[llvm-commits] CVS: llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp
Nick Lewycky
nicholas at mxc.ca
Tue Aug 29 19:47:02 PDT 2006
Changes in directory llvm/lib/Transforms/Scalar:
PredicateSimplifier.cpp updated: 1.1 -> 1.2
---
Log message:
Move to using the EquivalenceClass ADT. Removes SynSets.
If a branch's condition has become a ConstantBool, simplify it immediately.
Removing the edge saves work and exposes up more optimization opportunities
in the pass.
Add support for SelectInst.
---
Diffs of the changes: (+92 -165)
PredicateSimplifier.cpp | 257 +++++++++++++++++-------------------------------
1 files changed, 92 insertions(+), 165 deletions(-)
Index: llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp
diff -u llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp:1.1 llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp:1.2
--- llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp:1.1 Mon Aug 28 17:44:55 2006
+++ llvm/lib/Transforms/Scalar/PredicateSimplifier.cpp Tue Aug 29 21:46:48 2006
@@ -23,26 +23,20 @@
//===------------------------------------------------------------------===//
//
// This optimization works by substituting %q for %p when protected by a
-// conditional that assures us of that fact. Equivalent variables are
-// called SynSets; sets of synonyms. We maintain a mapping from Value *
-// to the SynSet, and the SynSet maintains the best canonical form of the
-// Value.
-//
-// Properties are stored as relationships between two SynSets.
+// conditional that assures us of that fact. Properties are stored as
+// relationships between two values.
//
//===------------------------------------------------------------------===//
// TODO:
-// * Handle SelectInst
-// * Switch to EquivalenceClasses ADT
// * Check handling of NAN in floating point types
-// * Don't descend into false side of branches with ConstantBool condition.
#define DEBUG_TYPE "predsimplify"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
+#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Dominators.h"
@@ -55,9 +49,11 @@
Statistic<>
NumVarsReplaced("predsimplify", "Number of argument substitutions");
Statistic<>
- NumResolved("predsimplify", "Number of instruction substitutions");
+ NumInstruction("predsimplify", "Number of instructions removed");
Statistic<>
NumSwitchCases("predsimplify", "Number of switch cases removed");
+ Statistic<>
+ NumBranches("predsimplify", "Number of branches made unconditional");
/// Used for choosing the canonical Value in a synonym set.
/// Leaves the better one in V1. Returns whether a swap took place.
@@ -89,10 +85,8 @@
/// and fast lookup. Also stores the set of inequality relationships.
class PropertySet {
struct Property;
+ class EquivalenceClasses<Value *> union_find;
public:
- typedef unsigned SynSet;
- typedef std::map<Value*, unsigned>::iterator SynonymIterator;
- typedef std::map<Value*, unsigned>::const_iterator ConstSynonymIterator;
typedef std::vector<Property>::iterator PropertyIterator;
typedef std::vector<Property>::const_iterator ConstPropertyIterator;
@@ -107,133 +101,44 @@
}
Value *lookup(Value *V) const {
- ConstSynonymIterator SI = SynonymMap.find(V);
- if (SI == SynonymMap.end()) return NULL;
-
- return Synonyms[SI->second];
- }
-
- Value *lookup(SynSet SS) const {
- assert(SS < Synonyms.size());
- return Synonyms[SS];
- }
-
- // Find a SynSet for a given Value.
- //
- // Given the Value *V sets SS to a valid SynSet. Returns true if it
- // found it.
- bool findSynSet(Value *V, SynSet &SS) const {
- ConstSynonymIterator SI = SynonymMap.find(V);
- if (SI != SynonymMap.end()) {
- SS = SI->second;
- return true;
- }
-
- std::vector<Value *>::const_iterator I =
- std::find(Synonyms.begin(), Synonyms.end(), V);
- if (I != Synonyms.end()) {
- SS = I-Synonyms.begin();
- return true;
- }
-
- return false;
+ EquivalenceClasses<Value *>::member_iterator SI =
+ union_find.findLeader(V);
+ if (SI == union_find.member_end()) return NULL;
+ return *SI;
}
bool empty() const {
- return Synonyms.empty();
+ return union_find.empty();
}
void addEqual(Value *V1, Value *V2) {
order(V1, V2);
if (isa<Constant>(V2)) return; // refuse to set false == true.
