#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
+#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
Depth+1);
- // The sign of a remainder is equal to the sign of the first
- // operand (zero being positive).
+ // If the sign bit of the first operand is zero, the sign bit of
+ // the result is zero. If the first operand has no one bits below
+ // the second operand's single 1 bit, its sign will be zero.
if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits))
KnownZero2 |= ~LowBits;
- else if (KnownOne2[BitWidth-1])
- KnownOne2 |= ~LowBits;
KnownZero |= KnownZero2 & Mask;
- KnownOne |= KnownOne2 & Mask;
assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
}
ComputeMaskedBits(R, Mask2, KnownZero2, KnownOne2, TD, Depth+1);
Mask2 = APInt::getLowBitsSet(BitWidth,
KnownZero2.countTrailingOnes());
- KnownOne2.clear();
- KnownZero2.clear();
- ComputeMaskedBits(L, Mask2, KnownZero2, KnownOne2, TD, Depth+1);
+
+ // We need to take the minimum number of known bits
+ APInt KnownZero3(KnownZero), KnownOne3(KnownOne);
+ ComputeMaskedBits(L, Mask2, KnownZero3, KnownOne3, TD, Depth+1);
+
KnownZero = Mask &
APInt::getLowBitsSet(BitWidth,
- KnownZero2.countTrailingOnes());
+ std::min(KnownZero2.countTrailingOnes(),
+ KnownZero3.countTrailingOnes()));
break;
}
}
Value *BuildSubAggregate(Value *From, Value* To, const Type *IndexedType,
SmallVector<unsigned, 10> &Idxs,
unsigned IdxSkip,
- Instruction &InsertBefore) {
+ Instruction *InsertBefore) {
const llvm::StructType *STy = llvm::dyn_cast<llvm::StructType>(IndexedType);
if (STy) {
+ // Save the original To argument so we can modify it
+ Value *OrigTo = To;
// General case, the type indexed by Idxs is a struct
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
// Process each struct element recursively
Idxs.push_back(i);
- To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip, InsertBefore);
+ Value *PrevTo = To;
+ To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
+ InsertBefore);
Idxs.pop_back();
+ if (!To) {
+ // Couldn't find any inserted value for this index? Cleanup
+ while (PrevTo != OrigTo) {
+ InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
+ PrevTo = Del->getAggregateOperand();
+ Del->eraseFromParent();
+ }
+ // Stop processing elements
+ break;
+ }
}
- return To;
- } else {
- // Base case, the type indexed by SourceIdxs is not a struct
- // Load the value from the nested struct into the sub struct (and skip
- // IdxSkip indices when indexing the sub struct).
- Instruction *V = llvm::ExtractValueInst::Create(From, Idxs.begin(), Idxs.end(), "tmp", &InsertBefore);
- Instruction *Ins = llvm::InsertValueInst::Create(To, V, Idxs.begin() + IdxSkip, Idxs.end(), "tmp", &InsertBefore);
- return Ins;
+ // If we succesfully found a value for each of our subaggregates
+ if (To)
+ return To;
}
+ // Base case, the type indexed by SourceIdxs is not a struct, or not all of
+ // the struct's elements had a value that was inserted directly. In the latter
+ // case, perhaps we can't determine each of the subelements individually, but
+ // we might be able to find the complete struct somewhere.
+
+ // Find the value that is at that particular spot
+ Value *V = FindInsertedValue(From, Idxs.begin(), Idxs.end());
+
+ if (!V)
+ return NULL;
+
+ // Insert the value in the new (sub) aggregrate
+ return llvm::InsertValueInst::Create(To, V, Idxs.begin() + IdxSkip,
+ Idxs.end(), "tmp", InsertBefore);
}
// This helper takes a nested struct and extracts a part of it (which is again a
// and the indices "1, 1" this returns
// { c, d }.
//
-// It does this by inserting an extractvalue and insertvalue for each element in
-// the resulting struct, as opposed to just inserting a single struct. This
-// allows for later folding of these individual extractvalue instructions with
-// insertvalue instructions that fill the nested struct.
+// It does this by inserting an insertvalue for each element in the resulting
+// struct, as opposed to just inserting a single struct. This will only work if
+// each of the elements of the substruct are known (ie, inserted into From by an
+// insertvalue instruction somewhere).
