#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;
}
}
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,
+ 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
// 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;
+}
projects / oota-llvm.git / blobdiff