<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Thanks for the feedback. Comments below, based on r239429 which i just pushed.<br class=""><div><blockquote type="cite" class=""><div class="">On Jun 9, 2015, at 1:10 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" class="">dblaikie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Tue, Jun 9, 2015 at 12:56 PM, Pete Cooper <span dir="ltr" class=""><<a href="mailto:peter_cooper@apple.com" target="_blank" class="">peter_cooper@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: pete<br class="">
Date: Tue Jun 9 14:56:05 2015<br class="">
New Revision: 239428<br class="">
<br class="">
URL: <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D239428-26view-3Drev&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=lFVHjF04pzv2_EGqkeUP69GAvZ85oGItRAEzkq4ePmM&s=IsDMivchm_YHkRi64f5BbsKt2kSNscrNI-VFxAKjrqY&e=" target="_blank" class="">http://llvm.org/viewvc/llvm-project?rev=239428&view=rev</a><br class="">
Log:<br class="">
Make MCSymbol::Name be a union of uint64_t and a pointer.<br class="">
<br class="">
This should hopefully fix the 32-bit bots which were allocating space for a pointer<br class="">
but needed to be aligned to 64-bits.<br class="">
<br class="">
Now we allocate enough space for a uint64_t and a pointer and cast to the appropriate storage<br class=""></blockquote><div class=""><br class="">This kind fo complicates the rest of the MCSymbol code. A few options:<br class=""><br class="">have getNameEntry return the NameEntry reference as before (do the ".NameEntry" inside getNameEntry rather than in both the callers).<br class=""></div></div></div></div></div></blockquote>This is done.<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><br class="">Possibly just do the interesting uint64_t stuff inside operator new - though I suppose you'd still need some magic in getNameEntry that would look similar.<br class=""></div></div></div></div></div></blockquote>I thought about this, but because it was handled in getNameEntry() too, I went for the union solution so that at least everything is based on the union size and storage.<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><br class="">& the alignment assertion could probably be a static_assert? (might need to check if alignOf is constexpr or if we have a trait/constexpr form of it)<br class=""></div></div></div></div></div></blockquote>Turns out constexpr is still not used much in LLVM. We have a macro for it. I guess MSVC doesn’t support it fully on our version. I’ve added a FIXME so that we can handle this later.<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""><br class=""><br class="">Oh, side note (should've caught this in review): you could have getNameEntry non-const call getNameEntry const and just cast away the constness on the resulting reference - to reduce some of that code duplication.<br class=""></div></div></div></div></div></blockquote>I’ve done this. I had to cast away the const-ness and make the const method call the non-const one. This was due to the const-ness of the result. Basically, this solution is a single const_cast, but the other way would have been 2.</div><div><br class=""></div><div>Thanks for the help!</div><div>Pete<br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><div class=""> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br class="">
Modified:<br class="">
llvm/trunk/include/llvm/MC/MCSymbol.h<br class="">
llvm/trunk/lib/MC/MCSymbol.cpp<br class="">
<br class="">
Modified: llvm/trunk/include/llvm/MC/MCSymbol.h<br class="">
URL: <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_include_llvm_MC_MCSymbol.h-3Frev-3D239428-26r1-3D239427-26r2-3D239428-26view-3Ddiff&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=lFVHjF04pzv2_EGqkeUP69GAvZ85oGItRAEzkq4ePmM&s=ZCocnXsfmoi2Qw4MlKOURuuHUqJlebQR_b0eX4UMZCo&e=" target="_blank" class="">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSymbol.h?rev=239428&r1=239427&r2=239428&view=diff</a><br class="">
==============================================================================<br class="">
--- llvm/trunk/include/llvm/MC/MCSymbol.h (original)<br class="">
+++ llvm/trunk/include/llvm/MC/MCSymbol.h Tue Jun 9 14:56:05 2015<br class="">
@@ -120,20 +120,29 @@ protected: // MCContext creates and uniq<br class="">
friend class MCExpr;<br class="">
friend class MCContext;<br class="">
<br class="">
- typedef const StringMapEntry<bool> NameEntryTy;<br class="">
- MCSymbol(SymbolKind Kind, NameEntryTy *Name, bool isTemporary)<br class="">
+ /// \brief The name for a symbol.<br class="">
+ /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit<br class="">
+ /// system, the name is a pointer so isn't going to satisfy the 8 byte<br class="">
