49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
//===-- lib/floatsidf.c - integer -> double-precision conversion --*- C -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements integer to double-precision conversion for the
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// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
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// mode.
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//
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//===----------------------------------------------------------------------===//
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#define DOUBLE_PRECISION
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#include "fp_lib.h"
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fp_t __floatsidf(int a) {
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const int aWidth = sizeof a * CHAR_BIT;
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// Handle zero as a special case to protect clz
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if (a == 0)
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return fromRep(0);
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// All other cases begin by extracting the sign and absolute value of a
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rep_t sign = 0;
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if (a < 0) {
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sign = signBit;
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a = -a;
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}
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// Exponent of (fp_t)a is the width of abs(a).
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const int exponent = (aWidth - 1) - __builtin_clz(a);
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rep_t result;
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// Shift a into the significand field and clear the implicit bit. Extra
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// cast to unsigned int is necessary to get the correct behavior for
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// the input INT_MIN.
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const int shift = significandBits - exponent;
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result = (rep_t)(unsigned int)a << shift ^ implicitBit;
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// Insert the exponent
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result += (rep_t)(exponent + exponentBias) << significandBits;
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// Insert the sign bit and return
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return fromRep(result | sign);
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}
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