[llvm-commits] [llvm] r67979 - in /llvm/trunk/include/llvm: ADT/PointerIntPair.h Instruction.h Support/PointerLikeTypeTraits.h Use.h
Chris Lattner
sabre at nondot.org
Sat Mar 28 21:32:38 PDT 2009
Author: lattner
Date: Sat Mar 28 23:32:37 2009
New Revision: 67979
URL: http://llvm.org/viewvc/llvm-project?rev=67979&view=rev
Log:
Replace the PointerLikeTypeTraits::getNumLowBitsAvailable
function with a new NumLowBitsAvailable enum, which makes the
value available as an integer constant expression.
Add PointerLikeTypeTraits specializations for Instruction* and
Use** since they are only guaranteed 4-byte aligned.
Enhance PointerIntPair to know about (and enforce) the alignment
specified by PointerLikeTypeTraits. This should allow things
like PointerIntPair<PointerIntPair<void*, 1,bool>, 1, bool>
because the inner one knows that 2 low bits are free.
Modified:
llvm/trunk/include/llvm/ADT/PointerIntPair.h
llvm/trunk/include/llvm/Instruction.h
llvm/trunk/include/llvm/Support/PointerLikeTypeTraits.h
llvm/trunk/include/llvm/Use.h
Modified: llvm/trunk/include/llvm/ADT/PointerIntPair.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/PointerIntPair.h?rev=67979&r1=67978&r2=67979&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/PointerIntPair.h (original)
+++ llvm/trunk/include/llvm/ADT/PointerIntPair.h Sat Mar 28 23:32:37 2009
@@ -15,50 +15,77 @@
#define LLVM_ADT_POINTERINTPAIR_H
#include "llvm/Support/DataTypes.h"
+#include "llvm/Support/PointerLikeTypeTraits.h"
#include <cassert>
namespace llvm {
template<typename T>
struct DenseMapInfo;
-template<typename>
-class PointerLikeTypeTraits;
/// PointerIntPair - This class implements a pair of a pointer and small
/// integer. It is designed to represent this in the space required by one
/// pointer by bitmangling the integer into the low part of the pointer. This
/// can only be done for small integers: typically up to 3 bits, but it depends
-/// on the alignment returned by the allocator in use.
+/// on the number of bits available according to PointerLikeTypeTraits for the
+/// type.
+///
+/// Note that PointerIntPair always puts the Int part in the highest bits
+/// possible. For example, PointerIntPair<void*, 1,bool> will put the bit for
+/// the bool into bit #2, not bit #0, which allows the low two bits to be used
+/// for something else. For example, this allows:
+/// PointerIntPair<PointerIntPair<void*, 1,bool>, 1, bool>
+/// ... and the two bools will land in different bits.
///
template <typename PointerTy, unsigned IntBits, typename IntType=unsigned>
class PointerIntPair {
intptr_t Value;
+ typedef PointerLikeTypeTraits<PointerTy> PtrTraits;
+ enum {
+ /// PointerBitMask - The bits that come from the pointer.
+ PointerBitMask = ~(((intptr_t)1 << PtrTraits::NumLowBitsAvailable)-1),
+ /// IntShift - The number of low bits that we reserve for other uses, and
+ /// keep zero.
+ IntShift = PtrTraits::NumLowBitsAvailable-IntBits,
+
+ /// IntMask - This is the unshifted mask for valid bits of the int type.
+ IntMask = ((intptr_t)1 << IntBits)-1,
+
+ // ShiftedIntMask - This is the bits for the integer shifted in place.
+ ShiftedIntMask = IntMask << IntShift
+ };
public:
PointerIntPair() : Value(0) {}
PointerIntPair(PointerTy Ptr, IntType Int) : Value(0) {
+ assert(IntBits <= PtrTraits::NumLowBitsAvailable &&
+ "PointerIntPair formed with integer size too large for pointer");
setPointer(Ptr);
setInt(Int);
}
PointerTy getPointer() const {
- return reinterpret_cast<PointerTy>(Value & ~((1 << IntBits)-1));
+ return reinterpret_cast<PointerTy>(Value & PointerBitMask);
}
IntType getInt() const {
- return (IntType)(Value & ((1 << IntBits)-1));
+ return (IntType)((Value >> IntShift) & IntMask);
}
void setPointer(PointerTy Ptr) {
intptr_t PtrVal = reinterpret_cast<intptr_t>(Ptr);
- assert((PtrVal & ((1 << IntBits)-1)) == 0 &&
+ assert((PtrVal & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
"Pointer is not sufficiently aligned");
- Value = PtrVal | (intptr_t)getInt();
+ // Preserve all low bits, just update the pointer.
