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reimplement multiple return value handling in IPSCCP, making it

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more aggressive an correct.  This survives building llvm in 64-bit
mode with optimizations and the built llvm passes make check.

llvm-svn: 85973
This commit is contained in:
Chris Lattner 2009-11-03 23:40:48 +00:00
parent b50510c510
commit b634c6cdb5
2 changed files with 205 additions and 126 deletions
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328
lib/Transforms/Scalar/SCCP.cpp
View File

@ -159,6 +159,11 @@ class SCCPSolver : public InstVisitor<SCCPSolver> {
SmallPtrSet<BasicBlock*, 8> BBExecutable;// The BBs that are executable.
DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
/// StructValueState - This maintains ValueState for values that have
/// StructType, for example for formal arguments, calls, insertelement, etc.
///
DenseMap<std::pair<Value*, unsigned>, LatticeVal> StructValueState;
/// GlobalValue - If we are tracking any values for the contents of a global
/// variable, we keep a mapping from the constant accessor to the element of
/// the global, to the currently known value. If the value becomes
@ -173,6 +178,10 @@ class SCCPSolver : public InstVisitor<SCCPSolver> {
/// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
/// that return multiple values.
DenseMap<std::pair<Function*, unsigned>, LatticeVal> TrackedMultipleRetVals;
/// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
/// represented here for efficient lookup.
SmallPtrSet<Function*, 16> MRVFunctionsTracked;
/// TrackingIncomingArguments - This is the set of functions for whose
/// arguments we make optimistic assumptions about and try to prove as
@ -219,8 +228,8 @@ public:
/// specified global variable if it can. This is only legal to call if
/// performing Interprocedural SCCP.
void TrackValueOfGlobalVariable(GlobalVariable *GV) {
const Type *ElTy = GV->getType()->getElementType();
if (ElTy->isFirstClassType()) {
// We only track the contents of scalar globals.
if (GV->getType()->getElementType()->isSingleValueType()) {
LatticeVal &IV = TrackedGlobals[GV];
if (!isa<UndefValue>(GV->getInitializer()))
IV.markConstant(GV->getInitializer());
@ -233,6 +242,7 @@ public:
void AddTrackedFunction(Function *F) {
// Add an entry, F -> undef.
if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
MRVFunctionsTracked.insert(F);
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
LatticeVal()));
@ -264,6 +274,13 @@ public:
assert(I != ValueState.end() && "V is not in valuemap!");
return I->second;
}
LatticeVal getStructLatticeValueFor(Value *V, unsigned i) const {
DenseMap<std::pair<Value*, unsigned>, LatticeVal>::const_iterator I =
StructValueState.find(std::make_pair(V, i));
assert(I != StructValueState.end() && "V is not in valuemap!");
return I->second;
}
/// getTrackedRetVals - Get the inferred return value map.
///
@ -278,9 +295,20 @@ public:
}
void markOverdefined(Value *V) {
assert(!isa<StructType>(V->getType()) && "Should use other method");
markOverdefined(ValueState[V], V);
}
/// markAnythingOverdefined - Mark the specified value overdefined. This
/// works with both scalars and structs.
void markAnythingOverdefined(Value *V) {
if (const StructType *STy = dyn_cast<StructType>(V->getType()))
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
markOverdefined(getStructValueState(V, i), V);
else
markOverdefined(V);
}
private:
// markConstant - Make a value be marked as "constant". If the value
// is not already a constant, add it to the instruction work list so that
@ -293,10 +321,12 @@ private:
}
void markConstant(Value *V, Constant *C) {
assert(!isa<StructType>(V->getType()) && "Should use other method");
markConstant(ValueState[V], V, C);
}
void markForcedConstant(Value *V, Constant *C) {
assert(!isa<StructType>(V->getType()) && "Should use other method");
ValueState[V].markForcedConstant(C);
DEBUG(errs() << "markForcedConstant: " << *C << ": " << *V << '\n');
InstWorkList.push_back(V);
@ -330,6 +360,7 @@ private:
}
void mergeInValue(Value *V, LatticeVal MergeWithV) {
assert(!isa<StructType>(V->getType()) && "Should use other method");
mergeInValue(ValueState[V], V, MergeWithV);
}
@ -338,8 +369,12 @@ private:
/// value. This function handles the case when the value hasn't been seen yet
/// by properly seeding constants etc.
