[llvm] r265759 - ValueMapper: Treat LocalAsMetadata more like function-local Values
Duncan P. N. Exon Smith via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 7 17:33:45 PDT 2016
Author: dexonsmith
Date: Thu Apr 7 19:33:44 2016
New Revision: 265759
URL: http://llvm.org/viewvc/llvm-project?rev=265759&view=rev
Log:
ValueMapper: Treat LocalAsMetadata more like function-local Values
This is a partial re-commit -- maybe more of a re-implementation -- of
r265631 (reverted in r265637).
This makes RF_IgnoreMissingLocals behave (almost) consistently between
the Value and the Metadata hierarchy. In particular:
- MapValue returns nullptr or "metadata !{}" for missing locals in
MetadataAsValue/LocalAsMetadata bridging paris, depending on
the RF_IgnoreMissingLocals flag.
- MapValue doesn't memoize LocalAsMetadata-related results.
- MapMetadata no longer deals with LocalAsMetadata or
RF_IgnoreMissingLocals at all. (This wasn't in r265631 at all, but
I realized during testing it would make the patch simpler with no
loss of generality.)
r265631 went too far, making both functions universally ignore
RF_IgnoreMissingLocals. This broke building (e.g.) compiler-rt.
Reassociate (and possibly other passes) don't currently maintain
dominates-use invariants for metadata operands, resulting in IR like
this:
define void @foo(i32 %arg) {
call void @llvm.some.intrinsic(metadata i32 %x)
%x = add i32 1, i32 %arg
}
If the inliner chooses to inline @foo into another function, then
RemapInstruction will call `MapValue(metadata i32 %x)` and assert that
the return is not nullptr.
I've filed PR27273 to add a Verifier check and fix the underlying
problem in the optimization passes.
As a workaround, return `!{}` instead of nullptr for unmapped
LocalAsMetadata when RF_IgnoreMissingLocals is unset. Otherwise, match
the behaviour of r265631.
Original commit message:
ValueMapper: Make LocalAsMetadata match function-local Values
Start treating LocalAsMetadata similarly to function-local members of
the Value hierarchy in MapValue and MapMetadata.
- Don't memoize them.
- Return nullptr if they are missing.
This also cleans up ConstantAsMetadata to stop listening to the
RF_IgnoreMissingLocals flag.
Added:
llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/ValueMapper.h
llvm/trunk/lib/IR/Verifier.cpp
llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp
llvm/trunk/unittests/Transforms/Utils/ValueMapperTest.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/ValueMapper.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/ValueMapper.h?rev=265759&r1=265758&r2=265759&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/ValueMapper.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/ValueMapper.h Thu Apr 7 19:33:44 2016
@@ -68,13 +68,21 @@ enum RemapFlags {
RF_NoModuleLevelChanges = 1,
/// If this flag is set, the remapper ignores missing function-local entries
- /// (Argument, Instruction, BasicBlock) that are not in the
- /// value map. If it is unset, it aborts if an operand is asked to be
- /// remapped which doesn't exist in the mapping.
+ /// (Argument, Instruction, BasicBlock) that are not in the value map. If it
+ /// is unset, it aborts if an operand is asked to be remapped which doesn't
+ /// exist in the mapping.
///
- /// There are no such assertions in MapValue(), whose result should be
- /// essentially unchanged by this flag. This only changes the assertion
- /// behaviour in RemapInstruction().
+ /// There are no such assertions in MapValue(), whose results are almost
+ /// unchanged by this flag. This flag mainly changes the assertion behaviour
+ /// in RemapInstruction().
+ ///
+ /// Since an Instruction's metadata operands (even that point to SSA values)
+ /// aren't guaranteed to be dominated by their definitions, MapMetadata will
+ /// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA
+ /// values are unmapped when this flag is set. Otherwise, \a MapValue()
+ /// completely ignores this flag.
+ ///
+ /// \a MapMetadata() always ignores this flag.
