mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-11-11 08:07:22 +00:00
1df9859c40
and T->isPointerTy(). Convert most instances of the first form to the second form. Requested by Chris. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96344 91177308-0d34-0410-b5e6-96231b3b80d8
392 lines
13 KiB
C++
392 lines
13 KiB
C++
//===- FunctionAttrs.cpp - Pass which marks functions readnone or readonly ===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements a simple interprocedural pass which walks the
|
|
// call-graph, looking for functions which do not access or only read
|
|
// non-local memory, and marking them readnone/readonly. In addition,
|
|
// it marks function arguments (of pointer type) 'nocapture' if a call
|
|
// to the function does not create any copies of the pointer value that
|
|
// outlive the call. This more or less means that the pointer is only
|
|
// dereferenced, and not returned from the function or stored in a global.
|
|
// This pass is implemented as a bottom-up traversal of the call-graph.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "functionattrs"
|
|
#include "llvm/Transforms/IPO.h"
|
|
#include "llvm/CallGraphSCCPass.h"
|
|
#include "llvm/GlobalVariable.h"
|
|
#include "llvm/IntrinsicInst.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Analysis/CallGraph.h"
|
|
#include "llvm/Analysis/CaptureTracking.h"
|
|
#include "llvm/Analysis/MemoryBuiltins.h"
|
|
#include "llvm/ADT/SmallSet.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/ADT/UniqueVector.h"
|
|
#include "llvm/Support/InstIterator.h"
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumReadNone, "Number of functions marked readnone");
|
|
STATISTIC(NumReadOnly, "Number of functions marked readonly");
|
|
STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
|
|
STATISTIC(NumNoAlias, "Number of function returns marked noalias");
|
|
|
|
namespace {
|
|
struct FunctionAttrs : public CallGraphSCCPass {
|
|
static char ID; // Pass identification, replacement for typeid
|
|
FunctionAttrs() : CallGraphSCCPass(&ID) {}
|
|
|
|
// runOnSCC - Analyze the SCC, performing the transformation if possible.
|
|
bool runOnSCC(std::vector<CallGraphNode *> &SCC);
|
|
|
|
// AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
|
|
bool AddReadAttrs(const std::vector<CallGraphNode *> &SCC);
|
|
|
|
// AddNoCaptureAttrs - Deduce nocapture attributes for the SCC.
|
|
bool AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC);
|
|
|
|
// IsFunctionMallocLike - Does this function allocate new memory?
|
|
bool IsFunctionMallocLike(Function *F,
|
|
SmallPtrSet<Function*, 8> &) const;
|
|
|
|
// AddNoAliasAttrs - Deduce noalias attributes for the SCC.
|
|
bool AddNoAliasAttrs(const std::vector<CallGraphNode *> &SCC);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesCFG();
|
|
CallGraphSCCPass::getAnalysisUsage(AU);
|
|
}
|
|
|
|
bool PointsToLocalMemory(Value *V);
|
|
};
|
|
}
|
|
|
|
char FunctionAttrs::ID = 0;
|
|
static RegisterPass<FunctionAttrs>
|
|
X("functionattrs", "Deduce function attributes");
|
|
|
|
Pass *llvm::createFunctionAttrsPass() { return new FunctionAttrs(); }
|
|
|
|
|
|
/// PointsToLocalMemory - Returns whether the given pointer value points to
|
|
/// memory that is local to the function. Global constants are considered
|
|
/// local to all functions.
|
|
bool FunctionAttrs::PointsToLocalMemory(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 std::vector<CallGraphNode *> &SCC) {
|
|
SmallPtrSet<Function*, 8> SCCNodes;
|
|
|
|
// Fill SCCNodes with the elements of the SCC. Used for quickly
|
|
// looking up whether a given CallGraphNode is in this SCC.
