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BasicAliasAnalysis and FunctionAttrs were both

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doing very similar pointer capture analysis.
Factor out the common logic.  The new version
is from FunctionAttrs since it does a better
job than the version in BasicAliasAnalysis


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62461 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands
2009-01-18 12:19:30 +00:00
parent e3bc6ae92a
commit 8556d2a7f1
4 changed files with 144 additions and 133 deletions
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lib/Transforms/IPO/FunctionAttrs.cpp
+2 -81
View File
@@ -24,7 +24,7 @@
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
@@ -49,9 +49,6 @@ namespace {
// AddNoCaptureAttrs - Deduce nocapture attributes for the SCC.
bool AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC);
// isCaptured - Return true if this pointer value may be captured.
bool isCaptured(Function &F, Value *V);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
CallGraphSCCPass::getAnalysisUsage(AU);
@@ -181,82 +178,6 @@ bool FunctionAttrs::AddReadAttrs(const std::vector<CallGraphNode *> &SCC) {
return MadeChange;
}
/// isCaptured - Return true if this pointer value may be captured.
bool FunctionAttrs::isCaptured(Function &F, Value *V) {
SmallVector<Use*, 16> Worklist;
SmallSet<Use*, 16> Visited;
for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE;
++UI) {
Use *U = &UI.getUse();
Visited.insert(U);
Worklist.push_back(U);
}
while (!Worklist.empty()) {
Use *U = Worklist.pop_back_val();
Instruction *I = cast<Instruction>(U->getUser());
V = U->get();
switch (I->getOpcode()) {
case Instruction::Call:
case Instruction::Invoke: {
CallSite CS = CallSite::get(I);
// Not captured if the callee is readonly and doesn't return a copy
// through its return value.
if (CS.onlyReadsMemory() && I->getType() == Type::VoidTy)
break;
// Not captured if only passed via 'nocapture' arguments. Note that
// calling a function pointer does not in itself cause the pointer to
// be captured. This is a subtle point considering that (for example)
// the callee might return its own address. It is analogous to saying
// that loading a value from a pointer does not cause the pointer to be
// captured, even though the loaded value might be the pointer itself
// (think of self-referential objects).
CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
for (CallSite::arg_iterator A = B; A != E; ++A)
if (A->get() == V && !CS.paramHasAttr(A - B + 1, Attribute::NoCapture))
// The parameter is not marked 'nocapture' - captured.
return true;
// Only passed via 'nocapture' arguments, or is the called function - not
// captured.
break;
}
case Instruction::Free:
// Freeing a pointer does not cause it to be captured.
break;
case Instruction::Load:
// Loading from a pointer does not cause it to be captured.
break;
case Instruction::Store:
if (V == I->getOperand(0))
// Stored the pointer - it may be captured.
return true;
// Storing to the pointee does not cause the pointer to be captured.
break;
case Instruction::BitCast:
case Instruction::GetElementPtr:
case Instruction::PHI:
case Instruction::Select:
// The original value is not captured via this if the new value isn't.
for (Instruction::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE; ++UI) {
Use *U = &UI.getUse();
if (Visited.insert(U))
Worklist.push_back(U);
}
break;
default:
// Something else - be conservative and say it is captured.
return true;
}
}
// All uses examined - not captured.
return false;
}
/// AddNoCaptureAttrs - Deduce nocapture attributes for the SCC.
bool FunctionAttrs::AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC) {
bool Changed = false;
@@ -277,7 +198,7 @@ bool FunctionAttrs::AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC) {
for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A!=E; ++A)
if (isa<PointerType>(A->getType()) && !A->hasNoCaptureAttr() &&
!isCaptured(*F, A)) {
!PointerMayBeCaptured(A, true)) {
A->addAttr(Attribute::NoCapture);
++NumNoCapture;
Changed = true;