LatticeVal &getValueState(Value *V) {
assert(!isa<StructType>(V->getType()) && "Should use getStructValueState");
// TODO: Change to do insert+find in one operation.
DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
if (I != ValueState.end()) return I->second; // Common case, in the map
if (I != ValueState.end())
return I->second; // Common case, already in the map.
LatticeVal &LV = ValueState[V];
@ -353,6 +388,39 @@ private:
return LV;
}
/// getStructValueState - Return the LatticeVal object that corresponds to the
/// value/field pair. This function handles the case when the value hasn't
/// been seen yet by properly seeding constants etc.
LatticeVal &getStructValueState(Value *V, unsigned i) {
assert(isa<StructType>(V->getType()) && "Should use getValueState");
assert(i < cast<StructType>(V->getType())->getNumElements() &&
"Invalid element #");
// TODO: Change to do insert+find in one operation.
DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator
I = StructValueState.find(std::make_pair(V, i));
if (I != StructValueState.end())
return I->second; // Common case, already in the map.
LatticeVal &LV = StructValueState[std::make_pair(V, i)];
if (Constant *C = dyn_cast<Constant>(V)) {
if (isa<UndefValue>(C))
; // Undef values remain undefined.
else if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C))
LV.markConstant(CS->getOperand(i)); // Constants are constant.
else if (isa<ConstantAggregateZero>(C)) {
const Type *FieldTy = cast<StructType>(V->getType())->getElementType(i);
LV.markConstant(Constant::getNullValue(FieldTy));
} else
LV.markOverdefined(); // Unknown sort of constant.
}
// All others are underdefined by default.
return LV;
}
/// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
/// work list if it is not already executable.
void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
@ -444,12 +512,12 @@ private:
void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
void visitAllocaInst (Instruction &I) { markOverdefined(&I); }
void visitVANextInst (Instruction &I) { markOverdefined(&I); }
void visitVAArgInst (Instruction &I) { markOverdefined(&I); }
void visitVAArgInst (Instruction &I) { markAnythingOverdefined(&I); }
void visitInstruction(Instruction &I) {
// If a new instruction is added to LLVM that we don't handle.
errs() << "SCCP: Don't know how to handle: " << I;
markOverdefined(&I); // Just in case
markAnythingOverdefined(&I); // Just in case
}
};
@ -596,6 +664,11 @@ bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
// successors executable.
//
void SCCPSolver::visitPHINode(PHINode &PN) {
// If this PN returns a struct, just mark the result overdefined.
// TODO: We could do a lot better than this if code actually uses this.
if (isa<StructType>(PN.getType()))
return markAnythingOverdefined(&PN);
if (getValueState(&PN).isOverdefined()) {
// There may be instructions using this PHI node that are not overdefined
// themselves. If so, make sure that they know that the PHI node operand
@ -617,7 +690,7 @@ void SCCPSolver::visitPHINode(PHINode &PN) {
// and slow us down a lot. Just mark them overdefined.
if (PN.getNumIncomingValues() > 64)
return markOverdefined(&PN);
// Look at all of the executable operands of the PHI node. If any of them
// are overdefined, the PHI becomes overdefined as well. If they are all
// constant, and they agree with each other, the PHI becomes the identical
@ -666,28 +739,26 @@ void SCCPSolver::visitReturnInst(ReturnInst &I) {
if (I.getNumOperands() == 0) return; // ret void
Function *F = I.getParent()->getParent();
Value *ResultOp = I.getOperand(0);
// If we are tracking the return value of this function, merge it in.
if (!TrackedRetVals.empty()) {
if (!TrackedRetVals.empty() && !isa<StructType>(ResultOp->getType())) {
DenseMap<Function*, LatticeVal>::iterator TFRVI =
TrackedRetVals.find(F);
if (TFRVI != TrackedRetVals.end()) {
mergeInValue(TFRVI->second, F, getValueState(I.getOperand(0)));
mergeInValue(TFRVI->second, F, getValueState(ResultOp));
return;
}
}
// Handle functions that return multiple values.
if (!TrackedMultipleRetVals.empty() &&
isa<StructType>(I.getOperand(0)->getType())) {
for (unsigned i = 0, e = I.getOperand(0)->getType()->getNumContainedTypes();
i != e; ++i) {
DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
It = TrackedMultipleRetVals.find(std::make_pair(F, i));
if (It == TrackedMultipleRetVals.end()) break;
if (Value *Val = FindInsertedValue(I.getOperand(0), i, I.getContext()))
mergeInValue(It->second, F, getValueState(Val));
}
if (!TrackedMultipleRetVals.empty()) {
if (const StructType *STy = dyn_cast<StructType>(ResultOp->getType()))
if (MRVFunctionsTracked.count(F))
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
getStructValueState(ResultOp, i));
}
}
@ -712,78 +783,62 @@ void SCCPSolver::visitCastInst(CastInst &I) {
OpSt.getConstant(), I.getType()));
}
void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
Value *Aggr = EVI.getAggregateOperand();
// If the operand to the extractvalue is an undef, the result is undef.
if (isa<UndefValue>(Aggr))
return;
// Currently only handle single-index extractvalues.
