<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Nov 13, 2014 at 5:17 PM, Duncan P. N. Exon Smith <span dir="ltr"><<a href="mailto:dexonsmith@apple.com" target="_blank">dexonsmith@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: dexonsmith<br>
Date: Thu Nov 13 19:17:09 2014<br>
New Revision: 221960<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=221960&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=221960&view=rev</a><br>
Log:<br>
IR: Rewrite uniquing and creation of MDString<br>
<br>
Stop using `Value::getName()` to get the string behind an `MDString`.<br>
Switch to `StringMapEntry<MDString>` so that we can find the string by<br>
its coallocation.<br>
<br>
This is part of PR21532.<br>
<br>
Modified:<br>
llvm/trunk/include/llvm/IR/Metadata.h<br>
llvm/trunk/lib/IR/LLVMContextImpl.cpp<br>
llvm/trunk/lib/IR/LLVMContextImpl.h<br>
llvm/trunk/lib/IR/Metadata.cpp<br>
<br>
Modified: llvm/trunk/include/llvm/IR/Metadata.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Metadata.h?rev=221960&r1=221959&r2=221960&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Metadata.h?rev=221960&r1=221959&r2=221960&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/IR/Metadata.h (original)<br>
+++ llvm/trunk/include/llvm/IR/Metadata.h Thu Nov 13 19:17:09 2014<br>
@@ -57,14 +57,15 @@ public:<br>
///<br>
/// TODO: Inherit from Metadata.<br>
class MDString : public Value {<br>
+ friend class StringMapEntry<MDString>;<br></blockquote><div><br>This seems annoyingly tied to the implementation details of StringMap (exactly where in the stack the constructor is called, etc)... I wonder if there's a better answer, but none springs immediately to mind.<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+<br>
virtual void anchor();<br>
MDString(const MDString &) LLVM_DELETED_FUNCTION;<br>
<br>
explicit MDString(LLVMContext &C);<br>
<br>
-private:<br>
/// \brief Shadow Value::getName() to prevent its use.<br>
- StringRef getName() const { return Value::getName(); }<br>
+ StringRef getName() const LLVM_DELETED_FUNCTION;<br>
<br>
public:<br>
static MDString *get(LLVMContext &Context, StringRef Str);<br>
@@ -72,17 +73,17 @@ public:<br>
return get(Context, Str ? StringRef(Str) : StringRef());<br>
}<br>
<br>
- StringRef getString() const { return getName(); }<br>
+ StringRef getString() const;<br>
<br>
- unsigned getLength() const { return (unsigned)getName().size(); }<br>
+ unsigned getLength() const { return (unsigned)getString().size(); }<br>
<br>
typedef StringRef::iterator iterator;<br>
<br>
/// \brief Pointer to the first byte of the string.<br>
- iterator begin() const { return getName().begin(); }<br>
+ iterator begin() const { return getString().begin(); }<br>
<br>
/// \brief Pointer to one byte past the end of the string.<br>
- iterator end() const { return getName().end(); }<br>
+ iterator end() const { return getString().end(); }<br>
<br>
/// \brief Methods for support type inquiry through isa, cast, and dyn_cast.<br>
static bool classof(const Value *V) {<br>
<br>
Modified: llvm/trunk/lib/IR/LLVMContextImpl.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/LLVMContextImpl.cpp?rev=221960&r1=221959&r2=221960&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/LLVMContextImpl.cpp?rev=221960&r1=221959&r2=221960&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/IR/LLVMContextImpl.cpp (original)<br>
+++ llvm/trunk/lib/IR/LLVMContextImpl.cpp Thu Nov 13 19:17:09 2014<br>
@@ -135,7 +135,7 @@ LLVMContextImpl::~LLVMContextImpl() {<br>
"Destroying all MDNodes didn't empty the Context's sets.");<br>
<br>
// Destroy MDStrings.<br>
- DeleteContainerSeconds(MDStringCache);<br>
+ MDStringCache.clear();<br>
}<br>
<br>
// ConstantsContext anchors<br>
<br>
Modified: llvm/trunk/lib/IR/LLVMContextImpl.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/LLVMContextImpl.h?rev=221960&r1=221959&r2=221960&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/LLVMContextImpl.h?rev=221960&r1=221959&r2=221960&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/IR/LLVMContextImpl.h (original)<br>
+++ llvm/trunk/lib/IR/LLVMContextImpl.h Thu Nov 13 19:17:09 2014<br>
@@ -261,7 +261,7 @@ public:<br>
FoldingSet<AttributeSetImpl> AttrsLists;<br>
FoldingSet<AttributeSetNode> AttrsSetNodes;<br>
<br>
- StringMap<Value*> MDStringCache;<br>
+ StringMap<MDString> MDStringCache;<br>
<br>
FoldingSet<MDNode> MDNodeSet;<br>
<br>
<br>
Modified: llvm/trunk/lib/IR/Metadata.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Metadata.cpp?rev=221960&r1=221959&r2=221960&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Metadata.cpp?rev=221960&r1=221959&r2=221960&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/IR/Metadata.cpp (original)<br>
+++ llvm/trunk/lib/IR/Metadata.cpp Thu Nov 13 19:17:09 2014<br>
@@ -37,13 +37,21 @@ MDString::MDString(LLVMContext &C)<br>
: Value(Type::getMetadataTy(C), Value::MDStringVal) {}<br>
<br>
MDString *MDString::get(LLVMContext &Context, StringRef Str) {<br>
- LLVMContextImpl *pImpl = Context.pImpl;<br>
- StringMapEntry<Value*> &Entry =<br>
- pImpl->MDStringCache.GetOrCreateValue(Str);<br>
- Value *&S = Entry.getValue();<br>
- if (!S) S = new MDString(Context);<br>
- S->setValueName(&Entry);<br>
- return cast<MDString>(S);<br>
+ auto &Store = Context.pImpl->MDStringCache;<br>
+ auto I = Store.find(Str);<br>
+ if (I != Store.end())<br>
+ return &I->second;<br>
+<br>
+ auto *Entry =<br>
+ StringMapEntry<MDString>::Create(Str, Store.getAllocator(), Context);<br></blockquote><div><br>This seems like it's the wrong API design - forwarding a single argument and calling an explicit constructor doesn't seem right. APIs (such as push_back) generally do perfect forwarding of a single argument where the argument is implicitly convertible to the underlying type, but not for explicit conversions. <br><br>For explicit conversions the idiom seems to be to have an 'emplace' function.<br><br>I think the right API design is to add an 'emplace' to StringMap and use it something like this:<br><br>Store.insert(std::piecewise_construct, std::forward_as_tuple(Str), std::forward_as_tuple(Context));<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+ bool WasInserted = Store.insert(Entry);<br>
+ (void)WasInserted;<br>
+ assert(WasInserted && "Expected entry to be inserted");<br>
+ return &Entry->second;<br>
+}<br>
+<br>
+StringRef MDString::getString() const {<br>
+ return StringMapEntry<MDString>::GetStringMapEntryFromValue(*this).first();<br>
}<br>
<br>
//===----------------------------------------------------------------------===//<br>
<br>
<br>
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</blockquote></div><br></div></div>