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Revert r53606. It turns out that explicitely tracking the liveness of the

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return value as a whole in deadargelim is really not needed now that we simply
rebuild the old return value and actually prevents some canonicalization from
taking place.

This revert stops deadargelim from changing {i32} into i32 for now, but I'll
fix that next.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53609 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthijs Kooijman 2008-07-15 14:39:36 +00:00
parent eb32b453b3
commit d1d1de7f39
1 changed files with 103 additions and 97 deletions
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170
lib/Transforms/IPO/DeadArgumentElimination.cpp
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@ -47,14 +47,12 @@ namespace {
/// Struct that represents (part of) either a return value or a function /// Struct that represents (part of) either a return value or a function
/// argument. Used so that arguments and return values can be used /// argument. Used so that arguments and return values can be used
/// interchangably. Idx == -1 means the entire return value, while other /// interchangably.
/// indices mean the corresponding element in the struct return type (if
/// any).
struct RetOrArg { struct RetOrArg {
RetOrArg(const Function* F, signed Idx, bool IsArg) : F(F), Idx(Idx), RetOrArg(const Function* F, unsigned Idx, bool IsArg) : F(F), Idx(Idx),
IsArg(IsArg) {} IsArg(IsArg) {}
const Function *F; const Function *F;
signed Idx; unsigned Idx;
bool IsArg; bool IsArg;
/// Make RetOrArg comparable, so we can put it into a map. /// Make RetOrArg comparable, so we can put it into a map.
@ -73,10 +71,8 @@ namespace {
} }
std::string getDescription() const { std::string getDescription() const {
return std::string((!IsArg && Idx != -1 ? "partial " : "")) return std::string((IsArg ? "Argument #" : "Return value #"))
+ (IsArg ? "argument #" : "return value") + utostr(Idx) + " of function " + F->getName();
+ (!IsArg && Idx == -1 ? "" : " #" + utostr(Idx))
+ " of function " + F->getName();
} }
}; };
@ -88,11 +84,11 @@ namespace {
enum Liveness { Live, MaybeLive }; enum Liveness { Live, MaybeLive };
/// Convenience wrapper /// Convenience wrapper
RetOrArg CreateRet(const Function *F, signed Idx) { RetOrArg CreateRet(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, false); return RetOrArg(F, Idx, false);
} }
/// Convenience wrapper /// Convenience wrapper
RetOrArg CreateArg(const Function *F, signed Idx) { RetOrArg CreateArg(const Function *F, unsigned Idx) {
return RetOrArg(F, Idx, true); return RetOrArg(F, Idx, true);
} }
@ -133,7 +129,7 @@ namespace {
private: private:
Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses); Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses, Liveness SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
signed RetValNum = -1); unsigned RetValNum = 0);
Liveness SurveyUses(Value *V, UseVector &MaybeLiveUses); Liveness SurveyUses(Value *V, UseVector &MaybeLiveUses);
void SurveyFunction(Function &F); void SurveyFunction(Function &F);
@ -282,6 +278,18 @@ bool DAE::DeleteDeadVarargs(Function &Fn) {
return true; return true;
} }
/// Convenience function that returns the number of return values. It returns 0
/// for void functions and 1 for functions not returning a struct. It returns
/// the number of struct elements for functions returning a struct.
static unsigned NumRetVals(const Function *F) {
if (F->getReturnType() == Type::VoidTy)
return 0;
else if (const StructType *STy = dyn_cast<StructType>(F->getReturnType()))
return STy->getNumElements();
else
return 1;
}
/// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not /// MarkIfNotLive - This checks Use for liveness in LiveValues. If Use is not
/// live, it adds Use to the MaybeLiveUses argument. Returns the determined /// live, it adds Use to the MaybeLiveUses argument. Returns the determined
/// liveness of Use. /// liveness of Use.
@ -296,15 +304,16 @@ DAE::Liveness DAE::MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses) {
return MaybeLive; return MaybeLive;
} }
/// SurveyUse - This looks at a single use of an argument or return value /// SurveyUse - This looks at a single use of an argument or return value
/// and determines if it should be alive or not. Adds this use to MaybeLiveUses /// and determines if it should be alive or not. Adds this use to MaybeLiveUses
/// if it causes the used value to become MaybeAlive. /// if it causes the used value to become MaybeAlive.
/// ///
/// RetValNum is the return value number to use when this use is used in a /// RetValNum is the return value number to use when this use is used in a
/// return instruction. This is used in the recursion, you should always leave /// return instruction. This is used in the recursion, you should always leave
/// it at -1. /// it at 0.