//
-// Any inserted instructions are inserted before InsertBefore
-Value *BuildSubAggregate(Value *From, const unsigned *idx_begin, const unsigned *idx_end, Instruction &InsertBefore) {
- const Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(), idx_begin, idx_end);
+// All inserted insertvalue instructions are inserted before InsertBefore
+Value *BuildSubAggregate(Value *From, const unsigned *idx_begin,
+ const unsigned *idx_end, Instruction *InsertBefore) {
+ assert(InsertBefore && "Must have someplace to insert!");
+ const Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
+ idx_begin,
+ idx_end);
Value *To = UndefValue::get(IndexedType);
SmallVector<unsigned, 10> Idxs(idx_begin, idx_end);
unsigned IdxSkip = Idxs.size();
return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
}
-/// FindInsertedValue - Given an aggregrate and an sequence of indices, see if the
-/// scalar value indexed is already around as a register, for example if it were
-/// inserted directly into the aggregrate.
+/// FindInsertedValue - Given an aggregrate and an sequence of indices, see if
+/// the scalar value indexed is already around as a register, for example if it
+/// were inserted directly into the aggregrate.
+///
+/// If InsertBefore is not null, this function will duplicate (modified)
+/// insertvalues when a part of a nested struct is extracted.
Value *llvm::FindInsertedValue(Value *V, const unsigned *idx_begin,
- const unsigned *idx_end, Instruction &InsertBefore) {
+ const unsigned *idx_end, Instruction *InsertBefore) {
// Nothing to index? Just return V then (this is useful at the end of our
// recursion)
if (idx_begin == idx_end)
else if (Constant *C = dyn_cast<Constant>(V)) {
if (isa<ConstantArray>(C) || isa<ConstantStruct>(C))
// Recursively process this constant
- return FindInsertedValue(C->getOperand(*idx_begin), ++idx_begin, idx_end, InsertBefore);
+ return FindInsertedValue(C->getOperand(*idx_begin), idx_begin + 1, idx_end,
+ InsertBefore);
} else if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
// Loop the indices for the insertvalue instruction in parallel with the
// requested indices
const unsigned *req_idx = idx_begin;
- for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); i != e; ++i, ++req_idx) {
- if (req_idx == idx_end)
- // The requested index is a part of a nested aggregate. Handle this
- // specially.
- return BuildSubAggregate(V, idx_begin, req_idx, InsertBefore);
+ for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
+ i != e; ++i, ++req_idx) {
+ if (req_idx == idx_end) {
+ if (InsertBefore)
+ // The requested index identifies a part of a nested aggregate. Handle
+ // this specially. For example,
+ // %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
+ // %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
+ // %C = extractvalue {i32, { i32, i32 } } %B, 1
+ // This can be changed into
+ // %A = insertvalue {i32, i32 } undef, i32 10, 0
+ // %C = insertvalue {i32, i32 } %A, i32 11, 1
+ // which allows the unused 0,0 element from the nested struct to be
+ // removed.
+ return BuildSubAggregate(V, idx_begin, req_idx, InsertBefore);
+ else
+ // We can't handle this without inserting insertvalues
+ return 0;
+ }
// This insert value inserts something else than what we are looking for.
// See if the (aggregrate) value inserted into has the value we are
// looking for, then.
if (*req_idx != *i)
- return FindInsertedValue(I->getAggregateOperand(), idx_begin, idx_end, InsertBefore);
+ return FindInsertedValue(I->getAggregateOperand(), idx_begin, idx_end,
+ InsertBefore);
}
// If we end up here, the indices of the insertvalue match with those
// requested (though possibly only partially). Now we recursively look at
// the inserted value, passing any remaining indices.
- return FindInsertedValue(I->getInsertedValueOperand(), req_idx, idx_end, InsertBefore);
+ return FindInsertedValue(I->getInsertedValueOperand(), req_idx, idx_end,
+ InsertBefore);
} else if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
// If we're extracting a value from an aggregrate that was extracted from
// something else, we can extract from that something else directly instead.
// Calculate the number of indices required
unsigned size = I->getNumIndices() + (idx_end - idx_begin);
// Allocate some space to put the new indices in
- unsigned *new_begin = new unsigned[size];
- // Auto cleanup this array
- std::auto_ptr<unsigned> newptr(new_begin);
- // Start inserting at the beginning
- unsigned *new_end = new_begin;
+ SmallVector<unsigned, 5> Idxs;
+ Idxs.reserve(size);
// Add indices from the extract value instruction
- for (const unsigned *i = I->idx_begin(), *e = I->idx_end(); i != e; ++i, ++new_end)
- *new_end = *i;
+ for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
+ i != e; ++i)
+ Idxs.push_back(*i);
// Add requested indices
- for (const unsigned *i = idx_begin, *e = idx_end; i != e; ++i, ++new_end)
- *new_end = *i;
+ for (const unsigned *i = idx_begin, *e = idx_end; i != e; ++i)
+ Idxs.push_back(*i);
- assert((unsigned)(new_end - new_begin) == size && "Number of indices added not correct?");
+ assert(Idxs.size() == size
+ && "Number of indices added not correct?");
- return FindInsertedValue(I->getAggregateOperand(), new_begin, new_end, InsertBefore);
+ return FindInsertedValue(I->getAggregateOperand(), Idxs.begin(), Idxs.end(),
+ InsertBefore);
}
// Otherwise, we don't know (such as, extracting from a function return value
// or load instruction)
return 0;
}
+
+/// GetConstantStringInfo - This function computes the length of a
+/// null-terminated C string pointed to by V. If successful, it returns true
+/// and returns the string in Str. If unsuccessful, it returns false.
