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[GMR] Wrap all of the per-function information behind a more strongly 

typed interface as a precursor to rewriting how it is stored.

This way we know that the access paths are controlled and it should be
easy to store these bits in a different way.

No functionality changed.

llvm-svn: 242974
This commit is contained in:
Chandler Carruth 2015-07-22 23:56:31 +00:00
parent 0106479fa8
commit 5657b73ebe
1 changed files with 91 additions and 62 deletions
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153
llvm/lib/Analysis/IPA/GlobalsModRef.cpp
View File

@ -57,33 +57,61 @@ static cl::opt<bool> EnableUnsafeGlobalsModRefAliasResults(
"enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden);
namespace {
/// FunctionRecord - One instance of this structure is stored for every
/// function in the program. Later, the entries for these functions are
/// removed if the function is found to call an external function (in which
/// case we know nothing about it.
struct FunctionRecord {
/// GlobalInfo - Maintain mod/ref info for all of the globals without
/// addresses taken that are read or written (transitively) by this
/// function.
std::map<const GlobalValue *, unsigned> GlobalInfo;
/// The mod/ref information collected for a particular function.
///
/// We collect information about mod/ref behavior of a function here, both in
/// general and as pertains to specific globals. We only have this detailed
/// information when we know *something* useful about the behavior. If we
/// saturate to fully general mod/ref, we remove the info for the function.
class FunctionInfo {
public:
FunctionInfo() : MayReadAnyGlobal(false), MRI(MRI_NoModRef) {}
/// MayReadAnyGlobal - May read global variables, but it is not known which.
bool MayReadAnyGlobal;
/// Returns the \c ModRefInfo info for this function.
ModRefInfo getModRefInfo() const { return MRI; }
unsigned getInfoForGlobal(const GlobalValue *GV) const {
unsigned Effect = MayReadAnyGlobal ? MRI_Ref : 0;
std::map<const GlobalValue *, unsigned>::const_iterator I =
GlobalInfo.find(GV);
/// Adds new \c ModRefInfo for this function to its state.
void addModRefInfo(ModRefInfo NewMRI) { MRI = ModRefInfo(MRI | NewMRI); }
/// Returns whether this function may read any global variable, and we don't
/// know which global.
bool mayReadAnyGlobal() const { return MayReadAnyGlobal; }
/// Sets this function as potentially reading from any global.
void setMayReadAnyGlobal() { MayReadAnyGlobal = true; }
/// Returns the \c ModRefInfo info for this function w.r.t. a particular
/// global, which may be more precise than the general information above.
ModRefInfo getModRefInfoForGlobal(const GlobalValue &GV) const {
ModRefInfo GlobalMRI = MayReadAnyGlobal ? MRI_Ref : MRI_NoModRef;
auto I = GlobalInfo.find(&GV);
if (I != GlobalInfo.end())
Effect |= I->second;
return Effect;
GlobalMRI = ModRefInfo(GlobalMRI | I->second);
return GlobalMRI;
}
/// FunctionEffect - Capture whether or not this function reads or writes to
/// ANY memory. If not, we can do a lot of aggressive analysis on it.
unsigned FunctionEffect;
/// Access the entire map of mod/ref info for specific globals.
const std::map<const GlobalValue *, ModRefInfo> &getGlobalModRefInfo() const {
return GlobalInfo;
}
FunctionRecord() : MayReadAnyGlobal(false), FunctionEffect(0) {}
void addModRefInfoForGlobal(const GlobalValue &GV, ModRefInfo NewMRI) {
auto &GlobalMRI = GlobalInfo[&GV];
GlobalMRI = ModRefInfo(GlobalMRI | NewMRI);
}
private:
/// Maintain mod/ref info for all of the globals without addresses taken that
/// are read or written (transitively) by this function.
std::map<const GlobalValue *, ModRefInfo> GlobalInfo;
/// Flag indicating this function read global variables, but it is not known
/// which.
