aboutsummaryrefslogtreecommitdiff
path: root/lib/Transforms/IPO/FunctionAttrs.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'lib/Transforms/IPO/FunctionAttrs.cpp')
-rw-r--r--lib/Transforms/IPO/FunctionAttrs.cpp150
1 files changed, 95 insertions, 55 deletions
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index 402a66552c24..4d13b3f40688 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -49,31 +49,35 @@ STATISTIC(NumNoAlias, "Number of function returns marked noalias");
STATISTIC(NumNonNullReturn, "Number of function returns marked nonnull");
STATISTIC(NumNoRecurse, "Number of functions marked as norecurse");
-namespace {
-typedef SmallSetVector<Function *, 8> SCCNodeSet;
-}
+// FIXME: This is disabled by default to avoid exposing security vulnerabilities
+// in C/C++ code compiled by clang:
+// http://lists.llvm.org/pipermail/cfe-dev/2017-January/052066.html
+static cl::opt<bool> EnableNonnullArgPropagation(
+ "enable-nonnull-arg-prop", cl::Hidden,
+ cl::desc("Try to propagate nonnull argument attributes from callsites to "
+ "caller functions."));
namespace {
-/// The three kinds of memory access relevant to 'readonly' and
-/// 'readnone' attributes.
-enum MemoryAccessKind {
- MAK_ReadNone = 0,
- MAK_ReadOnly = 1,
- MAK_MayWrite = 2
-};
+typedef SmallSetVector<Function *, 8> SCCNodeSet;
}
-static MemoryAccessKind checkFunctionMemoryAccess(Function &F, AAResults &AAR,
+/// Returns the memory access attribute for function F using AAR for AA results,
+/// where SCCNodes is the current SCC.
+///
+/// If ThisBody is true, this function may examine the function body and will
+/// return a result pertaining to this copy of the function. If it is false, the
+/// result will be based only on AA results for the function declaration; it
+/// will be assumed that some other (perhaps less optimized) version of the
+/// function may be selected at link time.
+static MemoryAccessKind checkFunctionMemoryAccess(Function &F, bool ThisBody,
+ AAResults &AAR,
const SCCNodeSet &SCCNodes) {
FunctionModRefBehavior MRB = AAR.getModRefBehavior(&F);
if (MRB == FMRB_DoesNotAccessMemory)
// Already perfect!
return MAK_ReadNone;
- // Non-exact function definitions may not be selected at link time, and an
- // alternative version that writes to memory may be selected. See the comment
- // on GlobalValue::isDefinitionExact for more details.
- if (!F.hasExactDefinition()) {
+ if (!ThisBody) {
if (AliasAnalysis::onlyReadsMemory(MRB))
return MAK_ReadOnly;
@@ -172,9 +176,14 @@ static MemoryAccessKind checkFunctionMemoryAccess(Function &F, AAResults &AAR,
return ReadsMemory ? MAK_ReadOnly : MAK_ReadNone;
}
+MemoryAccessKind llvm::computeFunctionBodyMemoryAccess(Function &F,
+ AAResults &AAR) {
+ return checkFunctionMemoryAccess(F, /*ThisBody=*/true, AAR, {});
+}
+
/// Deduce readonly/readnone attributes for the SCC.
template <typename AARGetterT>
-static bool addReadAttrs(const SCCNodeSet &SCCNodes, AARGetterT AARGetter) {
+static bool addReadAttrs(const SCCNodeSet &SCCNodes, AARGetterT &&AARGetter) {
// 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;
@@ -182,7 +191,11 @@ static bool addReadAttrs(const SCCNodeSet &SCCNodes, AARGetterT AARGetter) {
// Call the callable parameter to look up AA results for this function.
AAResults &AAR = AARGetter(*F);
- switch (checkFunctionMemoryAccess(*F, AAR, SCCNodes)) {
+ // Non-exact function definitions may not be selected at link time, and an
+ // alternative version that writes to memory may be selected. See the
+ // comment on GlobalValue::isDefinitionExact for more details.
+ switch (checkFunctionMemoryAccess(*F, F->hasExactDefinition(),
+ AAR, SCCNodes)) {
case MAK_MayWrite:
return false;
case MAK_ReadOnly:
@@ -212,11 +225,11 @@ static bool addReadAttrs(const SCCNodeSet &SCCNodes, AARGetterT AARGetter) {
AttrBuilder B;
B.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
F->removeAttributes(
- AttributeSet::FunctionIndex,
- AttributeSet::get(F->getContext(), AttributeSet::FunctionIndex, B));
+ AttributeList::FunctionIndex,
+ AttributeList::get(F->getContext(), AttributeList::FunctionIndex, B));
// Add in the new attribute.