RF_IgnoreMissingLocals = 2,
/// Instruct the remapper to move distinct metadata instead of duplicating it
@@ -101,12 +109,32 @@ static inline RemapFlags operator|(Remap
/// 3. Else if \c V is a function-local value, return nullptr.
/// 4. Else if \c V is a \a GlobalValue, return \c nullptr or \c V depending
/// on \a RF_NullMapMissingGlobalValues.
-/// 5. Else, Compute the equivalent constant, and return it.
+/// 5. Else if \c V is a \a MetadataAsValue wrapping a LocalAsMetadata,
+/// recurse on the local SSA value, and return nullptr or "metadata !{}" on
+/// missing depending on RF_IgnoreMissingValues.
+/// 6. Else if \c V is a \a MetadataAsValue, rewrap the return of \a
+/// MapMetadata().
+/// 7. Else, compute the equivalent constant, and return it.
Value *MapValue(const Value *V, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
ValueMaterializer *Materializer = nullptr);
+/// Lookup or compute a mapping for a piece of metadata.
+///
+/// Compute and memoize a mapping for \c MD.
+///
+/// 1. If \c MD is mapped, return it.
+/// 2. Else if \a RF_NoModuleLevelChanges or \c MD is an \a MDString, return
+/// \c MD.
+/// 3. Else if \c MD is a \a ConstantAsMetadata, call \a MapValue() and
+/// re-wrap its return (returning nullptr on nullptr).
+/// 4. Else, \c MD is an \a MDNode. These are remapped, along with their
+/// transitive operands. Distinct nodes are duplicated or moved depending
+/// on \a RF_MoveDistinctNodes. Uniqued nodes are remapped like constants.
+///
+/// \note \a LocalAsMetadata is completely unsupported by \a MapMetadata.
+/// Instead, use \a MapValue() with its wrapping \a MetadataAsValue instance.
Metadata *MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
RemapFlags Flags = RF_None,
ValueMapTypeRemapper *TypeMapper = nullptr,
Modified: llvm/trunk/lib/IR/Verifier.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=265759&r1=265758&r2=265759&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Verifier.cpp (original)
+++ llvm/trunk/lib/IR/Verifier.cpp Thu Apr 7 19:33:44 2016
@@ -3502,6 +3502,10 @@ void Verifier::verifyDominatesUse(Instru
// Quick check whether the def has already been encountered in the same block.
// PHI nodes are not checked to prevent accepting preceeding PHIs, because PHI
// uses are defined to happen on the incoming edge, not at the instruction.
+ //
+ // FIXME: If this operand is a MetadataAsValue (wrapping a LocalAsMetadata)
+ // wrapping an SSA value, assert that we've already encountered it. See
+ // related FIXME in Mapper::mapLocalAsMetadata in ValueMapper.cpp.
if (!isa<PHINode>(I) && InstsInThisBlock.count(Op))
return;
Modified: llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp?rev=265759&r1=265758&r2=265759&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/ValueMapper.cpp Thu Apr 7 19:33:44 2016
@@ -86,6 +86,20 @@ public:
/// (not an MDNode, or MDNode::isResolved() returns true).
Metadata *mapMetadata(const Metadata *MD);
+ // Map LocalAsMetadata, which never gets memoized.
+ //
+ // If the referenced local is not mapped, the principled return is nullptr.
+ // However, optimization passes sometimes move metadata operands *before* the
+ // SSA values they reference. To prevent crashes in \a RemapInstruction(),
+ // return "!{}" when RF_IgnoreMissingLocals is not set.
+ //
+ // \note Adding a mapping for LocalAsMetadata is unsupported. Add a mapping
+ // to the value map for the SSA value in question instead.
+ //
+ // FIXME: Once we have a verifier check for forward references to SSA values
+ // through metadata operands, always return nullptr on unmapped locals.