bool MayReadAnyGlobal;
/// Captures whether or not this function reads or writes to ANY memory. If
/// not, we can do a lot of aggressive analysis on it.
ModRefInfo MRI;
};
/// GlobalsModRef - The actual analysis pass.
@ -99,9 +127,8 @@ class GlobalsModRef : public ModulePass, public AliasAnalysis {
/// indirect global, this map indicates which one.
DenseMap<const Value *, const GlobalValue *> AllocsForIndirectGlobals;
/// FunctionInfo - For each function, keep track of what globals are
/// modified or read.
DenseMap<const Function *, FunctionRecord> FunctionInfo;
/// For each function, keep track of what globals are modified or read.
DenseMap<const Function *, FunctionInfo> FunctionInfos;
/// Handle to clear this analysis on deletion of values.
struct DeletionCallbackHandle final : CallbackVH {
@ -196,10 +223,10 @@ public:
FunctionModRefBehavior getModRefBehavior(const Function *F) override {
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
if (FunctionRecord *FR = getFunctionInfo(F)) {
if (FR->FunctionEffect == 0)
if (FunctionInfo *FI = getFunctionInfo(F)) {
if (FI->getModRefInfo() == MRI_NoModRef)
Min = FMRB_DoesNotAccessMemory;
else if ((FR->FunctionEffect & MRI_Mod) == 0)
else if ((FI->getModRefInfo() & MRI_Mod) == 0)
Min = FMRB_OnlyReadsMemory;
}
@ -213,10 +240,10 @@ public:
FunctionModRefBehavior Min = FMRB_UnknownModRefBehavior;
if (const Function *F = CS.getCalledFunction())
if (FunctionRecord *FR = getFunctionInfo(F)) {
if (FR->FunctionEffect == 0)
if (FunctionInfo *FI = getFunctionInfo(F)) {
if (FI->getModRefInfo() == MRI_NoModRef)
Min = FMRB_DoesNotAccessMemory;
else if ((FR->FunctionEffect & MRI_Mod) == 0)
else if ((FI->getModRefInfo() & MRI_Mod) == 0)
Min = FMRB_OnlyReadsMemory;
}
@ -224,11 +251,11 @@ public:
}
private:
/// getFunctionInfo - Return the function info for the function, or null if
/// we don't have anything useful to say about it.
FunctionRecord *getFunctionInfo(const Function *F) {
auto I = FunctionInfo.find(F);
if (I != FunctionInfo.end())
/// Returns the function info for the function, or null if we don't have
/// anything useful to say about it.
FunctionInfo *getFunctionInfo(const Function *F) {
auto I = FunctionInfos.find(F);
if (I != FunctionInfos.end())
return &I->second;
return nullptr;
}
@ -280,11 +307,11 @@ void GlobalsModRef::AnalyzeGlobals(Module &M) {
Handles.front().I = Handles.begin();
for (Function *Reader : Readers)
FunctionInfo[Reader].GlobalInfo[&GV] |= MRI_Ref;
FunctionInfos[Reader].addModRefInfoForGlobal(GV, MRI_Ref);
if (!GV.isConstant()) // No need to keep track of writers to constants
for (Function *Writer : Writers)
FunctionInfo[Writer].GlobalInfo[&GV] |= MRI_Mod;
FunctionInfos[Writer].addModRefInfoForGlobal(GV, MRI_Mod);
++NumNonAddrTakenGlobalVars;
// If this global holds a pointer type, see if it is an indirect global.
@ -432,14 +459,14 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
// Calls externally - can't say anything useful. Remove any existing
// function records (may have been created when scanning globals).
for (auto *Node : SCC)
FunctionInfo.erase(Node->getFunction());
FunctionInfos.erase(Node->getFunction());
continue;
}
FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
FunctionInfo &FI = FunctionInfos[SCC[0]->getFunction()];
bool KnowNothing = false;
unsigned FunctionEffect = 0;
unsigned FunctionMRI = 0;
// Collect the mod/ref properties due to called functions. We only compute
// one mod-ref set.
@ -455,13 +482,13 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
if (F->doesNotAccessMemory()) {
// Can't do better than that!
} else if (F->onlyReadsMemory()) {
FunctionEffect |= MRI_Ref;
FunctionMRI |= MRI_Ref;
if (!F->isIntrinsic())
// This function might call back into the module and read a global -
// consider every global as possibly being read by this function.
