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[FuncComp] Compare MDNodes in cmpMetadata using cmpMDNode. #128878

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[FuncComp] Compare MDNodes in cmpMetadata using cmpMDNode. #128878

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5 changes: 3 additions & 2 deletions llvm/include/llvm/Transforms/Utils/FunctionComparator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -328,8 +328,9 @@ class FunctionComparator {
int cmpOrderings(AtomicOrdering L, AtomicOrdering R) const;
int cmpInlineAsm(const InlineAsm *L, const InlineAsm *R) const;
int cmpAttrs(const AttributeList L, const AttributeList R) const;
int cmpMDNode(const MDNode *L, const MDNode *R) const;
int cmpMetadata(const Metadata *L, const Metadata *R) const;
int cmpMDNode(const MDNode *L, const MDNode *R, bool InValueContext) const;
int cmpMetadata(const Metadata *L, const Metadata *R,
bool InValueContext) const;
int cmpInstMetadata(Instruction const *L, Instruction const *R) const;
int cmpOperandBundlesSchema(const CallBase &LCS, const CallBase &RCS) const;

Expand Down
38 changes: 38 additions & 0 deletions llvm/lib/IR/Verifier.cpp
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Expand Up @@ -3543,6 +3543,31 @@ void Verifier::visitPHINode(PHINode &PN) {
visitInstruction(PN);
}

/// Returns true of \p MD is valid for as a metadata argument. It must be on of
/// the following
/// * a MDNode without cycles (expect self-reference in the first operand),
/// * MDString,
/// * ValueAsMetadata.
static bool isValidMetadataArgument(const Metadata *MD,
SmallPtrSetImpl<const Metadata *> &Seen) {
// Potential cycles are not allowed.
if (!Seen.insert(MD).second)
return false;

if (auto *Node = dyn_cast<MDNode>(MD)) {
if (Node->getNumOperands() == 0)
return true;
ArrayRef<MDOperand> Ops = Node->operands();
if (Node->getOperand(0) == Node)
Ops = Ops.drop_front();
return all_of(Ops, [&](const Metadata *MD) {
return MD && isValidMetadataArgument(MD, Seen);
});
}

return isa<MDString>(MD) || isa<ValueAsMetadata>(MD);
}

void Verifier::visitCallBase(CallBase &Call) {
Check(Call.getCalledOperand()->getType()->isPointerTy(),
"Called function must be a pointer!", Call);
Expand All @@ -3562,6 +3587,19 @@ void Verifier::visitCallBase(CallBase &Call) {
"Call parameter type does not match function signature!",
Call.getArgOperand(i), FTy->getParamType(i), Call);

// Verify metadata arguments.
for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
auto Arg = Call.getArgOperand(i);
if (!Arg->getType()->isMetadataTy() || isa<DbgInfoIntrinsic>(Call))
continue;
SmallPtrSet<const Metadata *, 4> Seen;
Check(isValidMetadataArgument(cast<MetadataAsValue>(Arg)->getMetadata(),
Seen),
"Function arguments must be string metadata, value-as-metadata or an "
"MDNode!",
Call);
}

AttributeList Attrs = Call.getAttributes();

Check(verifyAttributeCount(Attrs, Call.arg_size()),
Expand Down
61 changes: 44 additions & 17 deletions llvm/lib/Transforms/Utils/FunctionComparator.cpp
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Expand Up @@ -185,38 +185,53 @@ int FunctionComparator::cmpAttrs(const AttributeList L,
return 0;
}

int FunctionComparator::cmpMetadata(const Metadata *L,
const Metadata *R) const {
int FunctionComparator::cmpMetadata(const Metadata *L, const Metadata *R,
bool InValueContext) const {
// TODO: the following routine coerce the metadata contents into constants
// or MDStrings before comparison.
// It ignores any other cases, so that the metadata nodes are considered
// equal even though this is not correct.
// We should structurally compare the metadata nodes to be perfect here.

if (L == R)
return 0;

auto *MDStringL = dyn_cast<MDString>(L);
auto *MDStringR = dyn_cast<MDString>(R);
if (MDStringL && MDStringR) {
if (MDStringL == MDStringR)
return 0;
if (MDStringL && MDStringR)
return MDStringL->getString().compare(MDStringR->getString());
}
if (MDStringR)
return -1;
if (MDStringL)
return 1;

auto *CL = dyn_cast<ConstantAsMetadata>(L);
auto *CR = dyn_cast<ConstantAsMetadata>(R);
if (CL == CR)
return 0;
if (!CL)
if (CL && CR)
return cmpConstants(CL->getValue(), CR->getValue());
if (CR)
return -1;
if (!CR)
if (CL)
return 1;
return cmpConstants(CL->getValue(), CR->getValue());

auto *NodeL = dyn_cast<MDNode>(L);
auto *NodeR = dyn_cast<MDNode>(R);
if (NodeL && NodeR) {
if (InValueContext)
return cmpMDNode(NodeL, NodeR, InValueContext);
} else {
if (NodeR)
return -1;
if (NodeL)
return 1;
}
assert(!InValueContext &&
"all cases must be handled when comparing metadata arguments");
return 0;
}

