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Simplify the computation of undefined symbols. Instead of walking

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functions and initializers, just report the declarations present in
the module.

The motivation is to open the way for using the lazy module parsing,
which should speed up clients that just want a symbol list (nm, ar).

This is slightly less precise, but since both -strip-dead-prototypes
and -globaldce are part of the standard pipeline, this shouldn't
change the result for clang/dragonegg produced binaries.

Any decl in an IL file was also put there because a FE expected it
to be necessary, so this should not be a problem for "-O0 -emit-llvm".

As a sanity check, I have bootstrapped clang on linux and built
firefox on both linux and darwin. A clang bootstrap on darwin
with LTO fails with or without this patch because, ironically,
the linker doesn't like the combination of dead_strip and LTO
when building libLTO.so :-)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127870 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2011-03-18 05:12:38 +00:00
parent 2a72bfa1b1
commit 9a4584b54b
2 changed files with 2 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
tools/lto/LTOModule.cpp
View File

@ -178,16 +178,6 @@ void LTOModule::setTargetTriple(const char *triple) {
void LTOModule::addDefinedFunctionSymbol(Function *f, Mangler &mangler) {
// add to list of defined symbols
addDefinedSymbol(f, mangler, true);
// add external symbols referenced by this function.
for (Function::iterator b = f->begin(); b != f->end(); ++b) {
for (BasicBlock::iterator i = b->begin(); i != b->end(); ++i) {
for (unsigned count = 0, total = i->getNumOperands();
count != total; ++count) {
findExternalRefs(i->getOperand(count), mangler);
}
}
}
}
// Get string that data pointer points to.
@ -328,12 +318,6 @@ void LTOModule::addDefinedDataSymbol(GlobalValue *v, Mangler &mangler) {
}
}
}
// add external symbols referenced by this data.
for (unsigned count = 0, total = v->getNumOperands();
count != total; ++count) {
findExternalRefs(v->getOperand(count), mangler);
}
}
@ -343,10 +327,6 @@ void LTOModule::addDefinedSymbol(GlobalValue *def, Mangler &mangler,
if (def->getName().startswith("llvm."))
return;
// ignore available_externally
if (def->hasAvailableExternallyLinkage())
return;
// string is owned by _defines
SmallString<64> Buffer;
mangler.getNameWithPrefix(Buffer, def, false);
@ -471,28 +451,6 @@ void LTOModule::addPotentialUndefinedSymbol(GlobalValue *decl,
}
// Find external symbols referenced by VALUE. This is a recursive function.
void LTOModule::findExternalRefs(Value *value, Mangler &mangler) {
if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) {
if (!gv->hasExternalLinkage())
addPotentialUndefinedSymbol(gv, mangler);
// If this is a variable definition, do not recursively process
// initializer. It might contain a reference to this variable
// and cause an infinite loop. The initializer will be
// processed in addDefinedDataSymbol().
return;
}
// GlobalValue, even with InternalLinkage type, may have operands with
// ExternalLinkage type. Do not ignore these operands.
if (Constant *c = dyn_cast<Constant>(value)) {
// Handle ConstantExpr, ConstantStruct, ConstantArry etc.
for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i)
findExternalRefs(c->getOperand(i), mangler);
}
}
namespace {
class RecordStreamer : public MCStreamer {
public:
@ -687,7 +645,7 @@ bool LTOModule::ParseSymbols() {
// add functions
for (Module::iterator f = _module->begin(); f != _module->end(); ++f) {
if (f->isDeclaration())
if (f->isDeclaration() || f->hasAvailableExternallyLinkage())
addPotentialUndefinedSymbol(f, mangler);
else
addDefinedFunctionSymbol(f, mangler);
@ -696,7 +654,7 @@ bool LTOModule::ParseSymbols() {
// add data
for (Module::global_iterator v = _module->global_begin(),
e = _module->global_end(); v != e; ++v) {
if (v->isDeclaration())
if (v->isDeclaration() || v->hasAvailableExternallyLinkage())
addPotentialUndefinedSymbol(v, mangler);
else
addDefinedDataSymbol(v, mangler);

2
tools/lto/LTOModule.h
View File

@ -82,8 +82,6 @@ private:
bool isFunction);
void addPotentialUndefinedSymbol(llvm::GlobalValue* decl,
llvm::Mangler &mangler);
void findExternalRefs(llvm::Value* value,
llvm::Mangler& mangler);
void addDefinedFunctionSymbol(llvm::Function* f,
llvm::Mangler &mangler);
void addDefinedDataSymbol(llvm::GlobalValue* v,