+ Value = PtrVal | (Value & ~PointerBitMask);
}
void setInt(IntType Int) {
intptr_t IntVal = Int;
assert(IntVal < (1 << IntBits) && "Integer too large for field");
- Value = reinterpret_cast<intptr_t>(getPointer()) | IntVal;
+
+ // Preserve all bits other than the ones we are updating.
+ Value &= ~ShiftedIntMask; // Remove integer field.
+ Value |= IntVal << IntShift; // Set new integer.
}
void *getOpaqueValue() const { return reinterpret_cast<void*>(Value); }
@@ -107,7 +134,10 @@
getFromVoidPointer(void *P) {
return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
}
- static inline unsigned getNumLowBitsAvailable() { return 0; }
+ enum {
+ NumLowBitsAvailable =
+ PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable - IntBits
+ };
};
} // end namespace llvm
Modified: llvm/trunk/include/llvm/Instruction.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Instruction.h?rev=67979&r1=67978&r2=67979&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Instruction.h (original)
+++ llvm/trunk/include/llvm/Instruction.h Sat Mar 28 23:32:37 2009
@@ -227,6 +227,18 @@
};
};
+// Instruction* is only 4-byte aligned.
+template<>
+class PointerLikeTypeTraits<Instruction*> {
+ typedef Instruction* PT;
+public:
+ static inline void *getAsVoidPointer(PT P) { return P; }
+ static inline PT getFromVoidPointer(void *P) {
+ return static_cast<PT>(P);
+ }
+ enum { NumLowBitsAvailable = 2 };
+};
+
} // End llvm namespace
#endif
Modified: llvm/trunk/include/llvm/Support/PointerLikeTypeTraits.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/PointerLikeTypeTraits.h?rev=67979&r1=67978&r2=67979&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/PointerLikeTypeTraits.h (original)
+++ llvm/trunk/include/llvm/Support/PointerLikeTypeTraits.h Sat Mar 28 23:32:37 2009
@@ -42,7 +42,7 @@
///
/// All clients should use assertions to do a run-time check to ensure that
/// this is actually true.
- static inline unsigned getNumLowBitsAvailable() { return 3; }
+ enum { NumLowBitsAvailable = 3 };
};
// Provide PointerLikeTypeTraits for const pointers.
@@ -53,7 +53,7 @@
static inline const T *getFromVoidPointer(const void *P) {
return static_cast<const T*>(P);
}
- static inline unsigned getNumLowBitsAvailable() { return 3; }
+ enum { NumLowBitsAvailable = 3 };
};
} // end namespace llvm
Modified: llvm/trunk/include/llvm/Use.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Use.h?rev=67979&r1=67978&r2=67979&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Use.h (original)
+++ llvm/trunk/include/llvm/Use.h Sat Mar 28 23:32:37 2009
@@ -24,11 +24,21 @@
class Value;
class User;
-
+class Use;
/// Tag - generic tag type for (at least 32 bit) pointers
enum Tag { noTag, tagOne, tagTwo, tagThree };
+// Use** is only 4-byte aligned.
+template<>
+class PointerLikeTypeTraits<Use**> {
+public:
+ static inline void *getAsVoidPointer(Use** P) { return P; }
+ static inline Use **getFromVoidPointer(void *P) {
+ return static_cast<Use**>(P);
+ }
+ enum { NumLowBitsAvailable = 2 };
+};
//===----------------------------------------------------------------------===//
// Use Class
@@ -212,7 +222,7 @@
template<> struct simplify_type<const value_use_iterator<const User> >
: public simplify_type<value_use_iterator<const User> > {};
-
+
} // End llvm namespace
#endif
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