Treat lifetime begin/end markers as allocations/frees respectively for the
purposes for GVN/DSE.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85383 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index be5f9c1..0ec0e74 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -185,10 +185,9 @@
if (invariantTag == Inst) {
invariantTag = 0;
continue;
-
- // If we pass an invariant-end marker, then we've just entered an invariant
- // region and can start ignoring dependencies.
} else if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst)) {
+ // If we pass an invariant-end marker, then we've just entered an
+ // invariant region and can start ignoring dependencies.
if (II->getIntrinsicID() == Intrinsic::invariant_end) {
uint64_t invariantSize = ~0ULL;
if (ConstantInt* CI = dyn_cast<ConstantInt>(II->getOperand(2)))
@@ -200,6 +199,19 @@
invariantTag = II->getOperand(1);
continue;
}
+
+ // If we reach a lifetime begin or end marker, then the query ends here
+ // because the value is undefined.
+ } else if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end) {
+ uint64_t invariantSize = ~0ULL;
+ if (ConstantInt* CI = dyn_cast<ConstantInt>(II->getOperand(1)))
+ invariantSize = CI->getZExtValue();
+
+ AliasAnalysis::AliasResult R =
+ AA->alias(II->getOperand(2), invariantSize, MemPtr, MemSize);
+ if (R == AliasAnalysis::MustAlias)
+ return MemDepResult::getDef(II);
}
}
diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index e3f4337..60b12fd 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -154,6 +154,26 @@
continue;
}
}
+
+ // If this is a lifetime end marker, we can throw away the store.
+ if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(InstDep.getInst())) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_end) {
+ // Delete the store and now-dead instructions that feed it.
+ // DeleteDeadInstruction can delete the current instruction. Save BBI
+ // in case we need it.
+ WeakVH NextInst(BBI);
+
+ DeleteDeadInstruction(SI);
+
+ if (NextInst == 0) // Next instruction deleted.
+ BBI = BB.begin();
+ else if (BBI != BB.begin()) // Revisit this instruction if possible.
+ --BBI;
+ NumFastStores++;
+ MadeChange = true;
+ continue;
+ }
+ }
}
// If this block ends in a return, unwind, or unreachable, all allocas are
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 32d027a..dd8859b 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1248,6 +1248,15 @@
UndefValue::get(LI->getType())));
continue;
}
+
+ // Loading immediately after lifetime begin or end -> undef.
+ if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(DepInst)) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end) {
+ ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
+ UndefValue::get(LI->getType())));
+ }
+ }
if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
// Reject loads and stores that are to the same address but are of
@@ -1591,6 +1600,18 @@
NumGVNLoad++;
return true;
}
+
+ // If this load occurs either right after a lifetime begin or a lifetime end,
+ // then the loaded value is undefined.
+ if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(DepInst)) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end) {
+ L->replaceAllUsesWith(UndefValue::get(L->getType()));
+ toErase.push_back(L);
+ NumGVNLoad++;
+ return true;
+ }
+ }
return false;
}