#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <map>
#include <set>
#include <tuple>
typedef SmallVector<RetOrArg, 5> UseVector;
- // Map each LLVM function to corresponding metadata with debug info. If
- // the function is replaced with another one, we should patch the pointer
- // to LLVM function in metadata.
- // As the code generation for module is finished (and DIBuilder is
- // finalized) we assume that subprogram descriptors won't be changed, and
- // they are stored in map for short duration anyway.
- DenseMap<const Function *, DISubprogram> FunctionDIs;
-
protected:
// DAH uses this to specify a different ID.
explicit DAE(char &ID) : ModulePass(ID) {}
if (Fn.hasAddressTaken())
return false;
+ // Don't touch naked functions. The assembly might be using an argument, or
+ // otherwise rely on the frame layout in a way that this analysis will not
+ // see.
+ if (Fn.hasFnAttribute(Attribute::Naked)) {
+ return false;
+ }
+
// Okay, we know we can transform this function if safe. Scan its body
// looking for calls marked musttail or calls to llvm.vastart.
for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
// Create the new function body and insert it into the module...
Function *NF = Function::Create(NFTy, Fn.getLinkage());
NF->copyAttributesFrom(&Fn);
- Fn.getParent()->getFunctionList().insert(&Fn, NF);
+ Fn.getParent()->getFunctionList().insert(Fn.getIterator(), NF);
NF->takeName(&Fn);
// Loop over all of the callers of the function, transforming the call sites
for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end(),
I2 = NF->arg_begin(); I != E; ++I, ++I2) {
// Move the name and users over to the new version.
- I->replaceAllUsesWith(I2);
- I2->takeName(I);
+ I->replaceAllUsesWith(&*I2);
+ I2->takeName(&*I);
}
// Patch the pointer to LLVM function in debug info descriptor.
- auto DI = FunctionDIs.find(&Fn);
- if (DI != FunctionDIs.end()) {
- DISubprogram SP = DI->second;
- SP.replaceFunction(NF);
- // Ensure the map is updated so it can be reused on non-varargs argument
- // eliminations of the same function.
- FunctionDIs.erase(DI);
- FunctionDIs[NF] = SP;
- }
+ NF->setSubprogram(Fn.getSubprogram());
// Fix up any BlockAddresses that refer to the function.
Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
/// instead.
bool DAE::RemoveDeadArgumentsFromCallers(Function &Fn)
{
- if (Fn.isDeclaration() || Fn.mayBeOverridden())
+ // We cannot change the arguments if this TU does not define the function or
+ // if the linker may choose a function body from another TU, even if the
+ // nominal linkage indicates that other copies of the function have the same
+ // semantics. In the below example, the dead load from %p may not have been
+ // eliminated from the linker-chosen copy of f, so replacing %p with undef
+ // in callers may introduce undefined behavior.
+ //
+ // define linkonce_odr void @f(i32* %p) {
+ // %v = load i32 %p
+ // ret void
+ // }
+ if (!Fn.isStrongDefinitionForLinker())
return false;
// Functions with local linkage should already have been handled, except the
if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
return false;
- // If a function seen at compile time is not necessarily the one linked to
- // the binary being built, it is illegal to change the actual arguments
- // passed to it. These functions can be captured by isWeakForLinker().
- // *NOTE* that mayBeOverridden() is insufficient for this purpose as it
- // doesn't include linkage types like AvailableExternallyLinkage and
- // LinkOnceODRLinkage. Take link_odr* as an example, it indicates a set of
- // *EQUIVALENT* globals that can be merged at link-time. However, the
- // semantic of *EQUIVALENT*-functions includes parameters. Changing
- // parameters breaks this assumption.
- //
- if (Fn.isWeakForLinker())
+ // Don't touch naked functions. The assembly might be using an argument, or
+ // otherwise rely on the frame layout in a way that this analysis will not
+ // see.
+ if (Fn.hasFnAttribute(Attribute::Naked))
return false;
if (Fn.use_empty())
return false;
SmallVector<unsigned, 8> UnusedArgs;
- for (Function::arg_iterator I = Fn.arg_begin(), E = Fn.arg_end();
- I != E; ++I) {
- Argument *Arg = I;
-
- if (Arg->use_empty() && !Arg->hasByValOrInAllocaAttr())
- UnusedArgs.push_back(Arg->getArgNo());
+ for (Argument &Arg : Fn.args()) {
+ if (Arg.use_empty() && !Arg.hasByValOrInAllocaAttr())
+ UnusedArgs.push_back(Arg.getArgNo());
}
if (UnusedArgs.empty())
return Result;
}
- if (ImmutableCallSite CS = V) {
+ if (auto CS = ImmutableCallSite(V)) {
const Function *F = CS.getCalledFunction();
if (F) {
// Used in a direct call.