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i)
|
|
SCCNodes.insert(SCC[i]->getFunction());
|
|
|
|
// Check if any of the functions in the SCC read or write memory. If they
|
|
// write memory then they can't be marked readnone or readonly.
|
|
bool ReadsMemory = false;
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
|
|
Function *F = SCC[i]->getFunction();
|
|
|
|
if (F == 0)
|
|
// External node - may write memory. Just give up.
|
|
return false;
|
|
|
|
if (F->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())
|
|
// May write memory. Just give up.
|
|
return false;
|
|
|
|
ReadsMemory = true;
|
|
continue;
|
|
}
|
|
|
|
// Scan the function body for instructions that may read or write memory.
|
|
for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
|
|
Instruction *I = &*II;
|
|
|
|
// 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 = CallSite::get(I);
|
|
if (CS.getInstruction() && CS.getCalledFunction()) {
|
|
// Ignore calls to functions in the same SCC.
|
|
if (SCCNodes.count(CS.getCalledFunction()))
|
|
continue;
|
|
// Ignore intrinsics that only access local memory.
|
|
if (unsigned id = CS.getCalledFunction()->getIntrinsicID())
|
|
if (AliasAnalysis::getModRefBehavior(id) ==
|
|
AliasAnalysis::AccessesArguments) {
|
|
// Check that all pointer arguments point to local memory.
|
|
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
|
|
CI != CE; ++CI) {
|
|
Value *Arg = *CI;
|
|
if (Arg->getType()->isPointerTy() && !PointsToLocalMemory(Arg))
|
|
// Writes memory. Just give up.
|
|
return false;
|
|
}
|
|
// Only reads and writes local memory.
|
|
continue;
|
|
}
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
// Ignore loads from local memory.
|
|
if (PointsToLocalMemory(LI->getPointerOperand()))
|
|
continue;
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
|
|
// Ignore stores to local memory.
|
|
if (PointsToLocalMemory(SI->getPointerOperand()))
|
|
continue;
|
|
}
|
|
|
|
// Any remaining instructions need to be taken seriously! Check if they
|
|
// read or write memory.
|
|
if (I->mayWriteToMemory())
|
|
// Writes memory. Just give up.
|
|
return false;
|
|
|
|
if (isMalloc(I))
|
|
// malloc claims not to write memory! PR3754.
|
|
return false;
|
|
|
|
// If this instruction may read memory, remember that.
|
|
ReadsMemory |= I->mayReadFromMemory();
|
|
}
|
|
}
|
|
|
|
// Success! Functions in this SCC do not access memory, or only read memory.
|
|
// Give them the appropriate attribute.
|
|
bool MadeChange = false;
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
|
|
Function *F = SCC[i]->getFunction();
|
|
|
|
if (F->doesNotAccessMemory())
|
|
// Already perfect!
|
|
continue;
|
|
|
|
if (F->onlyReadsMemory() && ReadsMemory)
|
|
// No change.
|
|
continue;
|
|
|
|
MadeChange = true;
|
|
|
|
// Clear out any existing attributes.
|
|
F->removeAttribute(~0, Attribute::ReadOnly | Attribute::ReadNone);
|
|
|
|
// Add in the new attribute.
|
|
F->addAttribute(~0, ReadsMemory? Attribute::ReadOnly : Attribute::ReadNone);
|
|
|
|
if (ReadsMemory)
|
|
++NumReadOnly;
|
|
else
|
|
++NumReadNone;
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// AddNoCaptureAttrs - Deduce nocapture attributes for the SCC.
|
|
bool FunctionAttrs::AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC) {
|
|
bool Changed = false;
|
|
|
|
// Check each function in turn, determining which pointer arguments are not
|
|
// captured.
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
|
|
Function *F = SCC[i]->getFunction();
|
|
|
|
if (F == 0)
|
|
// External node - skip it;
|
|
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())
|
|
continue;
|
|
|
|
for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A!=E; ++A)
|
|
if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr() &&
|
|
!PointerMayBeCaptured(A, true, /*StoreCaptures=*/false)) {
|
|
A->addAttr(Attribute::NoCapture);
|
|
++NumNoCapture;
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// IsFunctionMallocLike - A function is malloc-like if it returns either null
|
|
/// or a pointer that doesn't alias any other pointer visible to the caller.
|
|
bool FunctionAttrs::IsFunctionMallocLike(Function *F,
|
|
SmallPtrSet<Function*, 8> &SCCNodes) const {
|
|
UniqueVector<Value *> FlowsToReturn;
|
|
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
|
|
if (ReturnInst *Ret = dyn_cast<ReturnInst>(I->getTerminator()))
|
|
FlowsToReturn.insert(Ret->getReturnValue());
|
|
|
|
for (unsigned i = 0; i != FlowsToReturn.size(); ++i) {
|
|
Value *RetVal = FlowsToReturn[i+1]; // UniqueVector[0] is reserved.