int FunctionComparator::cmpMDNode(const MDNode *L, const MDNode *R) const {
int FunctionComparator::cmpMDNode(const MDNode *L, const MDNode *R,
bool InValueContext) const {
if (L == R)
return 0;
if (!L)
Expand All @@ -231,8 +246,20 @@ int FunctionComparator::cmpMDNode(const MDNode *L, const MDNode *R) const {
// function semantically.
if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
return Res;
for (size_t I = 0; I < L->getNumOperands(); ++I)
if (int Res = cmpMetadata(L->getOperand(I), R->getOperand(I)))

size_t StartIdx = 0;
if (L->getNumOperands() > 0) {
if (L->getOperand(0) == L) {
if (R->getOperand(0) != R)
return -1;
StartIdx = 1;
} else if (R->getOperand(0) == R)
return 1;
}

for (size_t I = StartIdx; I < L->getNumOperands(); ++I)
if (int Res =
cmpMetadata(L->getOperand(I), R->getOperand(I), InValueContext))
return Res;
return 0;
}
Expand All @@ -254,7 +281,7 @@ int FunctionComparator::cmpInstMetadata(Instruction const *L,
auto const [KeyR, MR] = MDR[I];
if (int Res = cmpNumbers(KeyL, KeyR))
return Res;
if (int Res = cmpMDNode(ML, MR))
if (int Res = cmpMDNode(ML, MR, false))
return Res;
}
return 0;
Expand Down Expand Up @@ -722,7 +749,7 @@ int FunctionComparator::cmpOperations(const Instruction *L,
cast<CallInst>(R)->getTailCallKind()))
return Res;
return cmpMDNode(L->getMetadata(LLVMContext::MD_range),
R->getMetadata(LLVMContext::MD_range));
R->getMetadata(LLVMContext::MD_range), false);
}
if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(L)) {
ArrayRef<unsigned> LIndices = IVI->getIndices();
Expand Down Expand Up @@ -899,7 +926,7 @@ int FunctionComparator::cmpValues(const Value *L, const Value *R) const {
return 0;

return cmpMetadata(MetadataValueL->getMetadata(),
MetadataValueR->getMetadata());
MetadataValueR->getMetadata(), true);
}

if (MetadataValueL)
Expand Down
40 changes: 21 additions & 19 deletions llvm/test/Transforms/MergeFunc/metadata-call-arguments.ll
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Expand Up @@ -55,48 +55,50 @@ declare i64 @llvm.read_volatile_register.i64(metadata)

!5 = !{!"foo", i64 10}
!6 = !{!"foo", i64 10}
; CHECK-LABEL: define i64 @call_mdtuple_arg_not_equal_1() {
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META0:![0-9]+]])
; CHECK-NEXT: ret i64 [[TMP1]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_not_equal_2() {
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META1:![0-9]+]])
; CHECK-NEXT: ret i64 [[TMP1]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_with_cycle_equal_1() {
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META0:![0-9]+]])
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META2:![0-9]+]])
; CHECK-NEXT: ret i64 [[R]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_with_cycle_equal_2() {
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META1:![0-9]+]])
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META3:![0-9]+]])
; CHECK-NEXT: ret i64 [[R]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_with_cycle_not_equal_1() {
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META1]])
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META3]])
; CHECK-NEXT: ret i64 [[R]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_with_cycle_not_equal_2() {
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META2:![0-9]+]])
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META4:![0-9]+]])
; CHECK-NEXT: ret i64 [[R]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_equal_1() {
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META3:![0-9]+]])
; CHECK-NEXT: [[R:%.*]] = call i64 @llvm.read_volatile_register.i64(metadata [[META5:![0-9]+]])
; CHECK-NEXT: ret i64 [[R]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_not_equal_2() {
; CHECK-NEXT: [[TMP1:%.*]] = tail call i64 @call_mdtuple_arg_equal_1()
; CHECK-NEXT: ret i64 [[TMP1]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_not_equal_1() {
; CHECK-NEXT: [[TMP1:%.*]] = tail call i64 @call_mdtuple_arg_equal_1()
; CHECK-NEXT: ret i64 [[TMP1]]
;
;
; CHECK-LABEL: define i64 @call_mdtuple_arg_equal_2() {
; CHECK-NEXT: [[TMP1:%.*]] = tail call i64 @call_mdtuple_arg_equal_1()
; CHECK-NEXT: ret i64 [[TMP1]]
;
;.
; CHECK: [[META0]] = distinct !{[[META0]], !"foo"}
; CHECK: [[META1]] = distinct !{[[META1]], !"foo"}
; CHECK: [[META2]] = distinct !{[[META2]], !"bar"}
; CHECK: [[META3]] = !{!"foo", i64 10}
; CHECK: [[META0]] = !{!"foo"}
; CHECK: [[META1]] = !{!"bar"}
; CHECK: [[META2]] = distinct !{[[META2]], !"foo"}
; CHECK: [[META3]] = distinct !{[[META3]], !"foo"}
; CHECK: [[META4]] = distinct !{[[META4]], !"bar"}
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@nikic nikic Feb 26, 2025

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These don't look like valid read_volatile_register arguments? What is your actual motivation here?

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@kubamracek kubamracek Mar 5, 2025

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Actual motivation is to fix something like this...

uintptr_t read_vbar() {
    return __arm_rsr64("VBAR_EL1");
}
uintptr_t read_ttbr0() {
    return __arm_rsr64("TTBR0_EL1");
}

...from miscompiling under -fmerge-functions. See https://godbolt.org/z/qf6zWqzP7.

; CHECK: [[META5]] = !{!"foo", i64 10}
;.
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