+ Metadata *mapLocalAsMetadata(const LocalAsMetadata &LAM);
+
private:
Value *mapBlockAddress(const BlockAddress &BA);
@@ -294,18 +308,32 @@ Value *Mapper::mapValue(const Value *V)
if (const auto *MDV = dyn_cast<MetadataAsValue>(V)) {
const Metadata *MD = MDV->getMetadata();
+
+ if (auto *LAM = dyn_cast<LocalAsMetadata>(MD)) {
+ // Look through to grab the local value.
+ if (Value *LV = mapValue(LAM->getValue())) {
+ if (V == LAM->getValue())
+ return const_cast<Value *>(V);
+ return MetadataAsValue::get(V->getContext(), LocalAsMetadata::get(LV));
+ }
+
+ // FIXME: always return nullptr once Verifier::verifyDominatesUse()
+ // ensures metadata operands only reference defined SSA values.
+ return (Flags & RF_IgnoreMissingLocals)
+ ? nullptr
+ : MetadataAsValue::get(V->getContext(),
+ MDTuple::get(V->getContext(), None));
+ }
+
// If this is a module-level metadata and we know that nothing at the module
// level is changing, then use an identity mapping.
- if (!isa<LocalAsMetadata>(MD) && (Flags & RF_NoModuleLevelChanges))
+ if (Flags & RF_NoModuleLevelChanges)
return VM[V] = const_cast<Value *>(V);
- // FIXME: be consistent with function-local values for LocalAsMetadata by
- // returning nullptr when LocalAsMetadata is missing. Adding a mapping is
- // expensive.
+ // Map the metadata and turn it into a value.
auto *MappedMD = mapMetadata(MD);
- if (MD == MappedMD || (!MappedMD && (Flags & RF_IgnoreMissingLocals)))
+ if (MD == MappedMD)
return VM[V] = const_cast<Value *>(V);
-
return VM[V] = MetadataAsValue::get(V->getContext(), MappedMD);
}
@@ -623,21 +651,16 @@ Optional<Metadata *> Mapper::mapSimpleMe
if (isa<MDString>(MD))
return mapToSelf(MD);
- if (isa<ConstantAsMetadata>(MD))
+ if (auto *CMD = dyn_cast<ConstantAsMetadata>(MD)) {
if ((Flags & RF_NoModuleLevelChanges))
return mapToSelf(MD);
- // FIXME: Assert that this is not LocalAsMetadata. It should be handled
- // elsewhere.
- if (const auto *VMD = dyn_cast<ValueAsMetadata>(MD)) {
// Disallow recursion into metadata mapping through mapValue.
VM.disableMapMetadata();
- Value *MappedV = mapValue(VMD->getValue());
+ Value *MappedV = mapValue(CMD->getValue());
VM.enableMapMetadata();
- // FIXME: Always use "ignore" behaviour. There should only be globals here.
- if (VMD->getValue() == MappedV ||
- (!MappedV && (Flags & RF_IgnoreMissingLocals)))
+ if (CMD->getValue() == MappedV)
return mapToSelf(MD);
return mapToMetadata(MD, MappedV ? ValueAsMetadata::get(MappedV) : nullptr);
@@ -659,9 +682,26 @@ Metadata *llvm::MapMetadata(const Metada
return Mapper(VM, Flags, TypeMapper, Materializer).mapMetadata(MD);
}
+Metadata *Mapper::mapLocalAsMetadata(const LocalAsMetadata &LAM) {
+ // Lookup the mapping for the value itself, and return the appropriate
+ // metadata.
+ if (Value *V = mapValue(LAM.getValue())) {
+ if (V == LAM.getValue())
+ return const_cast<LocalAsMetadata *>(&LAM);
+ return ValueAsMetadata::get(V);
+ }
+
+ // FIXME: always return nullptr once Verifier::verifyDominatesUse() ensures
+ // metadata operands only reference defined SSA values.
+ return (Flags & RF_IgnoreMissingLocals)
+ ? nullptr
+ : MDTuple::get(LAM.getContext(), None);
+}
+
Metadata *Mapper::mapMetadata(const Metadata *MD) {
- // FIXME: First check for and deal with LocalAsMetadata, so that
- // mapSimpleMetadata() doesn't need to deal with it.