// If this returns a struct, mark all elements over defined, we don't track
// structs in structs.
if (isa<StructType>(EVI.getType()))
return markAnythingOverdefined(&EVI);
// If this is extracting from more than one level of struct, we don't know.
if (EVI.getNumIndices() != 1)
return markOverdefined(&EVI);
Function *F = 0;
if (CallInst *CI = dyn_cast<CallInst>(Aggr))
F = CI->getCalledFunction();
else if (InvokeInst *II = dyn_cast<InvokeInst>(Aggr))
F = II->getCalledFunction();
// TODO: If IPSCCP resolves the callee of this function, we could propagate a
// result back!
if (F == 0 || TrackedMultipleRetVals.empty())
return markOverdefined(&EVI);
// See if we are tracking the result of the callee. If not tracking this
// function (for example, it is a declaration) just move to overdefined.
if (!TrackedMultipleRetVals.count(std::make_pair(F, *EVI.idx_begin())))
return markOverdefined(&EVI);
// Otherwise, the value will be merged in here as a result of CallSite
// handling.
Value *AggVal = EVI.getAggregateOperand();
unsigned i = *EVI.idx_begin();
LatticeVal EltVal = getStructValueState(AggVal, i);
mergeInValue(getValueState(&EVI), &EVI, EltVal);
}
void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
Value *Aggr = IVI.getAggregateOperand();
Value *Val = IVI.getInsertedValueOperand();
// If the operands to the insertvalue are undef, the result is undef.
if (isa<UndefValue>(Aggr) && isa<UndefValue>(Val))
return;
// Currently only handle single-index insertvalues.
if (IVI.getNumIndices() != 1)
const StructType *STy = dyn_cast<StructType>(IVI.getType());
if (STy == 0)
return markOverdefined(&IVI);
// Currently only handle insertvalue instructions that are in a single-use
// chain that builds up a return value.
for (const InsertValueInst *TmpIVI = &IVI; ; ) {
if (!TmpIVI->hasOneUse())
return markOverdefined(&IVI);
const Value *V = *TmpIVI->use_begin();
if (isa<ReturnInst>(V))
break;
TmpIVI = dyn_cast<InsertValueInst>(V);
if (!TmpIVI)
return markOverdefined(&IVI);
}
// See if we are tracking the result of the callee.
Function *F = IVI.getParent()->getParent();
DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
It = TrackedMultipleRetVals.find(std::make_pair(F, *IVI.idx_begin()));
// Merge in the inserted member value.
if (It != TrackedMultipleRetVals.end())
mergeInValue(It->second, F, getValueState(Val));
// Mark the aggregate result of the IVI overdefined; any tracking that we do
// will be done on the individual member values.
markOverdefined(&IVI);
// If this has more than one index, we can't handle it, drive all results to
// undef.
if (IVI.getNumIndices() != 1)
return markAnythingOverdefined(&IVI);
Value *Aggr = IVI.getAggregateOperand();
unsigned Idx = *IVI.idx_begin();
// Compute the result based on what we're inserting.
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
// This passes through all values that aren't the inserted element.
if (i != Idx) {
LatticeVal EltVal = getStructValueState(Aggr, i);
mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
continue;
}
Value *Val = IVI.getInsertedValueOperand();
if (isa<StructType>(Val->getType()))
// We don't track structs in structs.
markOverdefined(getStructValueState(&IVI, i), &IVI);
else {
LatticeVal InVal = getValueState(Val);
mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
}
}
}
void SCCPSolver::visitSelectInst(SelectInst &I) {
// If this select returns a struct, just mark the result overdefined.
