[llvm-commits] [llvm] r62461 - in /llvm/trunk: include/llvm/Analysis/CaptureTracking.h lib/Analysis/BasicAliasAnalysis.cpp lib/Analysis/CaptureTracking.cpp lib/Transforms/IPO/FunctionAttrs.cpp
Duncan Sands
baldrick at free.fr
Sun Jan 18 04:19:34 PST 2009
Author: baldrick
Date: Sun Jan 18 06:19:30 2009
New Revision: 62461
URL: http://llvm.org/viewvc/llvm-project?rev=62461&view=rev
Log:
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
Added:
llvm/trunk/include/llvm/Analysis/CaptureTracking.h
llvm/trunk/lib/Analysis/CaptureTracking.cpp
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
Added: llvm/trunk/include/llvm/Analysis/CaptureTracking.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/CaptureTracking.h?rev=62461&view=auto
==============================================================================
--- llvm/trunk/include/llvm/Analysis/CaptureTracking.h (added)
+++ llvm/trunk/include/llvm/Analysis/CaptureTracking.h Sun Jan 18 06:19:30 2009
@@ -0,0 +1,29 @@
+//===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains routines that help determine which pointers are captured.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
+#define LLVM_ANALYSIS_CAPTURETRACKING_H
+
+namespace llvm {
+ class Value;
+
+ /// PointerMayBeCaptured - Return true if this pointer value may be captured
+ /// by the enclosing function (which is required to exist). This routine can
+ /// be expensive, so consider caching the results. The boolean ReturnCaptures
+ /// specifies whether returning the value (or part of it) from the function
+ /// counts as capturing it or not.
+ bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures);
+
+} // end namespace llvm
+
+#endif
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=62461&r1=62460&r2=62461&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Sun Jan 18 06:19:30 2009
@@ -14,6 +14,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
@@ -35,56 +36,6 @@
// Useful predicates
//===----------------------------------------------------------------------===//
-// Determine if a value escapes from the function it is contained in (being
-// returned by the function does not count as escaping here). If a value local
-// to the function does not escape, there is no way another function can mod/ref
-// it. We do this by looking at its uses and determining if they can escape
-// (recursively).
-static bool AddressMightEscape(const Value *V) {
- for (Value::use_const_iterator UI = V->use_begin(), E = V->use_end();
- UI != E; ++UI) {
- const Instruction *I = cast<Instruction>(*UI);
- switch (I->getOpcode()) {
- case Instruction::Load:
- break; //next use.
- case Instruction::Store:
- if (I->getOperand(0) == V)
- return true; // Escapes if the pointer is stored.
- break; // next use.
- case Instruction::GetElementPtr:
- if (AddressMightEscape(I))
- return true;
- break; // next use.
- case Instruction::BitCast:
- if (AddressMightEscape(I))
- return true;
- break; // next use
- case Instruction::Ret:
- // If returned, the address will escape to calling functions, but no
- // callees could modify it.
- break; // next use
- case Instruction::Call:
- // If the argument to the call has the nocapture attribute, then the call
- // may store or load to the pointer, but it cannot escape.
- if (cast<CallInst>(I)->paramHasAttr(UI.getOperandNo(),
- Attribute::NoCapture))
- continue;
- return true;
- case Instruction::Invoke:
- // If the argument to the call has the nocapture attribute, then the call
- // may store or load to the pointer, but it cannot escape.
- // Do compensate for the two BB operands, i.e. Arg1 is at index 3!
- if (cast<InvokeInst>(I)->paramHasAttr(UI.getOperandNo()-2,
- Attribute::NoCapture))
- continue;
- return true;
- default:
- return true;
- }
- }
- return false;
-}
-
static const User *isGEP(const Value *V) {
if (isa<GetElementPtrInst>(V) ||
(isa<ConstantExpr>(V) &&
@@ -158,7 +109,7 @@
static bool isNonEscapingLocalObject(const Value *V) {
// If this is a local allocation, check to see if it escapes.
if (isa<AllocationInst>(V) || isNoAliasCall(V))
- return !AddressMightEscape(V);
+ return !PointerMayBeCaptured(V, false);
// If this is an argument that corresponds to a byval or noalias argument,
// then it has not escaped before entering the function. Check if it escapes
@@ -168,7 +119,7 @@
// Don't bother analyzing arguments already known not to escape.
if (A->hasNoCaptureAttr())
return true;
- return !AddressMightEscape(V);
+ return !PointerMayBeCaptured(V, false);
}
return false;
}
Added: llvm/trunk/lib/Analysis/CaptureTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CaptureTracking.cpp?rev=62461&view=auto
==============================================================================
--- llvm/trunk/lib/Analysis/CaptureTracking.cpp (added)
+++ llvm/trunk/lib/Analysis/CaptureTracking.cpp Sun Jan 18 06:19:30 2009
@@ -0,0 +1,110 @@
+//===--- CaptureTracking.cpp - Determine whether a pointer is captured ----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains routines that help determine which pointers are captured.
+// A pointer value is captured if the function makes a copy of any part of the
+// pointer that outlives the call. Not being captured means, more or less, that
+// the pointer is only dereferenced and not stored in a global. Returning part
+// of the pointer as the function return value may or may not count as capturing
+// the pointer, depending on the context.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Instructions.h"
+#include "llvm/Value.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/CallSite.h"
+using namespace llvm;
+
+/// PointerMayBeCaptured - Return true if this pointer value may be captured
+/// by the enclosing function (which is required to exist). This routine can
+/// be expensive, so consider caching the results. The boolean ReturnCaptures
+/// specifies whether returning the value (or part of it) from the function
+/// counts as capturing it or not.
+bool llvm::PointerMayBeCaptured(const Value *V, bool ReturnCaptures) {
+ assert(isa<PointerType>(V->getType()) && "Capture is for pointers only!");
+ SmallVector<Use*, 16> Worklist;
+ SmallSet<Use*, 16> Visited;
+
+ for (Value::use_const_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::Ret:
+ if (ReturnCaptures)
+ return true;
+ 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;
+}
Modified: llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp?rev=62461&r1=62460&r2=62461&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/FunctionAttrs.cpp Sun Jan 18 06:19:30 2009
@@ -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;
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