+ assert(MD && "Expected valid metadata");
+ assert(!isa<LocalAsMetadata>(MD) && "Unexpected local metadata");
+
if (Optional<Metadata *> NewMD = mapSimpleMetadata(MD))
return *NewMD;
Added: llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll?rev=265759&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll (added)
+++ llvm/trunk/test/Transforms/Inline/local-as-metadata-undominated-use.ll Thu Apr 7 19:33:44 2016
@@ -0,0 +1,49 @@
+; RUN: opt -inline -S < %s | FileCheck %s
+
+; Make sure the inliner doesn't crash when a metadata-bridged SSA operand is an
+; undominated use.
+;
+; If we ever add a verifier check to prevent the scenario in this file, it's
+; fine to delete this testcase. However, we would need a bitcode upgrade since
+; such historical IR exists in practice.
+
+define i32 @foo(i32 %i) !dbg !4 {
+entry:
+ tail call void @llvm.dbg.value(metadata i32 %add, i64 0, metadata !8, metadata !10), !dbg !11
+ %add = add nsw i32 1, %i, !dbg !12
+ ret i32 %add, !dbg !13
+}
+
+; CHECK-LABEL: define i32 @caller(
+define i32 @caller(i32 %i) {
+; CHECK-NEXT: entry:
+entry:
+; Although the inliner shouldn't crash, it can't be expected to get the
+; "correct" SSA value since its assumptions have been violated.
+; CHECK-NEXT: tail call void @llvm.dbg.value(metadata ![[EMPTY:[0-9]+]],
+; CHECK-NEXT: %{{.*}} = add nsw
+ %call = tail call i32 @foo(i32 %i)
+ ret i32 %call
+}
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 (trunk 265634) (llvm/trunk 265637)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "t.c", directory: "/path/to/tests")
+
+; CHECK: ![[EMPTY]] = !{}
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true)
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7, !7}
+!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !DILocalVariable(name: "add", arg: 1, scope: !4, file: !1, line: 2, type: !7)
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !DIExpression()
+!11 = !DILocation(line: 2, column: 13, scope: !4)
+!12 = !DILocation(line: 2, column: 27, scope: !4)
+!13 = !DILocation(line: 2, column: 18, scope: !4)
Modified: llvm/trunk/unittests/Transforms/Utils/ValueMapperTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Transforms/Utils/ValueMapperTest.cpp?rev=265759&r1=265758&r2=265759&view=diff
==============================================================================
--- llvm/trunk/unittests/Transforms/Utils/ValueMapperTest.cpp (original)
+++ llvm/trunk/unittests/Transforms/Utils/ValueMapperTest.cpp Thu Apr 7 19:33:44 2016
@@ -139,4 +139,99 @@ TEST(ValueMapperTest, MapMetadataNullMap
EXPECT_EQ(nullptr, MapValue(F.get(), VM, Flags));
}
+TEST(ValueMapperTest, MapMetadataConstantAsMetadata) {
+ LLVMContext C;
+ FunctionType *FTy =
+ FunctionType::get(Type::getVoidTy(C), Type::getInt8Ty(C), false);
+ std::unique_ptr<Function> F(
+ Function::Create(FTy, GlobalValue::ExternalLinkage, "F"));
+
+ auto *CAM = ConstantAsMetadata::get(F.get());
+ {
+ ValueToValueMapTy VM;
+ EXPECT_EQ(CAM, MapMetadata(CAM, VM));
