nicolas/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Handle and warn on aliases to weak aliases.

Browse Source 
This produces valid IR now that llvm rejects aliases to weak aliases and warns
the user that the resolution is not changed if the weak alias is overridden.

llvm-svn: 204935
This commit is contained in:
Rafael Espindola
2014-03-27 15:27:20 +00:00
parent 24a669d225
commit a39fc6dd2a
4 changed files with 42 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
clang/lib/CodeGen/CodeGenModule.cpp
View File

@@ -208,6 +208,9 @@ void CodeGenModule::applyReplacements() {
}
void CodeGenModule::checkAliases() {
// Check if the constructed aliases are well formed. It is really unfortunate
// that we have to do this in CodeGen, but we only construct mangled names
// and aliases during codegen.
bool Error = false;
for (std::vector<GlobalDecl>::iterator I = Aliases.begin(),
E = Aliases.end(); I != E; ++I) {
@@ -217,7 +220,7 @@ void CodeGenModule::checkAliases() {
StringRef MangledName = getMangledName(GD);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
llvm::GlobalAlias *Alias = cast<llvm::GlobalAlias>(Entry);
llvm::GlobalValue *GV = Alias->resolveAliasedGlobal(/*stopOnWeak*/ false);
llvm::GlobalValue *GV = Alias->getAliasedGlobal();
if (!GV) {
Error = true;
getDiags().Report(AA->getLocation(), diag::err_cyclic_alias);
@@ -225,6 +228,31 @@ void CodeGenModule::checkAliases() {
Error = true;
getDiags().Report(AA->getLocation(), diag::err_alias_to_undefined);
}
// We have to handle alias to weak aliases in here. LLVM itself disallows
// this since the object semantics would not match the IL one. For
// compatibility with gcc we implement it by just pointing the alias
// to its aliasee's aliasee. We also warn, since the user is probably
// expecting the link to be weak.
llvm::Constant *Aliasee = Alias->getAliasee();
llvm::GlobalValue *AliaseeGV;
if (auto CE = dyn_cast<llvm::ConstantExpr>(Aliasee)) {
assert((CE->getOpcode() == llvm::Instruction::BitCast ||
CE->getOpcode() == llvm::Instruction::AddrSpaceCast) &&
"Unsupported aliasee");
AliaseeGV = cast<llvm::GlobalValue>(CE->getOperand(0));
} else {
AliaseeGV = cast<llvm::GlobalValue>(Aliasee);
}
if (auto GA = dyn_cast<llvm::GlobalAlias>(AliaseeGV)) {
if (GA->mayBeOverridden()) {
getDiags().Report(AA->getLocation(), diag::warn_alias_to_weak_alias)
<< GA->getAliasedGlobal()->getName() << GA->getName();
Aliasee = llvm::ConstantExpr::getPointerBitCastOrAddrSpaceCast(
GA->getAliasee(), Alias->getType());
Alias->setAliasee(Aliasee);
}
}
}
if (!Error)
return;