TruthTable.cpp File Reference

#include "circt/Support/TruthTable.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <cassert>

Include dependency graph for TruthTable.cpp:

Go to the source code of this file.

Functions
template<bool positive>
static APInt	createVarMaskImpl (unsigned numVars, unsigned varIndex)
	Create a mask for a variable in the truth table.

Variables
static constexpr uint64_t	kVarMasks [2][6]
	Precomputed masks for variables in truth tables up to 6 variables (64 bits).

Function Documentation

createVarMaskImpl()

template<bool positive>

static APInt createVarMaskImpl ( unsigned  numVars, unsigned  varIndex  )

static

Create a mask for a variable in the truth table.

For positive=true: mask has 1s where var=1 in the truth table encoding For positive=false: mask has 1s where var=0 in the truth table encoding

Definition at line 299 of file TruthTable.cpp.

References assert(), kVarMasks, and pattern.

Variable Documentation

kVarMasks

constexpr uint64_t kVarMasks[2][6]

staticconstexpr

Initial value:

= {
    {0x5555555555555555ULL, 0x3333333333333333ULL, 0x0F0F0F0F0F0F0F0FULL,
     0x00FF00FF00FF00FFULL, 0x0000FFFF0000FFFFULL,
     0x00000000FFFFFFFFULL}, 
    {0xAAAAAAAAAAAAAAAAULL, 0xCCCCCCCCCCCCCCCCULL, 0xF0F0F0F0F0F0F0F0ULL,
     0xFF00FF00FF00FF00ULL, 0xFFFF0000FFFF0000ULL,
     0xFFFFFFFF00000000ULL}, 
}

Precomputed masks for variables in truth tables up to 6 variables (64 bits).

In a truth table, bit position i represents minterm i, where the binary representation of i gives the variable values. For example, with 3 variables (a,b,c), bit 5 (binary 101) represents minterm a=1, b=0, c=1.

These masks identify which minterms have a particular variable value:

• Masks[0][var] = minterms where var=0 (for negative literal !var)
• Masks[1][var] = minterms where var=1 (for positive literal var)

Definition at line 286 of file TruthTable.cpp.

Referenced by createVarMaskImpl().