#include "llvm/CallGraphSCCPass.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CaptureTracking.h"
namespace {
struct FunctionAttrs : public CallGraphSCCPass {
static char ID; // Pass identification, replacement for typeid
- FunctionAttrs() : CallGraphSCCPass(ID) {
+ FunctionAttrs() : CallGraphSCCPass(ID), AA(0) {
initializeFunctionAttrsPass(*PassRegistry::getPassRegistry());
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
+ AU.addRequired<AliasAnalysis>();
CallGraphSCCPass::getAnalysisUsage(AU);
}
- bool PointsToLocalOrConstantMemory(Value *V);
+ private:
+ AliasAnalysis *AA;
};
}
Pass *llvm::createFunctionAttrsPass() { return new FunctionAttrs(); }
-/// PointsToLocalOrConstantMemory - Returns whether the given pointer value
-/// points to memory that is local to the function, with global constants being
-/// considered local to all functions.
-bool FunctionAttrs::PointsToLocalOrConstantMemory(Value *V) {
- SmallVector<Value*, 16> Worklist;
- unsigned MaxLookup = 8;
-
- Worklist.push_back(V);
-
- do {
- V = Worklist.pop_back_val()->getUnderlyingObject();
-
- // An alloca instruction defines local memory.
- if (isa<AllocaInst>(V))
- continue;
-
- // A global constant counts as local memory for our purposes.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
- if (!GV->isConstant())
- return false;
- continue;
- }
-
- // If both select values point to local memory, then so does the select.
- if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
- Worklist.push_back(SI->getTrueValue());
- Worklist.push_back(SI->getFalseValue());
- continue;
- }
-
- // If all values incoming to a phi node point to local memory, then so does
- // the phi.
- if (PHINode *PN = dyn_cast<PHINode>(V)) {
- // Don't bother inspecting phi nodes with many operands.
- if (PN->getNumIncomingValues() > MaxLookup)
- return false;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- Worklist.push_back(PN->getIncomingValue(i));
- continue;
- }
-
- return false;
- } while (!Worklist.empty() && --MaxLookup);
-
- return Worklist.empty();
-}
-
/// AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
SmallPtrSet<Function*, 8> SCCNodes;
// External node - may write memory. Just give up.
return false;
- if (F->doesNotAccessMemory())
+ AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(F);
+ if (MRB == AliasAnalysis::DoesNotAccessMemory)
// Already perfect!
continue;
// Definitions with weak linkage may be overridden at linktime with
// something that writes memory, so treat them like declarations.
if (F->isDeclaration() || F->mayBeOverridden()) {
- if (!F->onlyReadsMemory())
+ if (!AliasAnalysis::onlyReadsMemory(MRB))
// May write memory. Just give up.
return false;
// Some instructions can be ignored even if they read or write memory.
// Detect these now, skipping to the next instruction if one is found.
CallSite CS(cast<Value>(I));
- if (CS && CS.getCalledFunction()) {
+ if (CS) {
// Ignore calls to functions in the same SCC.
- if (SCCNodes.count(CS.getCalledFunction()))
+ if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
continue;
- // Ignore intrinsics that only access local memory.
- if (unsigned id = CS.getCalledFunction()->getIntrinsicID())
- if (AliasAnalysis::getIntrinsicModRefBehavior(id) ==
- AliasAnalysis::AccessesArguments) {
- // Check that all pointer arguments point to local memory.
+ AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(CS);
+ // If the call doesn't access arbitrary memory, we may be able to
+ // figure out something.
+ if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
+ // If the call does access argument pointees, check each argument.
+ if (AliasAnalysis::doesAccessArgPointees(MRB))
+ // Check whether all pointer arguments point to local memory, and
+ // ignore calls that only access local memory.
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
CI != CE; ++CI) {
Value *Arg = *CI;
- if (Arg->getType()->isPointerTy() &&
- !PointsToLocalOrConstantMemory(Arg))
- // Writes memory. Just give up.
- return false;
+ if (Arg->getType()->isPointerTy()) {
+ AliasAnalysis::Location Loc(Arg,
+ AliasAnalysis::UnknownSize,
+ I->getMetadata(LLVMContext::MD_tbaa));
+ if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true)) {
+ if (MRB & AliasAnalysis::Mod)
+ // Writes non-local memory. Give up.
+ return false;
+ if (MRB & AliasAnalysis::Ref)
+ // Ok, it reads non-local memory.
+ ReadsMemory = true;
+ }
+ }
}
- // Only reads and writes local memory.
- continue;
- }
+ continue;
+ }
+ // The call could access any memory. If that includes writes, give up.
+ if (MRB & AliasAnalysis::Mod)
+ return false;
+ // If it reads, note it.
+ if (MRB & AliasAnalysis::Ref)
+ ReadsMemory = true;
+ continue;
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// Ignore non-volatile loads from local memory.
- if (!LI->isVolatile() &&
- PointsToLocalOrConstantMemory(LI->getPointerOperand()))
- continue;
+ if (!LI->isVolatile()) {
+ AliasAnalysis::Location Loc = AA->getLocation(LI);
+ if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
+ continue;
+ }
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
// Ignore non-volatile stores to local memory.
- if (!SI->isVolatile() &&
- PointsToLocalOrConstantMemory(SI->getPointerOperand()))
+ if (!SI->isVolatile()) {
+ AliasAnalysis::Location Loc = AA->getLocation(SI);
+ if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
+ continue;
+ }
+ } else if (VAArgInst *VI = dyn_cast<VAArgInst>(I)) {
+ // Ignore vaargs on local memory.
+ AliasAnalysis::Location Loc = AA->getLocation(VI);
+ if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
continue;
}
}
bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
+ AA = &getAnalysis<AliasAnalysis>();
+
bool Changed = AddReadAttrs(SCC);
Changed |= AddNoCaptureAttrs(SCC);
Changed |= AddNoAliasAttrs(SCC);
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