DAE::Liveness DAE::SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses, DAE::Liveness DAE::SurveyUse(Value::use_iterator U, UseVector &MaybeLiveUses,
signed RetValNum) { unsigned RetValNum) {
Value *V = *U; Value *V = *U;
if (ReturnInst *RI = dyn_cast<ReturnInst>(V)) { if (ReturnInst *RI = dyn_cast<ReturnInst>(V)) {
// The value is returned from a function. It's only live when the // The value is returned from a function. It's only live when the
@ -393,23 +402,16 @@ DAE::Liveness DAE::SurveyUses(Value *V, UseVector &MaybeLiveUses) {
// well as arguments to functions which have their "address taken". // well as arguments to functions which have their "address taken".
// //
void DAE::SurveyFunction(Function &F) { void DAE::SurveyFunction(Function &F) {
const StructType *STy = dyn_cast<StructType>(F.getFunctionType()->getReturnType()); unsigned RetCount = NumRetVals(&F);
// Store the number of partial return values, which we only have if the return
// type is a struct.
unsigned PartialRetVals = (STy ? STy->getNumElements() : 0);
// Assume all return values are dead // Assume all return values are dead
typedef SmallVector<Liveness, 5> RetVals; typedef SmallVector<Liveness, 5> RetVals;
// Allocate one slot for the entire return value (index 0) and one for each RetVals RetValLiveness(RetCount, MaybeLive);
// partial return value.
RetVals RetValLiveness(PartialRetVals + 1, MaybeLive);
typedef SmallVector<UseVector, 5> RetUses; typedef SmallVector<UseVector, 5> RetUses;
// These vectors map each return value to the uses that make it MaybeLive, so // These vectors map each return value to the uses that make it MaybeLive, so
// we can add those to the Uses map if the return value really turns out to be // we can add those to the Uses map if the return value really turns out to be
// MaybeLive. // MaybeLive. Initialized to a list of RetCount empty lists.
// Allocate one slot for the entire return value (index 0) and one for each RetUses MaybeLiveRetUses(RetCount);
// partial return value.
RetUses MaybeLiveRetUses(PartialRetVals + 1);
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
@ -426,6 +428,10 @@ void DAE::SurveyFunction(Function &F) {
} }
DOUT << "DAE - Inspecting callers for fn: " << F.getName() << "\n"; DOUT << "DAE - Inspecting callers for fn: " << F.getName() << "\n";
// Keep track of the number of live retvals, so we can skip checks once all
// of them turn out to be live.
unsigned NumLiveRetVals = 0;
const Type *STy = dyn_cast<StructType>(F.getReturnType());
// Loop all uses of the function. // Loop all uses of the function.
for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) { for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I) {
// If the function is PASSED IN as an argument, its address has been // If the function is PASSED IN as an argument, its address has been
@ -446,8 +452,9 @@ void DAE::SurveyFunction(Function &F) {
// If we end up here, we are looking at a direct call to our function. // If we end up here, we are looking at a direct call to our function.
// Now, check how our return value(s) is/are used in this caller. Don't // Now, check how our return value(s) is/are used in this caller. Don't
// bother checking return values if the entire value is live already. // bother checking return values if all of them are live already.
if (RetValLiveness[0] != Live) { if (NumLiveRetVals != RetCount) {
if (STy) {
// Check all uses of the return value. // Check all uses of the return value.
for (Value::use_iterator I = TheCall->use_begin(), for (Value::use_iterator I = TheCall->use_begin(),
E = TheCall->use_end(); I != E; ++I) { E = TheCall->use_end(); I != E; ++I) {
@ -456,32 +463,32 @@ void DAE::SurveyFunction(Function &F) {
// This use uses a part of our return value, survey the uses of // This use uses a part of our return value, survey the uses of
// that part and store the results for this index only. // that part and store the results for this index only.
unsigned Idx = *Ext->idx_begin(); unsigned Idx = *Ext->idx_begin();
// + 1 to skip the "entire retval" index (0) if (RetValLiveness[Idx] != Live) {
Liveness &IsLive = RetValLiveness[Idx + 1]; RetValLiveness[Idx] = SurveyUses(Ext, MaybeLiveRetUses[Idx]);
if (IsLive != Live) { if (RetValLiveness[Idx] == Live)
// Don't bother checking if this retval was already live NumLiveRetVals++;
// Survey all uses of the extractvalue
// + 1 to skip the "entire retval" index (0)
IsLive = SurveyUses(Ext, MaybeLiveRetUses[Idx + 1]);
} }
} else { } else {
// Survey this use // Used by something else than extractvalue. Mark all return
RetValLiveness[0] = SurveyUse(I, MaybeLiveRetUses[0]); // values as live.
if (RetValLiveness[0] == Live) for (unsigned i = 0; i != RetCount; ++i )
RetValLiveness[i] = Live;
NumLiveRetVals = RetCount;
break; break;
} }
} }
} else {
// Single return value
RetValLiveness[0] = SurveyUses(TheCall, MaybeLiveRetUses[0]);
if (RetValLiveness[0] == Live)
NumLiveRetVals = RetCount;
}
} }
} }
// Now we've inspected all callers, record the liveness of our return values. // Now we've inspected all callers, record the liveness of our return values.
