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BitcodeReader: Only create one basic block for each blockaddress

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Block address forward-references are implemented by creating a
`BasicBlock` ahead of time that gets inserted in the `Function` when
it's eventually encountered.

However, if the same blockaddress was used in two separate functions
that were parsed *before* the referenced function (and the blockaddress
was never used at global scope), two separate basic blocks would get
created, one of which would be forgotten creating invalid IR.

This commit changes the forward-reference logic to create only one basic
block (and always return the same blockaddress).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215805 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2014-08-16 01:54:37 +00:00
parent 1e97329f27
commit 1d8c9d95bf
3 changed files with 32 additions and 20 deletions
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32
lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -1635,11 +1635,14 @@ std::error_code BitcodeReader::ParseConstants() {
} else {
// Otherwise insert a placeholder and remember it so it can be inserted
// when the function is parsed.
BB = BasicBlock::Create(Context);
auto &FwdBBs = BasicBlockFwdRefs[Fn];
if (FwdBBs.empty())
BasicBlockFwdRefQueue.push_back(Fn);
FwdBBs.emplace_back(BBID, BB);
if (FwdBBs.size() < BBID + 1)
FwdBBs.resize(BBID + 1);
if (!FwdBBs[BBID])
FwdBBs[BBID] = BasicBlock::Create(Context);
BB = FwdBBs[BBID];
}
V = BlockAddress::get(Fn, BB);
break;
@ -2392,24 +2395,19 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
FunctionBBs[i] = BasicBlock::Create(Context, "", F);
} else {
auto &BBRefs = BBFRI->second;
std::sort(BBRefs.begin(), BBRefs.end(),
[](const std::pair<unsigned, BasicBlock *> &LHS,
const std::pair<unsigned, BasicBlock *> &RHS) {
return LHS.first < RHS.first;
});
unsigned R = 0, RE = BBRefs.size();
for (unsigned I = 0, E = FunctionBBs.size(); I != E; ++I)
if (R != RE && BBRefs[R].first == I) {
assert(I != 0 && "Invalid reference to entry block");
BasicBlock *BB = BBRefs[R++].second;
BB->insertInto(F);
FunctionBBs[I] = BB;
// Check for invalid basic block references.
if (BBRefs.size() > FunctionBBs.size())
return Error(BitcodeError::InvalidID);
assert(!BBRefs.empty() && "Unexpected empty array");
assert(!BBRefs.front() && "Invalid reference to entry block");
for (unsigned I = 0, E = FunctionBBs.size(), RE = BBRefs.size(); I != E;
++I)
if (I < RE && BBRefs[I]) {
BBRefs[I]->insertInto(F);
FunctionBBs[I] = BBRefs[I];
} else {
FunctionBBs[I] = BasicBlock::Create(Context, "", F);
}
// Check for invalid basic block references.
if (R != RE)
return Error(BitcodeError::InvalidID);
// Erase from the table.
BasicBlockFwdRefs.erase(BBFRI);

6
lib/Bitcode/Reader/BitcodeReader.h
View File

@ -181,9 +181,9 @@ class BitcodeReader : public GVMaterializer {
DenseMap<Function*, uint64_t> DeferredFunctionInfo;
/// These are basic blocks forward-referenced by block addresses. They are
/// inserted lazily into functions when they're loaded.
typedef std::pair<unsigned, BasicBlock *> BasicBlockRefTy;
DenseMap<Function *, std::vector<BasicBlockRefTy>> BasicBlockFwdRefs;
/// inserted lazily into functions when they're loaded. The basic block ID is
/// its index into the vector.
DenseMap<Function *, std::vector<BasicBlock *>> BasicBlockFwdRefs;
std::deque<Function *> BasicBlockFwdRefQueue;
/// UseRelativeIDs - Indicates that we are using a new encoding for

14
test/Bitcode/blockaddress.ll
View File

@ -44,3 +44,17 @@ here:
end:
ret void
}
; Check a blockaddress taken in two separate functions before the referenced
; function.
define i8* @take1() {
ret i8* blockaddress(@taken, %bb)
}
define i8* @take2() {
ret i8* blockaddress(@taken, %bb)
}
define void @taken() {
unreachable
bb:
unreachable
}