#include "llvm/GlobalAlias.h"
#include "llvm/Operator.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ConstantFolding.h"
Visited.insert(V);
do {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
- if (!accumulateGEPOffset(TD, GEP, Offset))
+ if (!GEP->isInBounds() || !accumulateGEPOffset(TD, GEP, Offset))
break;
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast) {
return 0;
}
+static Constant *computePointerICmp(const TargetData &TD,
+ CmpInst::Predicate Pred,
+ Value *LHS, Value *RHS) {
+ // We can only fold certain predicates on pointer comparisons.
+ switch (Pred) {
+ default:
+ return 0;
+
+ // Equality comaprisons are easy to fold.
+ case CmpInst::ICMP_EQ:
+ case CmpInst::ICMP_NE:
+ break;
+
+ // We can only handle unsigned relational comparisons because 'inbounds' on
+ // a GEP only protects against unsigned wrapping.
+ case CmpInst::ICMP_UGT:
+ case CmpInst::ICMP_UGE:
+ case CmpInst::ICMP_ULT:
+ case CmpInst::ICMP_ULE:
+ // However, we have to switch them to their signed variants to handle
+ // negative indices from the base pointer.
+ Pred = ICmpInst::getSignedPredicate(Pred);
+ break;
+ }
+
+ Constant *LHSOffset = stripAndComputeConstantOffsets(TD, LHS);
+ if (!LHSOffset)
+ return 0;
+ Constant *RHSOffset = stripAndComputeConstantOffsets(TD, RHS);
+ if (!RHSOffset)
+ return 0;
+
+ // If LHS and RHS are not related via constant offsets to the same base
+ // value, there is nothing we can do here.
+ if (LHS != RHS)
+ return 0;
+
+ return ConstantExpr::getICmp(Pred, LHSOffset, RHSOffset);
+}
/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
/// fold the result. If not, this returns null.
return getFalse(ITy);
}
- // Simplify comparisons of GEPs.
+ // Simplify comparisons of related pointers using a powerful, recursive
+ // GEP-walk when we have target data available..
+ if (Q.TD && LHS->getType()->isPointerTy() && RHS->getType()->isPointerTy())
+ if (Constant *C = computePointerICmp(*Q.TD, Pred, LHS, RHS))
+ return C;
+
if (GetElementPtrInst *GLHS = dyn_cast<GetElementPtrInst>(LHS)) {
if (GEPOperator *GRHS = dyn_cast<GEPOperator>(RHS)) {
if (GLHS->getPointerOperand() == GRHS->getPointerOperand() &&
return Result == I ? UndefValue::get(I->getType()) : Result;
}
-/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
-/// delete the From instruction. In addition to a basic RAUW, this does a
-/// recursive simplification of the newly formed instructions. This catches
-/// things where one simplification exposes other opportunities. This only
-/// simplifies and deletes scalar operations, it does not change the CFG.
+/// \brief Implementation of recursive simplification through an instructions
+/// uses.
///
-void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
- const TargetData *TD,
- const TargetLibraryInfo *TLI,
- const DominatorTree *DT) {
- assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
-
- // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
- // we can know if it gets deleted out from under us or replaced in a
- // recursive simplification.
- WeakVH FromHandle(From);
- WeakVH ToHandle(To);
-
- while (!From->use_empty()) {
- // Update the instruction to use the new value.
- Use &TheUse = From->use_begin().getUse();
- Instruction *User = cast<Instruction>(TheUse.getUser());
- TheUse = To;
-
- // Check to see if the instruction can be folded due to the operand
- // replacement. For example changing (or X, Y) into (or X, -1) can replace
- // the 'or' with -1.
- Value *SimplifiedVal;
- {
- // Sanity check to make sure 'User' doesn't dangle across
- // SimplifyInstruction.
- AssertingVH<> UserHandle(User);
-
- SimplifiedVal = SimplifyInstruction(User, TD, TLI, DT);
- if (SimplifiedVal == 0) continue;
- }
+/// This is the common implementation of the recursive simplification routines.
+/// If we have a pre-simplified value in 'SimpleV', that is forcibly used to
+/// replace the instruction 'I'. Otherwise, we simply add 'I' to the list of
+/// instructions to process and attempt to simplify it using
+/// InstructionSimplify.
+///
+/// This routine returns 'true' only when *it* simplifies something. The passed
+/// in simplified value does not count toward this.
+static bool replaceAndRecursivelySimplifyImpl(Instruction *I, Value *SimpleV,
+ const TargetData *TD,
+ const TargetLibraryInfo *TLI,
+ const DominatorTree *DT) {
+ bool Simplified = false;
+ SmallSetVector<Instruction *, 8> Worklist;
+
+ // If we have an explicit value to collapse to, do that round of the
+ // simplification loop by hand initially.
+ if (SimpleV) {
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
+ ++UI)
+ if (*UI != I)
+ Worklist.insert(cast<Instruction>(*UI));
+
+ // Replace the instruction with its simplified value.
+ I->replaceAllUsesWith(SimpleV);
+
+ // Gracefully handle edge cases where the instruction is not wired into any
+ // parent block.
+ if (I->getParent())
+ I->eraseFromParent();
+ } else {
+ Worklist.insert(I);
+ }
+
+ // Note that we must test the size on each iteration, the worklist can grow.
+ for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
+ I = Worklist[Idx];
+
+ // See if this instruction simplifies.
+ SimpleV = SimplifyInstruction(I, TD, TLI, DT);
+ if (!SimpleV)
+ continue;
+
+ Simplified = true;
- // Recursively simplify this user to the new value.
- ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, TLI, DT);
- From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
- To = ToHandle;
+ // Stash away all the uses of the old instruction so we can check them for
+ // recursive simplifications after a RAUW. This is cheaper than checking all
+ // uses of To on the recursive step in most cases.
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
+ ++UI)
+ Worklist.insert(cast<Instruction>(*UI));
- assert(ToHandle && "To value deleted by recursive simplification?");
+ // Replace the instruction with its simplified value.
+ I->replaceAllUsesWith(SimpleV);
- // If the recursive simplification ended up revisiting and deleting
- // 'From' then we're done.
- if (From == 0)
- return;
+ // Gracefully handle edge cases where the instruction is not wired into any
+ // parent block.
+ if (I->getParent())
+ I->eraseFromParent();
}
+ return Simplified;
+}
- // If 'From' has value handles referring to it, do a real RAUW to update them.
- From->replaceAllUsesWith(To);
+bool llvm::recursivelySimplifyInstruction(Instruction *I,
+ const TargetData *TD,
+ const TargetLibraryInfo *TLI,
+ const DominatorTree *DT) {
+ return replaceAndRecursivelySimplifyImpl(I, 0, TD, TLI, DT);
+}
- From->eraseFromParent();
+bool llvm::replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV,
+ const TargetData *TD,
+ const TargetLibraryInfo *TLI,
+ const DominatorTree *DT) {
+ assert(I != SimpleV && "replaceAndRecursivelySimplify(X,X) is not valid!");
+ assert(SimpleV && "Must provide a simplified value.");
+ return replaceAndRecursivelySimplifyImpl(I, SimpleV, TD, TLI, DT);
}
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