//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "correlated-value-propagation"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LazyValueInfo.h"
-#include "llvm/Support/CFG.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/Statistic.h"
using namespace llvm;
+#define DEBUG_TYPE "correlated-value-propagation"
+
STATISTIC(NumPhis, "Number of phis propagated");
STATISTIC(NumSelects, "Number of selects propagated");
STATISTIC(NumMemAccess, "Number of memory access targets propagated");
initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
}
- bool runOnFunction(Function &F);
+ bool runOnFunction(Function &F) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LazyValueInfo>();
}
};
if (S->getType()->isVectorTy()) return false;
if (isa<Constant>(S->getOperand(0))) return false;
- Constant *C = LVI->getConstant(S->getOperand(0), S->getParent());
+ Constant *C = LVI->getConstant(S->getOperand(0), S->getParent(), S);
if (!C) return false;
ConstantInt *CI = dyn_cast<ConstantInt>(C);
Value *Incoming = P->getIncomingValue(i);
if (isa<Constant>(Incoming)) continue;
- Constant *C = LVI->getConstantOnEdge(P->getIncomingValue(i),
- P->getIncomingBlock(i),
- BB);
- if (!C) continue;
+ Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB, P);
+
+ // Look if the incoming value is a select with a scalar condition for which
+ // LVI can tells us the value. In that case replace the incoming value with
+ // the appropriate value of the select. This often allows us to remove the
+ // select later.
+ if (!V) {
+ SelectInst *SI = dyn_cast<SelectInst>(Incoming);
+ if (!SI) continue;
+
+ Value *Condition = SI->getCondition();
+ if (!Condition->getType()->isVectorTy()) {
+ if (Constant *C = LVI->getConstantOnEdge(
+ Condition, P->getIncomingBlock(i), BB, P)) {
+ if (C->isOneValue()) {
+ V = SI->getTrueValue();
+ } else if (C->isZeroValue()) {
+ V = SI->getFalseValue();
+ }
+ // Once LVI learns to handle vector types, we could also add support
+ // for vector type constants that are not all zeroes or all ones.
+ }
+ }
+
+ // Look if the select has a constant but LVI tells us that the incoming
+ // value can never be that constant. In that case replace the incoming
+ // value with the other value of the select. This often allows us to
+ // remove the select later.
+ if (!V) {
+ Constant *C = dyn_cast<Constant>(SI->getFalseValue());
+ if (!C) continue;
+
+ if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
+ P->getIncomingBlock(i), BB, P) !=
+ LazyValueInfo::False)
+ continue;
+ V = SI->getTrueValue();
+ }
+
+ DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
+ }
- P->setIncomingValue(i, C);
+ P->setIncomingValue(i, V);
Changed = true;
}
- if (Value *V = SimplifyInstruction(P)) {
+ // FIXME: Provide TLI, DT, AT to SimplifyInstruction.
+ const DataLayout &DL = BB->getModule()->getDataLayout();
+ if (Value *V = SimplifyInstruction(P, DL)) {
P->replaceAllUsesWith(V);
P->eraseFromParent();
Changed = true;
}
bool CorrelatedValuePropagation::processMemAccess(Instruction *I) {
- Value *Pointer = 0;
+ Value *Pointer = nullptr;
if (LoadInst *L = dyn_cast<LoadInst>(I))
Pointer = L->getPointerOperand();
else
if (isa<Constant>(Pointer)) return false;
- Constant *C = LVI->getConstant(Pointer, I->getParent());
+ Constant *C = LVI->getConstant(Pointer, I->getParent(), I);
if (!C) return false;
++NumMemAccess;
if (PI == PE) return false;
LazyValueInfo::Tristate Result = LVI->getPredicateOnEdge(C->getPredicate(),
- C->getOperand(0), Op1, *PI, C->getParent());
+ C->getOperand(0), Op1, *PI,
+ C->getParent(), C);
if (Result == LazyValueInfo::Unknown) return false;
++PI;
while (PI != PE) {
LazyValueInfo::Tristate Res = LVI->getPredicateOnEdge(C->getPredicate(),
- C->getOperand(0), Op1, *PI, C->getParent());
+ C->getOperand(0), Op1, *PI,
+ C->getParent(), C);
if (Res != Result) return false;
++PI;
}
// Analyse each switch case in turn. This is done in reverse order so that
// removing a case doesn't cause trouble for the iteration.
bool Changed = false;
- for (SwitchInst::CaseIt CI = SI->caseEnd(), CE = SI->caseBegin(); CI-- != CE;
+ for (SwitchInst::CaseIt CI = SI->case_end(), CE = SI->case_begin(); CI-- != CE;
) {
ConstantInt *Case = CI.getCaseValue();
for (pred_iterator PI = PB; PI != PE; ++PI) {
// Is the switch condition equal to the case value?
LazyValueInfo::Tristate Value = LVI->getPredicateOnEdge(CmpInst::ICMP_EQ,
- Cond, Case, *PI, BB);
+ Cond, Case, *PI,
+ BB, SI);
// Give up on this case if nothing is known.
if (Value == LazyValueInfo::Unknown) {
State = LazyValueInfo::Unknown;
// This case never fires - remove it.
CI.getCaseSuccessor()->removePredecessor(BB);
SI->removeCase(CI); // Does not invalidate the iterator.
+
+ // The condition can be modified by removePredecessor's PHI simplification
+ // logic.
+ Cond = SI->getCondition();
+
++NumDeadCases;
Changed = true;
} else if (State == LazyValueInfo::True) {
}
bool CorrelatedValuePropagation::runOnFunction(Function &F) {
+ if (skipOptnoneFunction(F))
+ return false;
+
LVI = &getAnalysis<LazyValueInfo>();
bool FnChanged = false;
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