+ // The function argument is live if it is used as a bundle operand.
+ if (CS.isBundleOperand(U))
+ return Live;
+
// Find the argument number. We know for sure that this use is an
// argument, since if it was the function argument this would be an
// indirect call and the we know can't be looking at a value of the
return;
}
+ // Don't touch naked functions. The assembly might be using an argument, or
+ // otherwise rely on the frame layout in a way that this analysis will not
+ // see.
+ if (F.hasFnAttribute(Attribute::Naked)) {
+ MarkLive(F);
+ return;
+ }
+
unsigned RetCount = NumRetVals(&F);
// Assume all return values are dead
typedef SmallVector<Liveness, 5> RetVals;
} else {
// See what the effect of this use is (recording any uses that cause
// MaybeLive in MaybeLiveArgUses).
- Result = SurveyUses(AI, MaybeLiveArgUses);
+ Result = SurveyUses(&*AI, MaybeLiveArgUses);
}
// Mark the result.
// here. Currently, this should not be possible, but special handling might be
// required when new return value attributes are added.
if (NRetTy->isVoidTy())
- RAttrs =
- AttributeSet::get(NRetTy->getContext(), AttributeSet::ReturnIndex,
- AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- removeAttributes(AttributeFuncs::
- typeIncompatible(NRetTy, AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex));
+ RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
+ AttributeSet::ReturnIndex,
+ AttributeFuncs::typeIncompatible(NRetTy));
else
assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- hasAttributes(AttributeFuncs::
- typeIncompatible(NRetTy, AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex) &&
+ overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
"Return attributes no longer compatible?");
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
NF->setAttributes(NewPAL);
// Insert the new function before the old function, so we won't be processing
// it again.
- F->getParent()->getFunctionList().insert(F, NF);
+ F->getParent()->getFunctionList().insert(F->getIterator(), NF);
NF->takeName(F);
// Loop over all of the callers of the function, transforming the call sites
AttributeSet RAttrs = CallPAL.getRetAttributes();
// Adjust in case the function was changed to return void.
- RAttrs =
- AttributeSet::get(NF->getContext(), AttributeSet::ReturnIndex,
- AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
- removeAttributes(AttributeFuncs::
- typeIncompatible(NF->getReturnType(),
- AttributeSet::ReturnIndex),
- AttributeSet::ReturnIndex));
+ RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
+ AttributeSet::ReturnIndex,
+ AttributeFuncs::typeIncompatible(NF->getReturnType()));
if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
AttributesVec.push_back(AttributeSet::get(NF->getContext(), RAttrs));
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
- Args, "", Call);
+ Args, "", Call->getParent());
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
cast<InvokeInst>(New)->setAttributes(NewCallPAL);
} else {
" must have been a struct or an array!");
Instruction *InsertPt = Call;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- BasicBlock::iterator IP = II->getNormalDest()->begin();
- while (isa<PHINode>(IP)) ++IP;
- InsertPt = IP;
+ BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
+ InsertPt = &*NewEdge->getFirstInsertionPt();
}
// We used to return a struct or array. Instead of doing smart stuff
if (ArgAlive[i]) {
// If this is a live argument, move the name and users over to the new
// version.
- I->replaceAllUsesWith(I2);
- I2->takeName(I);
+ I->replaceAllUsesWith(&*I2);
+ I2->takeName(&*I);
++I2;
} else {
// If this argument is dead, replace any uses of it with null constants
}
// Patch the pointer to LLVM function in debug info descriptor.
- auto DI = FunctionDIs.find(F);
- if (DI != FunctionDIs.end())
- DI->second.replaceFunction(NF);
+ NF->setSubprogram(F->getSubprogram());
// Now that the old function is dead, delete it.
F->eraseFromParent();
bool DAE::runOnModule(Module &M) {
bool Changed = false;
- // Collect debug info descriptors for functions.
- FunctionDIs = makeSubprogramMap(M);
-
// First pass: Do a simple check to see if any functions can have their "..."
// removed. We can do this if they never call va_start. This loop cannot be
// fused with the next loop, because deleting a function invalidates
for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
// Increment now, because the function will probably get removed (ie.
// replaced by a new one).
- Function *F = I++;
+ Function *F = &*I++;
Changed |= RemoveDeadStuffFromFunction(F);
}
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