BasicAliasAnalysis and FunctionAttrs were both
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
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index e29e914..4748573 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -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 @@
// 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 @@
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 @@
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;