- F->addAttribute(AttributeSet::FunctionIndex,
+ F->addAttribute(AttributeList::FunctionIndex,
ReadsMemory ? Attribute::ReadOnly : Attribute::ReadNone);
if (ReadsMemory)
@@ -522,7 +535,7 @@ static bool addArgumentReturnedAttrs(const SCCNodeSet &SCCNodes) {
if (Value *RetArg = FindRetArg()) {
auto *A = cast<Argument>(RetArg);
- A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
+ A->addAttr(AttributeList::get(F->getContext(), A->getArgNo() + 1, B));
++NumReturned;
Changed = true;
}
@@ -531,6 +544,49 @@ static bool addArgumentReturnedAttrs(const SCCNodeSet &SCCNodes) {
return Changed;
}
+/// If a callsite has arguments that are also arguments to the parent function,
+/// try to propagate attributes from the callsite's arguments to the parent's
+/// arguments. This may be important because inlining can cause information loss
+/// when attribute knowledge disappears with the inlined call.
+static bool addArgumentAttrsFromCallsites(Function &F) {
+ if (!EnableNonnullArgPropagation)
+ return false;
+
+ bool Changed = false;
+
+ // For an argument attribute to transfer from a callsite to the parent, the
+ // call must be guaranteed to execute every time the parent is called.
+ // Conservatively, just check for calls in the entry block that are guaranteed
+ // to execute.
+ // TODO: This could be enhanced by testing if the callsite post-dominates the
+ // entry block or by doing simple forward walks or backward walks to the
+ // callsite.
+ BasicBlock &Entry = F.getEntryBlock();
+ for (Instruction &I : Entry) {
+ if (auto CS = CallSite(&I)) {
+ if (auto *CalledFunc = CS.getCalledFunction()) {
+ for (auto &CSArg : CalledFunc->args()) {
+ if (!CSArg.hasNonNullAttr())
+ continue;
+
+ // If the non-null callsite argument operand is an argument to 'F'
+ // (the caller) and the call is guaranteed to execute, then the value
+ // must be non-null throughout 'F'.
+ auto *FArg = dyn_cast<Argument>(CS.getArgOperand(CSArg.getArgNo()));
+ if (FArg && !FArg->hasNonNullAttr()) {
+ FArg->addAttr(Attribute::NonNull);
+ Changed = true;
+ }
+ }
+ }
+ }
+ if (!isGuaranteedToTransferExecutionToSuccessor(&I))
+ break;
+ }
+
+ return Changed;
+}
+
/// Deduce nocapture attributes for the SCC.
static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
bool Changed = false;
@@ -549,6 +605,8 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
if (!F->hasExactDefinition())
continue;
+ Changed |= addArgumentAttrsFromCallsites(*F);
+
// Functions that are readonly (or readnone) and nounwind and don't return
// a value can't capture arguments. Don't analyze them.
if (F->onlyReadsMemory() && F->doesNotThrow() &&
@@ -556,7 +614,7 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E;
++A) {
if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr()) {
- A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
+ A->addAttr(AttributeList::get(F->getContext(), A->getArgNo() + 1, B));
++NumNoCapture;
Changed = true;
}
@@ -576,7 +634,7 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
if (Tracker.Uses.empty()) {
// If it's trivially not captured, mark it nocapture now.