MarkValue(CreateRet(&F, -1), RetValLiveness[0], MaybeLiveRetUses[0]); for (unsigned i = 0; i != RetCount; ++i)
if (RetValLiveness[0] != Live) MarkValue(CreateRet(&F, i), RetValLiveness[i], MaybeLiveRetUses[i]);
// If the entire retval (0) is Live, MarkValue will have marked all other retvals live
// as well, so we can skip this.
for (unsigned i = 0; i != PartialRetVals; ++i)
// + 1 to skip the "entire retval" index (0)
MarkValue(CreateRet(&F, i), RetValLiveness[i + 1], MaybeLiveRetUses[i + 1]);
DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n"; DOUT << "DAE - Inspecting args for fn: " << F.getName() << "\n";
@ -532,11 +539,8 @@ void DAE::MarkLive(const Function &F) {
for (unsigned i = 0, e = F.arg_size(); i != e; ++i) for (unsigned i = 0, e = F.arg_size(); i != e; ++i)
PropagateLiveness(CreateArg(&F, i)); PropagateLiveness(CreateArg(&F, i));
// Mark all return values as live. // Mark all return values as live.
const Type *RTy = F.getFunctionType()->getReturnType(); for (unsigned i = 0, e = NumRetVals(&F); i != e; ++i)
if (const StructType *STy = dyn_cast<StructType>(RTy))
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
PropagateLiveness(CreateRet(&F, i)); PropagateLiveness(CreateRet(&F, i));
PropagateLiveness(CreateRet(&F, -1));
} }
/// MarkLive - Mark the given return value or argument as live. Additionally, /// MarkLive - Mark the given return value or argument as live. Additionally,
@ -551,16 +555,6 @@ void DAE::MarkLive(const RetOrArg &RA) {
DOUT << "DAE - Marking " << RA.getDescription() << " live\n"; DOUT << "DAE - Marking " << RA.getDescription() << " live\n";
PropagateLiveness(RA); PropagateLiveness(RA);
if (!RA.IsArg && RA.Idx == -1) {
// Entire return value live?
const Type *RTy = RA.F->getFunctionType()->getReturnType();
if (const StructType *STy = dyn_cast<StructType>(RTy))
// And the function returns a struct?
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
// Mark all partial return values live as well then
MarkLive(CreateRet(RA.F, i));
}
} }
/// PropagateLiveness - Given that RA is a live value, propagate it's liveness /// PropagateLiveness - Given that RA is a live value, propagate it's liveness
@ -605,20 +599,20 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
// Find out the new return value. // Find out the new return value.
const Type *RetTy = FTy->getReturnType(); const Type *RetTy = FTy->getReturnType();
const StructType *STy = dyn_cast<StructType>(RetTy);
const unsigned PartialRetVals = (STy ? STy->getNumElements() : 0);
const Type *NRetTy = NULL; const Type *NRetTy = NULL;
// -1 means unused, other numbers are the new index. Initialized to -1 for unsigned RetCount = NumRetVals(F);
// every partial return value we have. // Explicitly track if anything changed, for debugging.
SmallVector<int, 5> NewRetIdxs(PartialRetVals, -1); bool Changed = false;
// -1 means unused, other numbers are the new index
SmallVector<int, 5> NewRetIdxs(RetCount, -1);
std::vector<const Type*> RetTypes; std::vector<const Type*> RetTypes;
if (LiveValues.count(CreateRet(F, -1))) { if (RetTy == Type::VoidTy) {
// If the entire return value is live, leave it unchanged. NRetTy = Type::VoidTy;
NRetTy = RetTy;
} else { } else {
if (STy) { const StructType *STy = dyn_cast<StructType>(RetTy);
// Look at each of the partial return values individually. if (STy)
for (unsigned i = 0; i != PartialRetVals; ++i) { // Look at each of the original return values individually.
for (unsigned i = 0; i != RetCount; ++i) {
RetOrArg Ret = CreateRet(F, i); RetOrArg Ret = CreateRet(F, i);
if (LiveValues.erase(Ret)) { if (LiveValues.erase(Ret)) {
RetTypes.push_back(STy->getElementType(i)); RetTypes.push_back(STy->getElementType(i));
@ -627,20 +621,25 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
++NumRetValsEliminated; ++NumRetValsEliminated;
DOUT << "DAE - Removing return value " << i << " from " DOUT << "DAE - Removing return value " << i << " from "
<< F->getNameStart() << "\n"; << F->getNameStart() << "\n";
// We remove the value by not adding anything to RetTypes. Changed = true;
} }
} }
} else if (RetTy != Type::VoidTy) { else
// We used to return a single value, which is now dead (already checked in // We used to return a single value.
