Fix PR9815: I was trying to get out of "generating code and then
failing to form a memset, then having to delete it" but my approximation
isn't safe for self recurrent loops. Instead of doign a hack, just
do it the right way.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131858 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 08d96ed..dbf6eec 100644
--- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -128,11 +128,11 @@
Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); }
-/// DeleteDeadInstruction - Delete this instruction. Before we do, go through
+/// deleteDeadInstruction - Delete this instruction. Before we do, go through
/// and zero out all the operands of this instruction. If any of them become
/// dead, delete them and the computation tree that feeds them.
///
-static void DeleteDeadInstruction(Instruction *I, ScalarEvolution &SE) {
+static void deleteDeadInstruction(Instruction *I, ScalarEvolution &SE) {
SmallVector<Instruction*, 32> NowDeadInsts;
NowDeadInsts.push_back(I);
@@ -162,6 +162,14 @@
} while (!NowDeadInsts.empty());
}
+/// deleteIfDeadInstruction - If the specified value is a dead instruction,
+/// delete it and any recursively used instructions.
+static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE) {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ if (isInstructionTriviallyDead(I))
+ deleteDeadInstruction(I, SE);
+}
+
bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
CurLoop = L;
@@ -454,31 +462,35 @@
return false;
}
-
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE);
+
// Okay, we have a strided store "p[i]" of a splattable value. We can turn
// this into a memset in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the aliased location. Check for an alias.
- if (mayLoopAccessLocation(DestPtr, AliasAnalysis::ModRef,
- CurLoop, BECount,
- StoreSize, getAnalysis<AliasAnalysis>(), TheStore))
- return false;
-
- // Okay, everything looks good, insert the memset.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
+ // or write to the aliased location. Check for any overlap by generating the
+ // base pointer and checking the region.
unsigned AddrSpace = cast<PointerType>(DestPtr->getType())->getAddressSpace();
Value *BasePtr =
Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace),
Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(BasePtr, AliasAnalysis::ModRef,
+ CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), TheStore)){
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(BasePtr, *SE);
+ return false;
+ }
+
+ // Okay, everything looks good, insert the memset.
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
const Type *IntPtr = TD->getIntPtrType(DestPtr->getContext());
@@ -521,7 +533,7 @@
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(TheStore, *SE);
+ deleteDeadInstruction(TheStore, *SE);
++NumMemSet;
return true;
}
@@ -539,41 +551,51 @@
LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE);
+
// Okay, we have a strided store "p[i]" of a loaded value. We can turn
// this into a memcpy in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the stored location (including the load feeding the stores).
- // Check for an alias.
- if (mayLoopAccessLocation(SI->getPointerOperand(), AliasAnalysis::ModRef,
- CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
- return false;
-
- // For a memcpy, we have to make sure that the input array is not being
- // mutated by the loop.
- if (mayLoopAccessLocation(LI->getPointerOperand(), AliasAnalysis::Mod,
- CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
- return false;
-
- // Okay, everything looks good, insert the memcpy.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
- Value *LoadBasePtr =
- Expander.expandCodeFor(LoadEv->getStart(),
- Builder.getInt8PtrTy(LI->getPointerAddressSpace()),
- Preheader->getTerminator());
+ // or write the memory region we're storing to. This includes the load that
+ // feeds the stores. Check for an alias by generating the base address and
+ // checking everything.
Value *StoreBasePtr =
Expander.expandCodeFor(StoreEv->getStart(),
Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(StoreBasePtr, AliasAnalysis::ModRef,
+ CurLoop, BECount, StoreSize,
+ getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(StoreBasePtr, *SE);
+ return false;
+ }
+
+ // For a memcpy, we have to make sure that the input array is not being
+ // mutated by the loop.
+ Value *LoadBasePtr =
+ Expander.expandCodeFor(LoadEv->getStart(),
+ Builder.getInt8PtrTy(LI->getPointerAddressSpace()),
+ Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(LoadBasePtr, AliasAnalysis::Mod, CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(LoadBasePtr, *SE);
+ deleteIfDeadInstruction(StoreBasePtr, *SE);
+ return false;
+ }
+
+ // Okay, everything is safe, we can transform this!
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
@@ -601,7 +623,7 @@
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(SI, *SE);
+ deleteDeadInstruction(SI, *SE);
++NumMemCpy;
return true;
}