+ EXPECT_TRUE(VM.MD().count(CAM));
+ VM.MD().erase(CAM);
+ EXPECT_EQ(CAM, MapMetadata(CAM, VM, RF_IgnoreMissingLocals));
+ EXPECT_TRUE(VM.MD().count(CAM));
+
+ auto *N = MDTuple::get(C, None);
+ VM.MD()[CAM].reset(N);
+ EXPECT_EQ(N, MapMetadata(CAM, VM));
+ EXPECT_EQ(N, MapMetadata(CAM, VM, RF_IgnoreMissingLocals));
+ }
+
+ std::unique_ptr<Function> F2(
+ Function::Create(FTy, GlobalValue::ExternalLinkage, "F2"));
+ ValueToValueMapTy VM;
+ VM[F.get()] = F2.get();
+ auto *F2MD = MapMetadata(CAM, VM);
+ EXPECT_TRUE(VM.MD().count(CAM));
+ EXPECT_TRUE(F2MD);
+ EXPECT_EQ(F2.get(), cast<ConstantAsMetadata>(F2MD)->getValue());
+}
+
+#ifdef GTEST_HAS_DEATH_TEST
+#ifndef NDEBUG
+TEST(ValueMapperTest, MapMetadataLocalAsMetadata) {
+ LLVMContext C;
+ FunctionType *FTy =
+ FunctionType::get(Type::getVoidTy(C), Type::getInt8Ty(C), false);
+ std::unique_ptr<Function> F(
+ Function::Create(FTy, GlobalValue::ExternalLinkage, "F"));
+ Argument &A = *F->arg_begin();
+
+ // MapMetadata doesn't support LocalAsMetadata. The only valid container for
+ // LocalAsMetadata is a MetadataAsValue instance, so use it directly.
+ auto *LAM = LocalAsMetadata::get(&A);
+ ValueToValueMapTy VM;
+ EXPECT_DEATH(MapMetadata(LAM, VM), "Unexpected local metadata");
+ EXPECT_DEATH(MapMetadata(LAM, VM, RF_IgnoreMissingLocals),
+ "Unexpected local metadata");
+}
+#endif
+#endif
+
+TEST(ValueMapperTest, MapValueLocalAsMetadata) {
+ LLVMContext C;
+ FunctionType *FTy =
+ FunctionType::get(Type::getVoidTy(C), Type::getInt8Ty(C), false);
+ std::unique_ptr<Function> F(
+ Function::Create(FTy, GlobalValue::ExternalLinkage, "F"));
+ Argument &A = *F->arg_begin();
+
+ auto *LAM = LocalAsMetadata::get(&A);
+ auto *MAV = MetadataAsValue::get(C, LAM);
+
+ // The principled answer to a LocalAsMetadata of an unmapped SSA value would
+ // be to return nullptr (regardless of RF_IgnoreMissingLocals).
+ //
+ // However, algorithms that use RemapInstruction assume that each instruction
+ // only references SSA values from previous instructions. Arguments of
+ // such as "metadata i32 %x" don't currently successfully maintain that
+ // property. To keep RemapInstruction from crashing we need a non-null
+ // return here, but we also shouldn't reference the unmapped local. Use
+ // "metadata !{}".
+ auto *N0 = MDTuple::get(C, None);
+ auto *N0AV = MetadataAsValue::get(C, N0);
+ ValueToValueMapTy VM;
+ EXPECT_EQ(N0AV, MapValue(MAV, VM));
+ EXPECT_EQ(nullptr, MapValue(MAV, VM, RF_IgnoreMissingLocals));
+ EXPECT_FALSE(VM.count(MAV));
+ EXPECT_FALSE(VM.count(&A));
+ EXPECT_EQ(None, VM.getMappedMD(LAM));
+
+ VM[MAV] = MAV;
+ EXPECT_EQ(MAV, MapValue(MAV, VM));
+ EXPECT_EQ(MAV, MapValue(MAV, VM, RF_IgnoreMissingLocals));
+ EXPECT_TRUE(VM.count(MAV));
+ EXPECT_FALSE(VM.count(&A));
+
+ VM[MAV] = &A;
+ EXPECT_EQ(&A, MapValue(MAV, VM));
+ EXPECT_EQ(&A, MapValue(MAV, VM, RF_IgnoreMissingLocals));
+ EXPECT_TRUE(VM.count(MAV));
+ EXPECT_FALSE(VM.count(&A));
+}
+
} // end namespace
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