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ValueMapper: Stop memoizing ConstantAsMetadata

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Stop memoizing ConstantAsMetadata in ValueMapper::mapMetadata.  Now we
have to recompute it, but these metadata aren't particularly common, and
it restricts the lifetime of the Metadata map unnecessarily.

(The motivation is that I have a patch which uses a single Metadata map
for the lifetime of IRMover.  Mehdi profiled r266446 with the patch
applied and we saw a pretty big speedup in lib/Linker.)

llvm-svn: 266513
This commit is contained in:
Duncan P. N. Exon Smith 2016-04-16 03:39:44 +00:00
parent 3c07e94e4f
commit a4defb35fe
2 changed files with 41 additions and 13 deletions
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45
lib/Transforms/Utils/ValueMapper.cpp
View File

@ -505,14 +505,26 @@ bool MDNodeMapper::mapOperand(const Metadata *Op) {
return false;
if (Optional<Metadata *> MappedOp = M.mapSimpleMetadata(Op)) {
assert((isa<MDString>(Op) || M.getVM().getMappedMD(Op)) &&
"Expected result to be memoized");
if (auto *CMD = dyn_cast<ConstantAsMetadata>(Op))
assert((!*MappedOp || M.getVM().count(CMD->getValue()) ||
M.getVM().getMappedMD(Op)) &&
"Expected Value to be memoized");
else
assert((isa<MDString>(Op) || M.getVM().getMappedMD(Op)) &&
"Expected result to be memoized");
return *MappedOp != Op;
}
return push(*cast<MDNode>(Op)).HasChangedAddress;
}
static ConstantAsMetadata *wrapConstantAsMetadata(const ConstantAsMetadata &CMD,
Value *MappedV) {
if (CMD.getValue() == MappedV)
return const_cast<ConstantAsMetadata *>(&CMD);
return MappedV ? ConstantAsMetadata::getConstant(MappedV) : nullptr;
}
Optional<Metadata *> MDNodeMapper::getMappedOp(const Metadata *Op) const {
if (!Op)
return nullptr;
@ -523,6 +535,9 @@ Optional<Metadata *> MDNodeMapper::getMappedOp(const Metadata *Op) const {
if (isa<MDString>(Op))
return const_cast<Metadata *>(Op);
if (auto *CMD = dyn_cast<ConstantAsMetadata>(Op))
return wrapConstantAsMetadata(*CMD, M.getVM().lookup(CMD->getValue()));
return None;
}
@ -720,6 +735,19 @@ Metadata *MDNodeMapper::map(const MDNode &FirstN) {
return *getMappedOp(&FirstN);
}
namespace {
struct MapMetadataDisabler {
ValueToValueMapTy &VM;
MapMetadataDisabler(ValueToValueMapTy &VM) : VM(VM) {
VM.disableMapMetadata();
}
~MapMetadataDisabler() { VM.enableMapMetadata(); }
};
} // end namespace
Optional<Metadata *> Mapper::mapSimpleMetadata(const Metadata *MD) {
// If the value already exists in the map, use it.
if (Optional<Metadata *> NewMD = getVM().getMappedMD(MD))
@ -735,14 +763,13 @@ Optional<Metadata *> Mapper::mapSimpleMetadata(const Metadata *MD) {
if (auto *CMD = dyn_cast<ConstantAsMetadata>(MD)) {
// Disallow recursion into metadata mapping through mapValue.
getVM().disableMapMetadata();
Value *MappedV = mapValue(CMD->getValue());
getVM().enableMapMetadata();
MapMetadataDisabler MMD(getVM());
if (CMD->getValue() == MappedV)
return mapToSelf(MD);
return mapToMetadata(MD, MappedV ? ValueAsMetadata::get(MappedV) : nullptr);
// Don't memoize ConstantAsMetadata. Instead of lasting until the
// LLVMContext is destroyed, they can be deleted when the GlobalValue they
// reference is destructed. These aren't super common, so the extra
// indirection isn't that expensive.
return wrapConstantAsMetadata(*CMD, mapValue(CMD->getValue()));
}
assert(isa<MDNode>(MD) && "Expected a metadata node");

9
unittests/Transforms/Utils/ValueMapperTest.cpp
View File

@ -238,13 +238,14 @@ TEST(ValueMapperTest, mapMetadataConstantAsMetadata) {
auto *CAM = ConstantAsMetadata::get(F.get());
{
// ConstantAsMetadata shouldn't be memoized.
ValueToValueMapTy VM;
EXPECT_EQ(CAM, ValueMapper(VM).mapMetadata(*CAM));
EXPECT_TRUE(VM.MD().count(CAM));
VM.MD().erase(CAM);
EXPECT_FALSE(VM.MD().count(CAM));
EXPECT_EQ(CAM, ValueMapper(VM, RF_IgnoreMissingLocals).mapMetadata(*CAM));
EXPECT_TRUE(VM.MD().count(CAM));
EXPECT_FALSE(VM.MD().count(CAM));
// But it should respect a mapping that gets seeded.
auto *N = MDTuple::get(C, None);
VM.MD()[CAM].reset(N);
EXPECT_EQ(N, ValueMapper(VM).mapMetadata(*CAM));
@ -256,7 +257,7 @@ TEST(ValueMapperTest, mapMetadataConstantAsMetadata) {
ValueToValueMapTy VM;
VM[F.get()] = F2.get();
auto *F2MD = ValueMapper(VM).mapMetadata(*CAM);
EXPECT_TRUE(VM.MD().count(CAM));
EXPECT_FALSE(VM.MD().count(CAM));
EXPECT_TRUE(F2MD);
EXPECT_EQ(F2.get(), cast<ConstantAsMetadata>(F2MD)->getValue());
}