A->addAttr(
- AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
+ AttributeList::get(F->getContext(), A->getArgNo() + 1, B));
++NumNoCapture;
Changed = true;
} else {
@@ -604,7 +662,7 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
if (R != Attribute::None) {
AttrBuilder B;
B.addAttribute(R);
- A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
+ A->addAttr(AttributeList::get(A->getContext(), A->getArgNo() + 1, B));
Changed = true;
R == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
}
@@ -629,7 +687,7 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
if (ArgumentSCC[0]->Uses.size() == 1 &&
ArgumentSCC[0]->Uses[0] == ArgumentSCC[0]) {
Argument *A = ArgumentSCC[0]->Definition;
- A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
+ A->addAttr(AttributeList::get(A->getContext(), A->getArgNo() + 1, B));
++NumNoCapture;
Changed = true;
}
@@ -671,7 +729,7 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
Argument *A = ArgumentSCC[i]->Definition;
- A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
+ A->addAttr(AttributeList::get(A->getContext(), A->getArgNo() + 1, B));
++NumNoCapture;
Changed = true;
}
@@ -708,8 +766,9 @@ static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
Argument *A = ArgumentSCC[i]->Definition;
// Clear out existing readonly/readnone attributes
- A->removeAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, R));
- A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
+ A->removeAttr(
+ AttributeList::get(A->getContext(), A->getArgNo() + 1, R));
+ A->addAttr(AttributeList::get(A->getContext(), A->getArgNo() + 1, B));
ReadAttr == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
Changed = true;
}
@@ -769,7 +828,7 @@ static bool isFunctionMallocLike(Function *F, const SCCNodeSet &SCCNodes) {
case Instruction::Call:
case Instruction::Invoke: {
CallSite CS(RVI);
- if (CS.paramHasAttr(0, Attribute::NoAlias))
+ if (CS.hasRetAttr(Attribute::NoAlias))
break;
if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
break;
@@ -905,7 +964,7 @@ static bool addNonNullAttrs(const SCCNodeSet &SCCNodes) {
// pointers.
for (Function *F : SCCNodes) {
// Already nonnull.
- if (F->getAttributes().hasAttribute(AttributeSet::ReturnIndex,
+ if (F->getAttributes().hasAttribute(AttributeList::ReturnIndex,
Attribute::NonNull))
continue;
@@ -926,7 +985,7 @@ static bool addNonNullAttrs(const SCCNodeSet &SCCNodes) {
// Mark the function eagerly since we may discover a function
// which prevents us from speculating about the entire SCC
DEBUG(dbgs() << "Eagerly marking " << F->getName() << " as nonnull\n");
- F->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+ F->addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
++NumNonNullReturn;
MadeChange = true;
}
@@ -939,13 +998,13 @@ static bool addNonNullAttrs(const SCCNodeSet &SCCNodes) {
if (SCCReturnsNonNull) {
for (Function *F : SCCNodes) {
- if (F->getAttributes().hasAttribute(AttributeSet::ReturnIndex,
+ if (F->getAttributes().hasAttribute(AttributeList::ReturnIndex,
Attribute::NonNull) ||
!F->getReturnType()->isPointerTy())
continue;
DEBUG(dbgs() << "SCC marking " << F->getName() << " as nonnull\n");
- F->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+ F->addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
++NumNonNullReturn;
MadeChange = true;
}
@@ -1163,19 +1222,7 @@ static bool runImpl(CallGraphSCC &SCC, AARGetterT AARGetter) {
bool PostOrderFunctionAttrsLegacyPass::runOnSCC(CallGraphSCC &SCC) {
if (skipSCC(SCC))
return false;
-
- // We compute dedicated AA results for each function in the SCC as needed. We
- // use a lambda referencing external objects so that they live long enough to
- // be queried, but we re-use them each time.
- Optional<BasicAAResult> BAR;
- Optional<AAResults> AAR;
- auto AARGetter = [&](Function &F) -> AAResults & {
- BAR.emplace(createLegacyPMBasicAAResult(*this, F));
- AAR.emplace(createLegacyPMAAResults(*this, F, *BAR));
- return *AAR;
- };
-
- return runImpl(SCC, AARGetter);
+ return runImpl(SCC, LegacyAARGetter(*this));
}
namespace {
@@ -1275,16 +1322,9 @@ PreservedAnalyses
ReversePostOrderFunctionAttrsPass::run(Module &M, ModuleAnalysisManager &AM) {
auto &CG = AM.getResult<CallGraphAnalysis>(M);
- bool Changed = deduceFunctionAttributeInRPO(M, CG);
-
- // CallGraphAnalysis holds AssertingVH and must be invalidated eagerly so
- // that other passes don't delete stuff from under it.
- // FIXME: We need to invalidate this to avoid PR28400. Is there a better
- // solution?
- AM.invalidate<CallGraphAnalysis>(M);
-
- if (!Changed)
+ if (!deduceFunctionAttributeInRPO(M, CG))
return PreservedAnalyses::all();
+
PreservedAnalyses PA;
PA.preserve<CallGraphAnalysis>();
return PA;
generated by cgit v1.2.3 (git 2.25.1) at 2025-08-11 13:32:57 +0000