- V1 = canonicalize(V1);
- V2 = canonicalize(V2);
-
- if (V1 == V2) return; // already equivalent.
-
- SynSet I1, I2;
- bool F1 = findSynSet(V1, I1),
- F2 = findSynSet(V2, I2);
-
- DEBUG(std::cerr << "V1: " << *V1 << " I1: " << I1
- << " F1: " << F1 << "\n");
- DEBUG(std::cerr << "V2: " << *V2 << " I2: " << I2
- << " F2: " << F2 << "\n");
-
- if (!F1 && !F2) {
- SynSet SS = addSynSet(V1);
- SynonymMap[V1] = SS;
- SynonymMap[V2] = SS;
- }
-
- else if (!F1 && F2) {
- SynonymMap[V1] = I2;
- }
-
- else if (F1 && !F2) {
- SynonymMap[V2] = I1;
- }
-
- else {
- // This is the case where we have two sets, [%a1, %a2, %a3] and
- // [%p1, %p2, %p3] and someone says that %a2 == %p3. We need to
- // combine the two synsets.
-
- // Collapse synonyms of V2 into V1.
- for (SynonymIterator I = SynonymMap.begin(), E = SynonymMap.end();
- I != E; ++I) {
- if (I->second == I2) I->second = I1;
- else if (I->second > I2) --I->second;
- }
-
- // Move Properties
- for (PropertyIterator I = Properties.begin(), E = Properties.end();
- I != E; ++I) {
- if (I->S1 == I2) I->S1 = I1;
- else if (I->S1 > I2) --I->S1;
- if (I->S2 == I2) I->S2 = I1;
- else if (I->S2 > I2) --I->S2;
- }
-
- // Remove the synonym
- Synonyms.erase(Synonyms.begin() + I2);
- }
-
+ union_find.unionSets(V1, V2);
addImpliedProperties(EQ, V1, V2);
}
void addNotEqual(Value *V1, Value *V2) {
DEBUG(std::cerr << "not equal: " << *V1 << " and " << *V2 << "\n");
- bool skip_search = false;
V1 = canonicalize(V1);
V2 = canonicalize(V2);
- SynSet S1, S2;
- if (!findSynSet(V1, S1)) {
- skip_search = true;
- S1 = addSynSet(V1);
- }
- if (!findSynSet(V2, S2)) {
- skip_search = true;
- S2 = addSynSet(V2);
- }
+ // Does the property already exist?
+ for (PropertyIterator I = Properties.begin(), E = Properties.end();
+ I != E; ++I) {
+ if (I->Opcode != NE) continue;
- if (!skip_search) {
- // Does the property already exist?
- for (PropertyIterator I = Properties.begin(), E = Properties.end();
- I != E; ++I) {
- if (I->Opcode != NE) continue;
-
- if ((I->S1 == S1 && I->S2 == S2) ||
- (I->S1 == S2 && I->S2 == S1)) {
- return; // Found.
- }
+ I->V1 = canonicalize(I->V1);
+ I->V2 = canonicalize(I->V2);
+ if ((I->V1 == V1 && I->V2 == V2) ||
+ (I->V1 == V2 && I->V2 == V1)) {
+ return; // Found.
}
}
// Add the property.
- Properties.push_back(Property(NE, S1, S2));
+ Properties.push_back(Property(NE, V1, V2));
addImpliedProperties(NE, V1, V2);
}
@@ -241,17 +146,19 @@
assert(Opcode != EQ && "Can't findProperty on EQ."
"Use the lookup method instead.");
- SynSet S1, S2;
- if (!findSynSet(V1, S1)) return Properties.end();
- if (!findSynSet(V2, S2)) return Properties.end();
+ V1 = lookup(V1);
+ V2 = lookup(V2);
+ if (!V1 || !V2) return Properties.end();
// Does the property already exist?
for (PropertyIterator I = Properties.begin(), E = Properties.end();
I != E; ++I) {
if (I->Opcode != Opcode) continue;
- if ((I->S1 == S1 && I->S2 == S2) ||
- (I->S1 == S2 && I->S2 == S1)) {
+ I->V1 = canonicalize(I->V1);
+ I->V2 = canonicalize(I->V2);
+ if ((I->V1 == V1 && I->V2 == V2) ||
+ (I->V1 == V2 && I->V2 == V1)) {
return I; // Found.
