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Hoist out some work done inside a loop doing a linear scan over all

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instructions in a block. GetUnderlyingObject is more expensive than it looks as
it can, for instance, call SimplifyInstruction.

This might have some behavioural changes in odd corner cases, but only because
of some strange artefacts of the original implementation. If you were relying
on those, we can fix that by replacing this with a smarter algorithm. Change
passes the existing tests.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166754 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2012-10-26 04:43:47 +00:00
parent dc330f75b7
commit 4734fe19f6
1 changed files with 17 additions and 12 deletions
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29
lib/Analysis/LazyValueInfo.cpp
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@ -13,6 +13,7 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "lazy-value-info"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Constants.h"
@ -294,7 +295,7 @@ raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
//===----------------------------------------------------------------------===//
namespace {
/// LVIValueHandle - A callback value handle update the cache when
/// LVIValueHandle - A callback value handle updates the cache when
/// values are erased.
class LazyValueInfoCache;
struct LVIValueHandle : public CallbackVH {
@ -557,13 +558,11 @@ bool LazyValueInfoCache::solveBlockValue(Value *Val, BasicBlock *BB) {
static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
if (LoadInst *L = dyn_cast<LoadInst>(I)) {
return L->getPointerAddressSpace() == 0 &&
GetUnderlyingObject(L->getPointerOperand()) ==
GetUnderlyingObject(Ptr);
GetUnderlyingObject(L->getPointerOperand()) == Ptr;
}
if (StoreInst *S = dyn_cast<StoreInst>(I)) {
return S->getPointerAddressSpace() == 0 &&
GetUnderlyingObject(S->getPointerOperand()) ==
GetUnderlyingObject(Ptr);
GetUnderlyingObject(S->getPointerOperand()) == Ptr;
}
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
if (MI->isVolatile()) return false;
@ -573,11 +572,11 @@ static bool InstructionDereferencesPointer(Instruction *I, Value *Ptr) {
if (!Len || Len->isZero()) return false;
if (MI->getDestAddressSpace() == 0)
if (MI->getRawDest() == Ptr || MI->getDest() == Ptr)
if (GetUnderlyingObject(MI->getRawDest()) == Ptr)
return true;
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
if (MTI->getSourceAddressSpace() == 0)
if (MTI->getRawSource() == Ptr || MTI->getSource() == Ptr)
if (GetUnderlyingObject(MTI->getRawSource()) == Ptr)
return true;
}
return false;
@ -591,13 +590,19 @@ bool LazyValueInfoCache::solveBlockValueNonLocal(LVILatticeVal &BBLV,
// then we know that the pointer can't be NULL.
bool NotNull = false;
if (Val->getType()->isPointerTy()) {
if (isa<AllocaInst>(Val)) {
if (isKnownNonNull(Val)) {
NotNull = true;
} else {
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();BI != BE;++BI){
if (InstructionDereferencesPointer(BI, Val)) {
NotNull = true;
break;
Value *UnderlyingVal = GetUnderlyingObject(Val);
// If 'GetUnderlyingObject' didn't converge, skip it. It won't converge
// inside InstructionDereferencesPointer either.
if (UnderlyingVal == GetUnderlyingObject(UnderlyingVal, NULL, 1)) {
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE; ++BI) {
if (InstructionDereferencesPointer(BI, UnderlyingVal)) {
NotNull = true;
break;
}
}
}
}