+bool llvm::GetConstantStringInfo(Value *V, std::string &Str, uint64_t Offset,
+ bool StopAtNul) {
+ // If V is NULL then return false;
+ if (V == NULL) return false;
+
+ // Look through bitcast instructions.
+ if (BitCastInst *BCI = dyn_cast<BitCastInst>(V))
+ return GetConstantStringInfo(BCI->getOperand(0), Str, Offset, StopAtNul);
+
+ // If the value is not a GEP instruction nor a constant expression with a
+ // GEP instruction, then return false because ConstantArray can't occur
+ // any other way
+ User *GEP = 0;
+ if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(V)) {
+ GEP = GEPI;
+ } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ if (CE->getOpcode() == Instruction::BitCast)
+ return GetConstantStringInfo(CE->getOperand(0), Str, Offset, StopAtNul);
+ if (CE->getOpcode() != Instruction::GetElementPtr)
+ return false;
+ GEP = CE;
+ }
+
+ if (GEP) {
+ // Make sure the GEP has exactly three arguments.
+ if (GEP->getNumOperands() != 3)
+ return false;
+
+ // Make sure the index-ee is a pointer to array of i8.
+ const PointerType *PT = cast<PointerType>(GEP->getOperand(0)->getType());
+ const ArrayType *AT = dyn_cast<ArrayType>(PT->getElementType());
+ if (AT == 0 || AT->getElementType() != Type::Int8Ty)
+ return false;
+
+ // Check to make sure that the first operand of the GEP is an integer and
+ // has value 0 so that we are sure we're indexing into the initializer.
+ ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
+ if (FirstIdx == 0 || !FirstIdx->isZero())
+ return false;
+
+ // If the second index isn't a ConstantInt, then this is a variable index
+ // into the array. If this occurs, we can't say anything meaningful about
+ // the string.
+ uint64_t StartIdx = 0;
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
+ StartIdx = CI->getZExtValue();
+ else
+ return false;
+ return GetConstantStringInfo(GEP->getOperand(0), Str, StartIdx+Offset,
+ StopAtNul);
+ }
+
+ // The GEP instruction, constant or instruction, must reference a global
+ // variable that is a constant and is initialized. The referenced constant
+ // initializer is the array that we'll use for optimization.
+ GlobalVariable* GV = dyn_cast<GlobalVariable>(V);
+ if (!GV || !GV->isConstant() || !GV->hasInitializer())
+ return false;
+ Constant *GlobalInit = GV->getInitializer();
+
+ // Handle the ConstantAggregateZero case
+ if (isa<ConstantAggregateZero>(GlobalInit)) {
+ // This is a degenerate case. The initializer is constant zero so the
+ // length of the string must be zero.
+ Str.clear();
+ return true;
+ }
+
+ // Must be a Constant Array
+ ConstantArray *Array = dyn_cast<ConstantArray>(GlobalInit);
+ if (Array == 0 || Array->getType()->getElementType() != Type::Int8Ty)
+ return false;
+
+ // Get the number of elements in the array
+ uint64_t NumElts = Array->getType()->getNumElements();
+
+ if (Offset > NumElts)
+ return false;
+
+ // Traverse the constant array from 'Offset' which is the place the GEP refers
+ // to in the array.
+ Str.reserve(NumElts-Offset);
+ for (unsigned i = Offset; i != NumElts; ++i) {
+ Constant *Elt = Array->getOperand(i);
+ ConstantInt *CI = dyn_cast<ConstantInt>(Elt);
+ if (!CI) // This array isn't suitable, non-int initializer.
+ return false;
+ if (StopAtNul && CI->isZero())
+ return true; // we found end of string, success!
+ Str += (char)CI->getZExtValue();
+ }
+
+ // The array isn't null terminated, but maybe this is a memcpy, not a strcpy.
+ return true;
+}