}
}
@@ -263,17 +170,20 @@
assert(Opcode != EQ && "Can't findProperty on EQ."
"Use the lookup method instead.");
- SynSet S1, S2;
- if (!findSynSet(V1, S1)) return Properties.end();
- if (!findSynSet(V2, S2)) return Properties.end();
+ V1 = lookup(V1);
+ V2 = lookup(V2);
+ if (!V1 || !V2) return Properties.end();
// Does the property already exist?
for (ConstPropertyIterator I = Properties.begin(),
E = Properties.end(); I != E; ++I) {
if (I->Opcode != Opcode) continue;
- if ((I->S1 == S1 && I->S2 == S2) ||
- (I->S1 == S2 && I->S2 == S1)) {
+ Value *v1 = lookup(I->V1),
+ *v2 = lookup(I->V2);
+ if (!v1 || !v2) continue;
+ if ((v1 == V1 && v2 == V2) ||
+ (v1 == V2 && v2 == V1)) {
return I; // Found.
}
}
@@ -284,26 +194,21 @@
// Represents Head OP [Tail1, Tail2, ...]
// For example: %x != %a, %x != %b.
struct Property {
- Property(Ops opcode, SynSet s1, SynSet s2)
- : Opcode(opcode), S1(s1), S2(s2)
+ Property(Ops opcode, Value *v1, Value *v2)
+ : Opcode(opcode), V1(v1), V2(v2)
{ assert(opcode != EQ && "Equality belongs in the synonym set,"
"not a property."); }
bool operator<(const Property &rhs) const {
if (Opcode != rhs.Opcode) return Opcode < rhs.Opcode;
- if (S1 != rhs.S1) return S1 < rhs.S1;
- return S2 < rhs.S2;
+ if (V1 != rhs.V1) return V1 < rhs.V1;
+ return V2 < rhs.V2;
}
Ops Opcode;
- SynSet S1, S2;
+ Value *V1, *V2;
};
- SynSet addSynSet(Value *V) {
- Synonyms.push_back(V);
- return Synonyms.size()-1;
- }
-
void add(Ops Opcode, Value *V1, Value *V2, bool invert) {
switch (Opcode) {
case EQ:
@@ -386,19 +291,6 @@
public:
void debug(std::ostream &os) const {
- os << Synonyms.size() << " synsets:\n";
- for (unsigned I = 0, E = Synonyms.size(); I != E; ++I) {
- os << I << ". " << *Synonyms[I] << "\n";
- }
- for (ConstSynonymIterator I = SynonymMap.begin(),E = SynonymMap.end();
- I != E; ++I) {
- os << *I->first << "-> #" << I->second << "\n";
- }
- os << Properties.size() << " properties:\n";
- for (unsigned I = 0, E = Properties.size(); I != E; ++I) {
- os << I << ". (" << Properties[I].Opcode << ","
- << Properties[I].S1 << "," << Properties[I].S2 << ")\n";
- }
}
std::vector<Property> Properties;
@@ -416,6 +308,7 @@
// Try to replace the Use of the instruction with something simpler.
