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Reapply "AsmPrinter: Change DIEValue to be stored by value"

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This reverts commit r238350, effectively reapplying r238349 after fixing
(all?) the problems, all somehow related to how I was using
`AlignedArrayCharUnion<>` inside `DIEValue`:

  - MSVC can only handle `sizeof()` on types, not values.  Change the
    assert.
  - GCC doesn't know the `is_trivially_copyable` type trait.  Instead of
    asserting it, add destructors.
  - Call placement new even when constructing POD (i.e., the pointers).
  - Instead of copying the char buffer, copy the casted classes.

I've left in a couple of `static_assert`s that I think both MSVC and GCC
know how to handle.  If the bots disagree with me, I'll remove them.

  - Check that the constructed type is either standard layout or a
    pointer.  This protects against a programming error: we really want
    the "small" `DIEValue`s to be small and simple, so don't
    accidentally change them not to be.
  - Similarly, check that the size of the buffer is no bigger than a
    `uint64_t` or a pointer.  (I thought checking against
    `sizeof(uint64_t)` would be good enough, but Chandler suggested that
    pointers might sometimes be bigger than that in the context of
    sanitizers.)

I've also committed r238359 in the meantime, which introduces a
DIEValue.def to simplify dispatching between the various types (thanks
to a review comment by David Blaikie).  Without that, this commit would
be almost unintelligible.

Here's the original commit message:
--
Change `DIEValue` to be stored/passed/etc. by value, instead of
reference.  It's now a discriminated union, with a `Val` field storing
the actual type.  The classes that used to inherit from `DIEValue` no
longer do.  There are two categories of these:

  - Small values fit in a single pointer and are stored by value.
  - Large values require auxiliary storage, and are stored by reference.

The only non-mechanical change is to tools/dsymutil/DwarfLinker.cpp.  It
was relying on `DIEInteger`s being passed around by reference, so I
replaced that assumption with a `PatchLocation` type that stores a safe
reference to where the `DIEInteger` lives instead.

This commit causes a temporary regression in memory usage, since I've
left merging `DIEAbbrevData` into `DIEValue` for a follow-up commit.  I
measured an increase from 845 MB to 879 MB, around 3.9%.  The follow-up
drops it lower than the starting point, and I've only recently brought
the memory this low anyway, so I'm committing these changes separately
to keep them incremental.  (I also considered swapping the commits, but
the other one first would cause a lot more code churn.)

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)
--

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238362 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2015-05-27 22:14:58 +00:00
parent 344593ce6c
commit 09fe4bf794
13 changed files with 577 additions and 547 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
lib/CodeGen/AsmPrinter/DIEHash.cpp
View File

