diff options
Diffstat (limited to 'llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp index 1ea0b15e4c9..02df1031e60 100644 --- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp +++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp @@ -217,9 +217,28 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) { continue; } - // If not a definite must-alias dependency, ignore it. - if (!InstDep.isDef()) - continue; + if (!InstDep.isDef()) { + // If this is a may-aliased store that is clobbering the store value, we + // can keep searching past it for another must-aliased pointer that stores + // to the same location. For example, in: + // store -> P + // store -> Q + // store -> P + // we can remove the first store to P even though we don't know if P and Q + // alias. + if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { + AliasAnalysis::Location Loc = + getAnalysis<AliasAnalysis>().getLocation(SI); + while (InstDep.isClobber() && isa<StoreInst>(InstDep.getInst()) && + InstDep.getInst() != &BB.front()) + InstDep = MD.getPointerDependencyFrom(Loc, false, InstDep.getInst(), + &BB); + } + + // If not a definite must-alias dependency, ignore it. + if (!InstDep.isDef()) + continue; + } // If this is a store-store dependence, then the previous store is dead so // long as this store is at least as big as it. |