FR.MayReadAnyGlobal = true;
FI.setMayReadAnyGlobal();
} else {
FunctionEffect |= MRI_ModRef;
FunctionMRI |= MRI_ModRef;
// Can't say anything useful unless it's an intrinsic - they don't
// read or write global variables of the kind considered here.
KnowNothing = !F->isIntrinsic();
@ -472,14 +499,16 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
CI != E && !KnowNothing; ++CI)
if (Function *Callee = CI->second->getFunction()) {
if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) {
if (FunctionInfo *CalleeFI = getFunctionInfo(Callee)) {
// Propagate function effect up.
FunctionEffect |= CalleeFR->FunctionEffect;
FunctionMRI |= CalleeFI->getModRefInfo();
// Incorporate callee's effects on globals into our info.
for (const auto &G : CalleeFR->GlobalInfo)
FR.GlobalInfo[G.first] |= G.second;
FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal;
for (const auto &G : CalleeFI->getGlobalModRefInfo())
FI.addModRefInfoForGlobal(*G.first, G.second);
if (CalleeFI->mayReadAnyGlobal())
FI.setMayReadAnyGlobal();
} else {
// Can't say anything about it. However, if it is inside our SCC,
// then nothing needs to be done.
@ -493,19 +522,19 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
}
// If we can't say anything useful about this SCC, remove all SCC functions
// from the FunctionInfo map.
// from the FunctionInfos map.
if (KnowNothing) {
for (auto *Node : SCC)
FunctionInfo.erase(Node->getFunction());
FunctionInfos.erase(Node->getFunction());
continue;
}
// Scan the function bodies for explicit loads or stores.
for (auto *Node : SCC) {
if (FunctionEffect == MRI_ModRef)
if (FunctionMRI == MRI_ModRef)
break; // The mod/ref lattice saturates here.
for (Instruction &I : inst_range(Node->getFunction())) {
if (FunctionEffect == MRI_ModRef)
if (FunctionMRI == MRI_ModRef)
break; // The mod/ref lattice saturates here.
// We handle calls specially because the graph-relevant aspects are
@ -514,13 +543,13 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
if (isAllocationFn(&I, TLI) || isFreeCall(&I, TLI)) {
// FIXME: It is completely unclear why this is necessary and not
// handled by the above graph code.
FunctionEffect |= MRI_ModRef;
FunctionMRI |= MRI_ModRef;
} else if (Function *Callee = CS.getCalledFunction()) {
// The callgraph doesn't include intrinsic calls.
if (Callee->isIntrinsic()) {
FunctionModRefBehavior Behaviour =
AliasAnalysis::getModRefBehavior(Callee);
FunctionEffect |= (Behaviour & MRI_ModRef);
FunctionMRI |= (Behaviour & MRI_ModRef);
}
}
continue;
@ -529,22 +558,22 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
// All non-call instructions we use the primary predicates for whether
// thay read or write memory.
if (I.mayReadFromMemory())
FunctionEffect |= MRI_Ref;
FunctionMRI |= MRI_Ref;
if (I.mayWriteToMemory())
FunctionEffect |= MRI_Mod;
FunctionMRI |= MRI_Mod;
}
}
if ((FunctionEffect & MRI_Mod) == 0)
if ((FunctionMRI & MRI_Mod) == 0)
++NumReadMemFunctions;
if (FunctionEffect == 0)
if (FunctionMRI == MRI_NoModRef)
++NumNoMemFunctions;
FR.FunctionEffect = FunctionEffect;
FI.addModRefInfo(ModRefInfo(FunctionMRI));
// Finally, now that we know the full effect on this SCC, clone the
// information to each function in the SCC.
for (unsigned i = 1, e = SCC.size(); i != e; ++i)
FunctionInfo[SCC[i]->getFunction()] = FR;
FunctionInfos[SCC[i]->getFunction()] = FI;
}
}
@ -633,8 +662,8 @@ ModRefInfo GlobalsModRef::getModRefInfo(ImmutableCallSite CS,
if (GV->hasLocalLinkage())
if (const Function *F = CS.getCalledFunction())
if (NonAddressTakenGlobals.count(GV))
if (const FunctionRecord *FR = getFunctionInfo(F))
Known = FR->getInfoForGlobal(GV);
if (const FunctionInfo *FI = getFunctionInfo(F))
Known = FI->getModRefInfoForGlobal(*GV);
if (Known == MRI_NoModRef)
return MRI_NoModRef; // No need to query other mod/ref analyses