maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[DSE] Assert analyzable write in isRemovable() (NFC) 

As requested on D116210. The function is not necessarily well-defined
without this precondition.
This commit is contained in:
Nikita Popov 2021-12-24 09:37:25 +01:00
parent 2b8a703858
commit 034e66e76c
1 changed files with 25 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -175,30 +175,6 @@ static cl::opt<bool>
using OverlapIntervalsTy = std::map<int64_t, int64_t>; using OverlapIntervalsTy = std::map<int64_t, int64_t>;
using InstOverlapIntervalsTy = DenseMap<Instruction *, OverlapIntervalsTy>; using InstOverlapIntervalsTy = DenseMap<Instruction *, OverlapIntervalsTy>;
/// If the value of this instruction and the memory it writes to is unused, may
/// we delete this instruction?
static bool isRemovable(Instruction *I) {
// Don't remove volatile/atomic stores.
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isUnordered();
// Note: only get here for calls with analyzable writes.
if (auto *CB = dyn_cast<CallBase>(I)) {
// Don't remove volatile memory intrinsics.
if (auto *MI = dyn_cast<MemIntrinsic>(CB))
return !MI->isVolatile();
// Never remove dead lifetime intrinsics, e.g. because they are followed by
// a free.
if (CB->isLifetimeStartOrEnd())
return false;
return CB->use_empty() && CB->willReturn() && CB->doesNotThrow();
}
return false;
}
/// Returns true if the end of this instruction can be safely shortened in /// Returns true if the end of this instruction can be safely shortened in
/// length. /// length.
static bool isShortenableAtTheEnd(Instruction *I) { static bool isShortenableAtTheEnd(Instruction *I) {
@ -1024,6 +1000,31 @@ struct DSEState {
return MemoryLocation::getOrNone(I); return MemoryLocation::getOrNone(I);
} }
/// Assuming this instruction has a dead analyzable write, can we delete
/// this instruction?
bool isRemovable(Instruction *I) {
assert(getLocForWriteEx(I) && "Must have analyzable write");
// Don't remove volatile/atomic stores.
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isUnordered();
if (auto *CB = dyn_cast<CallBase>(I)) {
// Don't remove volatile memory intrinsics.
if (auto *MI = dyn_cast<MemIntrinsic>(CB))
return !MI->isVolatile();
// Never remove dead lifetime intrinsics, e.g. because they are followed
// by a free.
if (CB->isLifetimeStartOrEnd())
return false;
return CB->use_empty() && CB->willReturn() && CB->doesNotThrow();
}
return false;
}
/// Returns true if \p UseInst completely overwrites \p DefLoc /// Returns true if \p UseInst completely overwrites \p DefLoc
/// (stored by \p DefInst). /// (stored by \p DefInst).
bool isCompleteOverwrite(const MemoryLocation &DefLoc, Instruction *DefInst, bool isCompleteOverwrite(const MemoryLocation &DefLoc, Instruction *DefInst,