@ -31,18 +31,14 @@ using namespace llvm;
/// \brief Grabs the string in whichever attribute is passed in and returns
/// a reference to it.
static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr) {
const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
const auto &Values = Die.getValues();
const DIEAbbrev &Abbrevs = Die.getAbbrev();
// Iterate through all the attributes until we find the one we're
// looking for, if we can't find it return an empty string.
for (size_t i = 0; i < Values.size(); ++i) {
if (Abbrevs.getData()[i].getAttribute() == Attr) {
DIEValue *V = Values[i];
assert(isa<DIEString>(V) && "String requested. Not a string.");
DIEString *S = cast<DIEString>(V);
return S->getString();
}
if (Abbrevs.getData()[i].getAttribute() == Attr)
return Values[i].getDIEString().getString();
}
return StringRef("");
}
@ -123,7 +119,7 @@ void DIEHash::addParentContext(const DIE &Parent) {
// Collect all of the attributes for a particular DIE in single structure.
void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) {
const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
const SmallVectorImpl<DIEValue> &Values = Die.getValues();
const DIEAbbrev &Abbrevs = Die.getAbbrev();
#define COLLECT_ATTR(NAME) \
@ -274,11 +270,9 @@ void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag,
// Hash all of the values in a block like set of values. This assumes that
// all of the data is going to be added as integers.
void DIEHash::hashBlockData(const SmallVectorImpl<DIEValue *> &Values) {
for (SmallVectorImpl<DIEValue *>::const_iterator I = Values.begin(),
E = Values.end();
I != E; ++I)
Hash.update((uint64_t)cast<DIEInteger>(*I)->getValue());
void DIEHash::hashBlockData(const SmallVectorImpl<DIEValue> &Values) {
for (auto I = Values.begin(), E = Values.end(); I != E; ++I)
Hash.update((uint64_t)I->getDIEInteger().getValue());
}
// Hash the contents of a loclistptr class.
@ -293,7 +287,7 @@ void DIEHash::hashLocList(const DIELocList &LocList) {
// Hash an individual attribute \param Attr based on the type of attribute and
// the form.
void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
const DIEValue *Value = Attr.Val;
const DIEValue &Value = Attr.Val;
const DIEAbbrevData *Desc = Attr.Desc;
dwarf::Attribute Attribute = Desc->getAttribute();
@ -304,12 +298,15 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
// computation is limited to the following: DW_FORM_sdata, DW_FORM_flag,
// DW_FORM_string, and DW_FORM_block.
switch (Value->getType()) {
switch (Value.getType()) {
case DIEValue::isNone:
llvm_unreachable("Expected valid DIEValue");
// 7.27 Step 3
// ... An attribute that refers to another type entry T is processed as
// follows:
case DIEValue::isEntry:
hashDIEEntry(Attribute, Tag, cast<DIEEntry>(Value)->getEntry());
hashDIEEntry(Attribute, Tag, Value.getDIEEntry().getEntry());
break;
case DIEValue::isInteger: {
addULEB128('A');
@ -322,14 +319,14 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
case dwarf::DW_FORM_udata:
case dwarf::DW_FORM_sdata:
addULEB128(dwarf::DW_FORM_sdata);
addSLEB128((int64_t)cast<DIEInteger>(Value)->getValue());
addSLEB128((int64_t)Value.getDIEInteger().getValue());
break;
// DW_FORM_flag_present is just flag with a value of one. We still give it a
// value so just use the value.
case dwarf::DW_FORM_flag_present:
case dwarf::DW_FORM_flag:
addULEB128(dwarf::DW_FORM_flag);
addULEB128((int64_t)cast<DIEInteger>(Value)->getValue());
addULEB128((int64_t)Value.getDIEInteger().getValue());
break;
default:
llvm_unreachable("Unknown integer form!");
@ -340,7 +337,7 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
addULEB128('A');
addULEB128(Attribute);
addULEB128(dwarf::DW_FORM_string);
addString(cast<DIEString>(Value)->getString());
addString(Value.getDIEString().getString());
break;
case DIEValue::isBlock:
case DIEValue::isLoc:
@ -348,17 +345,17 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
addULEB128('A');
addULEB128(Attribute);
addULEB128(dwarf::DW_FORM_block);
if (isa<DIEBlock>(Value)) {
addULEB128(cast<DIEBlock>(Value)->ComputeSize(AP));
hashBlockData(cast<DIEBlock>(Value)->getValues());
} else if (isa<DIELoc>(Value)) {
addULEB128(cast<DIELoc>(Value)->ComputeSize(AP));
hashBlockData(cast<DIELoc>(Value)->getValues());
if (Value.getType() == DIEValue::isBlock) {
addULEB128(Value.getDIEBlock().ComputeSize(AP));
hashBlockData(Value.getDIEBlock().getValues());
} else if (Value.getType() == DIEValue::isLoc) {
addULEB128(Value.getDIELoc().ComputeSize(AP));
hashBlockData(Value.getDIELoc().getValues());
} else {
// We could add the block length, but that would take
// a bit of work and not add a lot of uniqueness
// to the hash in some way we could test.
hashLocList(*cast<DIELocList>(Value));
hashLocList(Value.getDIELocList());
}
break;
// FIXME: It's uncertain whether or not we should handle this at the moment.
@ -375,7 +372,7 @@ void DIEHash::hashAttribute(AttrEntry Attr, dwarf::Tag Tag) {
void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) {
#define ADD_ATTR(ATTR) \
{ \
if (ATTR.Val != 0) \
if (ATTR.Val) \
hashAttribute(ATTR, Tag); \
}