Value *resolve(SetCondInst *SCI, const PropertySet &);
Value *resolve(BinaryOperator *BO, const PropertySet &);
+ Value *resolve(SelectInst *SI, const PropertySet &);
Value *resolve(Value *V, const PropertySet &);
// Used by terminator instructions to proceed from the current basic
@@ -546,6 +439,15 @@
return BO;
}
+Value *PredicateSimplifier::resolve(SelectInst *SI, const PropertySet &KP) {
+ Value *Condition = resolve(SI->getCondition(), KP);
+ if (Condition == ConstantBool::True)
+ return resolve(SI->getTrueValue(), KP);
+ else if (Condition == ConstantBool::False)
+ return resolve(SI->getFalseValue(), KP);
+ return SI;
+}
+
Value *PredicateSimplifier::resolve(Value *V, const PropertySet &KP) {
if (isa<Constant>(V) || isa<BasicBlock>(V) || KP.empty()) return V;
@@ -553,6 +455,8 @@
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(V))
return resolve(BO, KP);
+ else if (SelectInst *SI = dyn_cast<SelectInst>(V))
+ return resolve(SI, KP);
return V;
}
@@ -588,7 +492,7 @@
assert(V && "resolve not supposed to return NULL.");
if (V != I) {
modified = true;
- ++NumResolved;
+ ++NumInstruction;
I->replaceAllUsesWith(V);
I->eraseFromParent();
}
@@ -645,15 +549,31 @@
Value *Condition = BI->getCondition();
+ BasicBlock *TrueDest = BI->getSuccessor(0),
+ *FalseDest = BI->getSuccessor(1);
+
+ if (Condition == ConstantBool::True) {
+ FalseDest->removePredecessor(BI->getParent());
+ BI->setUnconditionalDest(TrueDest);
+ modified = true;
+ ++NumBranches;
+ proceedToSuccessor(KP, Node, DT->getNode(TrueDest));
+ return;
+ } else if (Condition == ConstantBool::False) {
+ TrueDest->removePredecessor(BI->getParent());
+ BI->setUnconditionalDest(FalseDest);
+ modified = true;
+ ++NumBranches;
+ proceedToSuccessor(KP, Node, DT->getNode(FalseDest));
+ return;
+ }
+
PropertySet TrueProperties(KP), FalseProperties(KP);
DEBUG(std::cerr << "true set:\n");
TrueProperties.addEqual(ConstantBool::True, Condition);
DEBUG(std::cerr << "false set:\n");
FalseProperties.addEqual(ConstantBool::False, Condition);
- BasicBlock *TrueDest = BI->getSuccessor(0),
- *FalseDest = BI->getSuccessor(1);
-
PropertySet KPcopy(KP);
proceedToSuccessor(KP, TrueProperties, Node, DT->getNode(TrueDest));
proceedToSuccessor(KPcopy, FalseProperties, Node, DT->getNode(FalseDest));
@@ -665,17 +585,18 @@
// If there's an NEProperty covering this SwitchInst, we may be able to
// eliminate one of the cases.
- PropertySet::SynSet S;
-
- if (KP.findSynSet(Condition, S)) {
+ if (Value *C = KP.lookup(Condition)) {
+ Condition = C;
for (PropertySet::ConstPropertyIterator I = KP.Properties.begin(),
E = KP.Properties.end(); I != E; ++I) {
if (I->Opcode != PropertySet::NE) continue;
- if (I->S1 != S && I->S2 != S) continue;
+ Value *V1 = KP.lookup(I->V1),
+ *V2 = KP.lookup(I->V2);
+ if (V1 != C && V2 != C) continue;
// Is one side a number?
- ConstantInt *CI = dyn_cast<ConstantInt>(KP.lookup(I->S1));
- if (!CI) CI = dyn_cast<ConstantInt>(KP.lookup(I->S2));
+ ConstantInt *CI = dyn_cast<ConstantInt>(KP.lookup(I->V1));
+ if (!CI) CI = dyn_cast<ConstantInt>(KP.lookup(I->V2));
if (CI) {
unsigned i = SI->findCaseValue(CI);
@@ -732,11 +653,17 @@
void PredicateSimplifier::visit(BinaryOperator *BO,
DominatorTree::Node *, PropertySet &KP) {
Instruction::BinaryOps ops = BO->getOpcode();
- if (ops != Instruction::Div && ops != Instruction::Rem) return;
- Value *Divisor = BO->getOperand(1);
- const Type *Ty = cast<Type>(Divisor->getType());
- KP.addNotEqual(Constant::getNullValue(Ty), Divisor);
+ switch (ops) {
+ case Instruction::Div:
+ case Instruction::Rem: {
+ Value *Divisor = BO->getOperand(1);
+ KP.addNotEqual(Constant::getNullValue(Divisor->getType()), Divisor);
+ break;
+ }
+ default:
+ break;
+ }
// Some other things we could do:
// In f=x*y, if x != 1 && y != 1 then f != x && f != y.
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