+ /// alignment of uint64_t. Account for that here.<br class="">
+ typedef union {<br class="">
+ const StringMapEntry<bool> *NameEntry;<br class="">
+ uint64_t AlignmentPadding;<br class="">
+ } NameEntryStorageTy;<br class="">
+<br class="">
+ MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)<br class="">
: Value(nullptr), IsTemporary(isTemporary),<br class="">
IsRedefinable(false), IsUsed(false), IsRegistered(false),<br class="">
IsExternal(false), IsPrivateExtern(false), HasName(!!Name),<br class="">
Kind(Kind) {<br class="">
Offset = 0;<br class="">
if (Name)<br class="">
- getNameEntryPtr() = Name;<br class="">
+ getNameEntryPtr().NameEntry = Name;<br class="">
}<br class="">
<br class="">
// Provide custom new/delete as we will only allocate space for a name<br class="">
// if we need one.<br class="">
- void *operator new(size_t s, NameEntryTy *Name, MCContext &Ctx);<br class="">
+ void *operator new(size_t s, const StringMapEntry<bool> *Name,<br class="">
+ MCContext &Ctx);<br class="">
<br class="">
private:<br class="">
<br class="">
@@ -160,14 +169,14 @@ private:<br class="">
}<br class="">
<br class="">
/// \brief Get a reference to the name field. Requires that we have a name<br class="">
- NameEntryTy *&getNameEntryPtr() {<br class="">
+ NameEntryStorageTy &getNameEntryPtr() {<br class="">
assert(HasName && "Name is required");<br class="">
- NameEntryTy **Name = reinterpret_cast<NameEntryTy **>(this);<br class="">
+ NameEntryStorageTy *Name = reinterpret_cast<NameEntryStorageTy *>(this);<br class="">
return *(Name - 1);<br class="">
}<br class="">
- NameEntryTy *const &getNameEntryPtr() const {<br class="">
+ const NameEntryStorageTy &getNameEntryPtr() const {<br class="">
assert(HasName && "Name is required");<br class="">
- NameEntryTy *const *Name = reinterpret_cast<NameEntryTy *const *>(this);<br class="">
+ const auto *Name = reinterpret_cast<const NameEntryStorageTy *>(this);<br class="">
return *(Name - 1);<br class="">
}<br class="">
<br class="">
@@ -177,7 +186,7 @@ public:<br class="">
if (!HasName)<br class="">
return StringRef();<br class="">
<br class="">
- return getNameEntryPtr()->first();<br class="">
+ return getNameEntryPtr().NameEntry->first();<br class="">
}<br class="">
<br class="">
bool isRegistered() const { return IsRegistered; }<br class="">
<br class="">
Modified: llvm/trunk/lib/MC/MCSymbol.cpp<br class="">
URL: <a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_llvm_trunk_lib_MC_MCSymbol.cpp-3Frev-3D239428-26r1-3D239427-26r2-3D239428-26view-3Ddiff&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=lFVHjF04pzv2_EGqkeUP69GAvZ85oGItRAEzkq4ePmM&s=HzIY0tLNsmE1cQV-RM-CxuTQWGCZYuCTDBJQlF_86vE&e=" target="_blank" class="">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCSymbol.cpp?rev=239428&r1=239427&r2=239428&view=diff</a><br class="">
==============================================================================<br class="">
--- llvm/trunk/lib/MC/MCSymbol.cpp (original)<br class="">
+++ llvm/trunk/lib/MC/MCSymbol.cpp Tue Jun 9 14:56:05 2015<br class="">
@@ -19,17 +19,20 @@ using namespace llvm;<br class="">
// Sentinel value for the absolute pseudo section.<br class="">
MCSection *MCSymbol::AbsolutePseudoSection = reinterpret_cast<MCSection *>(1);<br class="">
<br class="">
-void *MCSymbol::operator new(size_t s, NameEntryTy *Name, MCContext &Ctx) {<br class="">
- size_t Size = s + (Name ? sizeof(Name) : 0);<br class="">
+void *MCSymbol::operator new(size_t s, const StringMapEntry<bool> *Name,<br class="">
+ MCContext &Ctx) {<br class="">
+ // We may need more space for a Name to account for alignment. So allocate<br class="">
+ // space for the storage type and not the name pointer.<br class="">
+ size_t Size = s + (Name ? sizeof(NameEntryStorageTy) : 0);<br class="">
<br class="">
// For safety, ensure that the alignment of a pointer is enough for an<br class="">
// MCSymbol. This also ensures we don't need padding between the name and<br class="">
// symbol.<br class="">
- assert(alignOf<MCSymbol>() <= alignOf<NameEntryTy *>() &&<br class="">
+ assert(alignOf<MCSymbol>() <= alignOf<NameEntryStorageTy>() &&<br class="">
"Bad alignment of MCSymbol");<br class="">
- void *Storage = Ctx.allocate(Size, alignOf<NameEntryTy *>());<br class="">
- NameEntryTy **Start = static_cast<NameEntryTy**>(Storage);<br class="">
- NameEntryTy **End = Start + (Name ? 1 : 0);<br class="">
+ void *Storage = Ctx.allocate(Size, alignOf<NameEntryStorageTy>());<br class="">
+ NameEntryStorageTy *Start = static_cast<NameEntryStorageTy*>(Storage);<br class="">
+ NameEntryStorageTy *End = Start + (Name ? 1 : 0);<br class="">
return End;<br class="">
}<br class="">
<br class="">
<br class="">
<br class="">
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