// the if above) if (LiveValues.erase(CreateRet(F, 0))) {
RetTypes.push_back(RetTy);
NewRetIdxs[0] = 0;
} else {
DOUT << "DAE - Removing return value from " << F->getNameStart() DOUT << "DAE - Removing return value from " << F->getNameStart()
<< "\n"; << "\n";
++NumRetValsEliminated; ++NumRetValsEliminated;
// We remove the value by not adding anything to RetTypes. Changed = true;
} }
if (RetTypes.size() > 1 || (STy && STy->getNumElements()==RetTypes.size()))
if (RetTypes.size() > 1) // More than one return type? Return a struct with them. Also, if we used
// More than one return type? Return a struct with them. // to return a struct and didn't change the number of return values,
// return a struct again. This prevents changing {something} into
// something and {} into void.
// Make the new struct packed if we used to return a packed struct // Make the new struct packed if we used to return a packed struct
// already. // already.
NRetTy = StructType::get(RetTypes, STy->isPacked()); NRetTy = StructType::get(RetTypes, STy->isPacked());
@ -649,7 +648,7 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
// return a struct with that simple value before. // return a struct with that simple value before.
NRetTy = RetTypes.front(); NRetTy = RetTypes.front();
else if (RetTypes.size() == 0) else if (RetTypes.size() == 0)
// No return types? Make it void. // No return types? Make it void, but only if we didn't use to return {}.
NRetTy = Type::VoidTy; NRetTy = Type::VoidTy;
} }
@ -689,6 +688,7 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
++NumArgumentsEliminated; ++NumArgumentsEliminated;
DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart() DOUT << "DAE - Removing argument " << i << " (" << I->getNameStart()
<< ") from " << F->getNameStart() << "\n"; << ") from " << F->getNameStart() << "\n";
Changed = true;
} }
} }
@ -714,6 +714,11 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
if (NFTy == FTy) if (NFTy == FTy)
return false; return false;
// The function type is only allowed to be different if we actually left out
// an argument or return value.
assert(Changed && "Function type changed while no arguments or return values"
"were removed!");
// Create the new function body and insert it into the module... // Create the new function body and insert it into the module...
Function *NF = Function::Create(NFTy, F->getLinkage()); Function *NF = Function::Create(NFTy, F->getLinkage());
NF->copyAttributesFrom(F); NF->copyAttributesFrom(F);
@ -794,15 +799,16 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
// Replace by null for now. // Replace by null for now.
Call->replaceAllUsesWith(Constant::getNullValue(Call->getType())); Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
} else { } else {
assert(STy && "Return type changed, but not into a void. The old " assert(isa<StructType>(RetTy) && "Return type changed, but not into a"
"return type must have been a struct!"); "void. The old return type must have"
"been a struct!");
// We used to return a struct. Instead of doing smart stuff with all the // We used to return a struct. Instead of doing smart stuff with all the
// uses of this struct, we will just rebuild it using // uses of this struct, we will just rebuild it using
// extract/insertvalue chaining and let instcombine clean that up. // extract/insertvalue chaining and let instcombine clean that up.
// //
// Start out building up our return value from undef // Start out building up our return value from undef
Value *RetVal = llvm::UndefValue::get(RetTy); Value *RetVal = llvm::UndefValue::get(RetTy);
for (unsigned i = 0; i != PartialRetVals; ++i) for (unsigned i = 0; i != RetCount; ++i)
if (NewRetIdxs[i] != -1) { if (NewRetIdxs[i] != -1) {
Value *V; Value *V;
if (RetTypes.size() > 1) if (RetTypes.size() > 1)
@ -868,7 +874,7 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
Value *OldRet = RI->getOperand(0); Value *OldRet = RI->getOperand(0);
// Start out building up our return value from undef // Start out building up our return value from undef
RetVal = llvm::UndefValue::get(NRetTy); RetVal = llvm::UndefValue::get(NRetTy);
for (unsigned i = 0; i != PartialRetVals; ++i) for (unsigned i = 0; i != RetCount; ++i)
if (NewRetIdxs[i] != -1) { if (NewRetIdxs[i] != -1) {
ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i, ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i,
"oldret", RI); "oldret", RI);