// TODO: We could do a lot better than this if code actually uses this.
if (isa<StructType>(I.getType()))
return markAnythingOverdefined(&I);
LatticeVal CondValue = getValueState(I.getCondition());
if (CondValue.isUndefined())
return;
@ -1011,7 +1066,7 @@ void SCCPSolver::visitCmpInst(CmpInst &I) {
}
void SCCPSolver::visitExtractElementInst(ExtractElementInst &I) {
// FIXME : SCCP does not handle vectors properly.
// TODO : SCCP does not handle vectors properly.
return markOverdefined(&I);
#if 0
@ -1027,7 +1082,7 @@ void SCCPSolver::visitExtractElementInst(ExtractElementInst &I) {
}
void SCCPSolver::visitInsertElementInst(InsertElementInst &I) {
// FIXME : SCCP does not handle vectors properly.
// TODO : SCCP does not handle vectors properly.
return markOverdefined(&I);
#if 0
LatticeVal &ValState = getValueState(I.getOperand(0));
@ -1051,7 +1106,7 @@ void SCCPSolver::visitInsertElementInst(InsertElementInst &I) {
}
void SCCPSolver::visitShuffleVectorInst(ShuffleVectorInst &I) {
// FIXME : SCCP does not handle vectors properly.
// TODO : SCCP does not handle vectors properly.
return markOverdefined(&I);
#if 0
LatticeVal &V1State = getValueState(I.getOperand(0));
@ -1105,6 +1160,10 @@ void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
}
void SCCPSolver::visitStoreInst(StoreInst &SI) {
// If this store is of a struct, ignore it.
if (isa<StructType>(SI.getOperand(0)->getType()))
return;
if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
return;
@ -1122,6 +1181,10 @@ void SCCPSolver::visitStoreInst(StoreInst &SI) {
// Handle load instructions. If the operand is a constant pointer to a constant
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
// If this load is of a struct, just mark the result overdefined.
if (isa<StructType>(I.getType()))
return markAnythingOverdefined(&I);
LatticeVal PtrVal = getValueState(I.getOperand(0));
if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
@ -1196,7 +1259,7 @@ CallOverdefined:
}
// Otherwise, we don't know anything about this call, mark it overdefined.
return markOverdefined(I);
return markAnythingOverdefined(I);
}
// If this is a local function that doesn't have its address taken, mark its
@ -1216,47 +1279,33 @@ CallOverdefined:
continue;
}
mergeInValue(AI, getValueState(*CAI));
if (const StructType *STy = dyn_cast<StructType>(AI->getType())) {
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
mergeInValue(getStructValueState(AI, i), AI,
getStructValueState(*CAI, i));
} else {
mergeInValue(AI, getValueState(*CAI));
}
}
}
// If this is a single/zero retval case, see if we're tracking the function.
DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
if (TFRVI != TrackedRetVals.end()) {
if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
if (!MRVFunctionsTracked.count(F))
goto CallOverdefined; // Not tracking this callee.
// If we are tracking this callee, propagate the result of the function
// into this call site.
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
mergeInValue(getStructValueState(I, i), I,
TrackedMultipleRetVals[std::make_pair(F, i)]);
} else {
DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
if (TFRVI == TrackedRetVals.end())
goto CallOverdefined; // Not tracking this callee.
// If so, propagate the return value of the callee into this call result.
mergeInValue(I, TFRVI->second);
} else if (isa<StructType>(I->getType())) {
// Check to see if we're tracking this callee, if not, handle it in the
// common path above.
DenseMap<std::pair<Function*, unsigned>, LatticeVal>::iterator
TMRVI = TrackedMultipleRetVals.find(std::make_pair(F, 0));
if (TMRVI == TrackedMultipleRetVals.end())
goto CallOverdefined;
// Need to mark as overdefined, otherwise it stays undefined which
// creates extractvalue undef, <idx>
markOverdefined(I);
// If we are tracking this callee, propagate the return values of the call
// into this call site. We do this by walking all the uses. Single-index
// ExtractValueInst uses can be tracked; anything more complicated is
// currently handled conservatively.
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(*UI)) {
if (EVI->getNumIndices() == 1) {
mergeInValue(EVI,
TrackedMultipleRetVals[std::make_pair(F, *EVI->idx_begin())]);
continue;
}
}
// The aggregate value is used in a way not handled here. Assume nothing.
markOverdefined(*UI);
}
} else {
// Otherwise we're not tracking this callee, so handle it in the
// common path above.
goto CallOverdefined;
}
}
@ -1297,7 +1346,7 @@ void SCCPSolver::Solve() {
// since all of its users will have already been marked as overdefined.
