SelectInst>(V);
if (!SI) return SPF_UNKNOWN;
ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
if (!ICI) return SPF_UNKNOWN;
ICmpInst::Predicate Pred = ICI->getPredicate();
Value *CmpLHS = ICI->getOperand(0);
Value *CmpRHS = ICI->getOperand(1);
Value *TrueVal = SI->getTrueValue();
Value *FalseVal = SI->getFalseValue();
LHS = CmpLHS;
RHS = CmpRHS;
// (icmp X, Y) ? X : Y
if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
switch (Pred) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMAX;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMAX;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMIN;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMIN;
}
}
// (icmp X, Y) ? Y : X
if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
switch (Pred) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMIN;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMIN;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMAX;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMAX;
}
}
if (ConstantInt *C1 = dyn_cast<ConstantInt>(CmpRHS)) {
if ((CmpLHS == TrueVal && match(FalseVal, m_Neg(m_Specific(CmpLHS)))) ||
(CmpLHS == FalseVal && match(TrueVal, m_Neg(m_Specific(CmpLHS))))) {
// ABS(X) ==> (X >s 0) ? X : -X and (X >s -1) ? X : -X
// NABS(X) ==> (X >s 0) ? -X : X and (X >s -1) ? -X : X
if (Pred == ICmpInst::ICMP_SGT && (C1->isZero() || C1->isMinusOne())) {
return (CmpLHS == TrueVal) ? SPF_ABS : SPF_NABS;
}
// ABS(X) ==> (X <s 0) ? -X : X and (X <s 1) ? -X : X
// NABS(X) ==> (X <s 0) ? X : -X and (X <s 1) ? X : -X
if (Pred == ICmpInst::ICMP_SLT && (C1->isZero() || C1->isOne())) {
return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS;
}
}
// Y >s C ? ~Y : ~C == ~Y <s ~C ? ~Y : ~C = SMIN(~Y, ~C)
if (const auto *C2 = dyn_cast<ConstantInt>(FalseVal)) {
if (C1->getType() == C2->getType() && ~C1->getValue() == C2->getValue() &&
(match(TrueVal, m_Not(m_Specific(CmpLHS))) ||
match(CmpLHS, m_Not(m_Specific(TrueVal))))) {
LHS = TrueVal;
RHS = FalseVal;
return SPF_SMIN;
}
}
}
// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
return SPF_UNKNOWN;
}

11
lib/Transforms/InstCombine/InstCombineInternal.h
View File

@@ -39,17 +39,6 @@ class DbgDeclareInst;
class MemIntrinsic; class MemIntrinsic;
class MemSetInst; class MemSetInst;
/// \brief Specific patterns of select instructions we can match.
enum SelectPatternFlavor {
SPF_UNKNOWN = 0,
SPF_SMIN,
SPF_UMIN,
SPF_SMAX,
SPF_UMAX,
SPF_ABS,
SPF_NABS
};
/// \brief Assign a complexity or rank value to LLVM Values. /// \brief Assign a complexity or rank value to LLVM Values.
/// ///
/// This routine maps IR values to various complexity ranks: /// This routine maps IR values to various complexity ranks:

92
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@@ -14,6 +14,7 @@
#include "InstCombineInternal.h" #include "InstCombineInternal.h"
#include "llvm/Analysis/ConstantFolding.h" #include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/PatternMatch.h" #include "llvm/IR/PatternMatch.h"
using namespace llvm; using namespace llvm;
using namespace PatternMatch; using namespace PatternMatch;
@@ -60,91 +61,6 @@ static Value *generateMinMaxSelectPattern(InstCombiner::BuilderTy *Builder,
return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B); return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B);
} }
/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
/// returning the kind and providing the out parameter results if we
/// successfully match.
static SelectPatternFlavor
MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
SelectInst *SI = dyn_cast<SelectInst>(V);
if (!SI) return SPF_UNKNOWN;
ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
if (!ICI) return SPF_UNKNOWN;
ICmpInst::Predicate Pred = ICI->getPredicate();
Value *CmpLHS = ICI->getOperand(0);
Value *CmpRHS = ICI->getOperand(1);
Value *TrueVal = SI->getTrueValue();
Value *FalseVal = SI->getFalseValue();
LHS = CmpLHS;
RHS = CmpRHS;
// (icmp X, Y) ? X : Y
if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
switch (Pred) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMAX;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMAX;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMIN;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMIN;
}
}
// (icmp X, Y) ? Y : X
if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
switch (Pred) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMIN;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMIN;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMAX;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMAX;
}
}
if (ConstantInt *C1 = dyn_cast<ConstantInt>(CmpRHS)) {
if ((CmpLHS == TrueVal && match(FalseVal, m_Neg(m_Specific(CmpLHS)))) ||
(CmpLHS == FalseVal && match(TrueVal, m_Neg(m_Specific(CmpLHS))))) {
// ABS(X) ==> (X >s 0) ? X : -X and (X >s -1) ? X : -X
// NABS(X) ==> (X >s 0) ? -X : X and (X >s -1) ? -X : X
if (Pred == ICmpInst::ICMP_SGT && (C1->isZero() || C1->isMinusOne())) {
return (CmpLHS == TrueVal) ? SPF_ABS : SPF_NABS;
}
// ABS(X) ==> (X <s 0) ? -X : X and (X <s 1) ? -X : X
// NABS(X) ==> (X <s 0) ? X : -X and (X <s 1) ? X : -X
if (Pred == ICmpInst::ICMP_SLT && (C1->isZero() || C1->isOne())) {
return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS;
}
}
// Y >s C ? ~Y : ~C == ~Y <s ~C ? ~Y : ~C = SMIN(~Y, ~C)
if (const auto *C2 = dyn_cast<ConstantInt>(FalseVal)) {
if (C1->getType() == C2->getType() && ~C1->getValue() == C2->getValue() &&
(match(TrueVal, m_Not(m_Specific(CmpLHS))) ||
match(CmpLHS, m_Not(m_Specific(TrueVal))))) {
LHS = TrueVal;
RHS = FalseVal;
return SPF_SMIN;
}
}
}
// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
return SPF_UNKNOWN;
}
/// GetSelectFoldableOperands - We want to turn code that looks like this: /// GetSelectFoldableOperands - We want to turn code that looks like this:
/// %C = or %A, %B /// %C = or %A, %B
/// %D = select %cond, %C, %A /// %D = select %cond, %C, %A
@@ -1243,18 +1159,18 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return FoldI; return FoldI;
Value *LHS, *RHS, *LHS2, *RHS2; Value *LHS, *RHS, *LHS2, *RHS2;
SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS); SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS);
// MAX(MAX(a, b), a) -> MAX(a, b) // MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b) // MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a // MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a // MIN(MAX(a, b), a) -> a
if (SPF) { if (SPF) {
if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2)) if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2, if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
SI, SPF, RHS)) SI, SPF, RHS))
return R; return R;
if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2)) if (SelectPatternFlavor SPF2 = matchSelectPattern(RHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2, if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
SI, SPF, LHS)) SI, SPF, LHS))
return R; return R;