|
|
|
|
if (Constant *C = dyn_cast<Constant>(RetVal)) {
|
|
if (!C->isNullValue() && !isa<UndefValue>(C))
|
|
return false;
|
|
|
|
continue;
|
|
}
|
|
|
|
if (isa<Argument>(RetVal))
|
|
return false;
|
|
|
|
if (Instruction *RVI = dyn_cast<Instruction>(RetVal))
|
|
switch (RVI->getOpcode()) {
|
|
// Extend the analysis by looking upwards.
|
|
case Instruction::BitCast:
|
|
case Instruction::GetElementPtr:
|
|
FlowsToReturn.insert(RVI->getOperand(0));
|
|
continue;
|
|
case Instruction::Select: {
|
|
SelectInst *SI = cast<SelectInst>(RVI);
|
|
FlowsToReturn.insert(SI->getTrueValue());
|
|
FlowsToReturn.insert(SI->getFalseValue());
|
|
continue;
|
|
}
|
|
case Instruction::PHI: {
|
|
PHINode *PN = cast<PHINode>(RVI);
|
|
for (int i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
FlowsToReturn.insert(PN->getIncomingValue(i));
|
|
continue;
|
|
}
|
|
|
|
// Check whether the pointer came from an allocation.
|
|
case Instruction::Alloca:
|
|
break;
|
|
case Instruction::Call:
|
|
case Instruction::Invoke: {
|
|
CallSite CS(RVI);
|
|
if (CS.paramHasAttr(0, Attribute::NoAlias))
|
|
break;
|
|
if (CS.getCalledFunction() &&
|
|
SCCNodes.count(CS.getCalledFunction()))
|
|
break;
|
|
} // fall-through
|
|
default:
|
|
return false; // Did not come from an allocation.
|
|
}
|
|
|
|
if (PointerMayBeCaptured(RetVal, false, /*StoreCaptures=*/false))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// AddNoAliasAttrs - Deduce noalias attributes for the SCC.
|
|
bool FunctionAttrs::AddNoAliasAttrs(const std::vector<CallGraphNode *> &SCC) {
|
|
SmallPtrSet<Function*, 8> SCCNodes;
|
|
|
|
// Fill SCCNodes with the elements of the SCC. Used for quickly
|
|
// looking up whether a given CallGraphNode is in this SCC.
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i)
|
|
SCCNodes.insert(SCC[i]->getFunction());
|
|
|
|
// Check each function in turn, determining which functions return noalias
|
|
// pointers.
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
|
|
Function *F = SCC[i]->getFunction();
|
|
|
|
if (F == 0)
|
|
// External node - skip it;
|
|
return false;
|
|
|
|
// Already noalias.
|
|
if (F->doesNotAlias(0))
|
|
continue;
|
|
|
|
// Definitions with weak linkage may be overridden at linktime, so
|
|
// treat them like declarations.
|
|
if (F->isDeclaration() || F->mayBeOverridden())
|
|
return false;
|
|
|
|
// We annotate noalias return values, which are only applicable to
|
|
// pointer types.
|
|
if (!F->getReturnType()->isPointerTy())
|
|
continue;
|
|
|
|
if (!IsFunctionMallocLike(F, SCCNodes))
|
|
return false;
|
|
}
|
|
|
|
bool MadeChange = false;
|
|
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
|
|
Function *F = SCC[i]->getFunction();
|
|
if (F->doesNotAlias(0) || !F->getReturnType()->isPointerTy())
|
|
continue;
|
|
|
|
F->setDoesNotAlias(0);
|
|
++NumNoAlias;
|
|
MadeChange = true;
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
bool FunctionAttrs::runOnSCC(std::vector<CallGraphNode *> &SCC) {
|
|
bool Changed = AddReadAttrs(SCC);
|
|
Changed |= AddNoCaptureAttrs(SCC);
|
|
Changed |= AddNoAliasAttrs(SCC);
|
|
return Changed;
|
|
}
|