// Update all of the users of this instruction's value.
//
if (!getValueState(I).isOverdefined())
if (isa<StructType>(I->getType()) || !getValueState(I).isOverdefined())
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
if (Instruction *I = dyn_cast<Instruction>(*UI))
@ -1345,13 +1394,35 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
// Look for instructions which produce undef values.
if (I->getType()->isVoidTy()) continue;
if (const StructType *STy = dyn_cast<StructType>(I->getType())) {
// Only a few things that can be structs matter for undef. Just send
// all their results to overdefined. We could be more precise than this
// but it isn't worth bothering.
if (isa<CallInst>(I) || isa<SelectInst>(I)) {
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
LatticeVal &LV = getStructValueState(I, i);
if (LV.isUndefined())
markOverdefined(LV, I);
}
}
continue;
}
LatticeVal &LV = getValueState(I);
if (!LV.isUndefined()) continue;
// No instructions using structs need disambiguation.
if (isa<StructType>(I->getOperand(0)->getType()))
continue;
// Get the lattice values of the first two operands for use below.
LatticeVal Op0LV = getValueState(I->getOperand(0));
LatticeVal Op1LV;
if (I->getNumOperands() == 2) {
// No instructions using structs need disambiguation.
if (isa<StructType>(I->getOperand(1)->getType()))
continue;
// If this is a two-operand instruction, and if both operands are
// undefs, the result stays undef.
Op1LV = getValueState(I->getOperand(1));
@ -1547,7 +1618,7 @@ bool SCCP::runOnFunction(Function &F) {
// Mark all arguments to the function as being overdefined.
for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;++AI)
Solver.markOverdefined(AI);
Solver.markAnythingOverdefined(AI);
// Solve for constants.
bool ResolvedUndefs = true;
@ -1578,6 +1649,10 @@ bool SCCP::runOnFunction(Function &F) {
if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
continue;
// TODO: Reconstruct structs from their elements.
if (isa<StructType>(Inst->getType()))
continue;
LatticeVal IV = Solver.getLatticeValueFor(Inst);
if (IV.isOverdefined())
continue;
@ -1661,8 +1736,7 @@ bool IPSCCP::runOnModule(Module &M) {
// If this is a strong or ODR definition of this function, then we can
// propagate information about its result into callsites of it.
if (!F->mayBeOverridden() &&
!isa<StructType>(F->getReturnType()))
if (!F->mayBeOverridden())
Solver.AddTrackedFunction(F);
// If this function only has direct calls that we can see, we can track its
@ -1679,7 +1753,7 @@ bool IPSCCP::runOnModule(Module &M) {
// Assume nothing about the incoming arguments.
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI)
Solver.markOverdefined(AI);
Solver.markAnythingOverdefined(AI);
}
// Loop over global variables. We inform the solver about any internal global
@ -1712,8 +1786,11 @@ bool IPSCCP::runOnModule(Module &M) {
if (Solver.isBlockExecutable(F->begin())) {
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI) {
if (AI->use_empty()) continue;
if (AI->use_empty() || isa<StructType>(AI->getType())) continue;
// TODO: Could use getStructLatticeValueFor to find out if the entire
// result is a constant and replace it entirely if so.
LatticeVal IV = Solver.getLatticeValueFor(AI);
if (IV.isOverdefined()) continue;
@ -1752,9 +1829,12 @@ bool IPSCCP::runOnModule(Module &M) {
for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
Instruction *Inst = BI++;
if (Inst->getType()->isVoidTy())
if (Inst->getType()->isVoidTy() || isa<StructType>(Inst->getType()))
continue;
// TODO: Could use getStructLatticeValueFor to find out if the entire
// result is a constant and replace it entirely if so.
LatticeVal IV = Solver.getLatticeValueFor(Inst);
if (IV.isOverdefined())
continue;

3
test/Transforms/SCCP/ipsccp-basic.ll
View File

@ -1,5 +1,4 @@
; RUN: opt < %s -ipsccp -S | FileCheck %s
; XFAIL: *
;;======================== test1
@ -128,7 +127,7 @@ B:
; CHECK: define i64 @test5b()
; CHECK: A:
; CHECK-NEXT: %c = call i64 @test5c(%0 %a)
; CHECK-NEXT: ret i64 %c
; CHECK-NEXT: ret i64 5
define internal i64 @test5c({i64,i64} %a) {
%b = extractvalue {i64,i64} %a, 0