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llvm-mirror/lib/Support/APSInt.cpp
Alex Lorenz 80dea2fad8 ADT: Add a string APSInt constructor.
This commit moves the APSInt initialization code that's used by
the LLLexer class into a new APSInt constructor that constructs
APSInts from strings.

This change is useful for MIR Serialization, as it would allow
the MILexer class to use the same APSInt initialization as 
LLexer when parsing immediate machine operands.

llvm-svn: 240436
2015-06-23 18:22:10 +00:00

43 lines
1.4 KiB
C++

//===-- llvm/ADT/APSInt.cpp - Arbitrary Precision Signed Int ---*- C++ -*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the APSInt class, which is a simple class that
// represents an arbitrary sized integer that knows its signedness.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/FoldingSet.h"
using namespace llvm;
APSInt::APSInt(StringRef Str) {
assert(!Str.empty() && "Invalid string length");
// (Over-)estimate the required number of bits.
unsigned NumBits = ((Str.size() * 64) / 19) + 2;
APInt Tmp(NumBits, Str, /*Radix=*/10);
if (Str[0] == '-') {
unsigned MinBits = Tmp.getMinSignedBits();
if (MinBits > 0 && MinBits < NumBits)
Tmp = Tmp.trunc(MinBits);
*this = APSInt(Tmp, /*IsUnsigned=*/false);
return;
}
unsigned ActiveBits = Tmp.getActiveBits();
if (ActiveBits > 0 && ActiveBits < NumBits)
Tmp = Tmp.trunc(ActiveBits);
*this = APSInt(Tmp, /*IsUnsigned=*/true);
}
void APSInt::Profile(FoldingSetNodeID& ID) const {
ID.AddInteger((unsigned) (IsUnsigned ? 1 : 0));
APInt::Profile(ID);
}