Differential D2174 Diff 4509 contrib/compiler-rt/lib/builtins/floatditf.c

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contrib/compiler-rt/lib/builtins/floatditf.c

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				//===-- lib/floatditf.c - integer -> quad-precision conversion ----- C --===//
				//
				// The LLVM Compiler Infrastructure
				//
				// This file is dual licensed under the MIT and the University of Illinois Open
				// Source Licenses. See LICENSE.TXT for details.
				//
				//===----------------------------------------------------------------------===//
				//
				// This file implements di_int to quad-precision conversion for the
				// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
				// mode.
				edUnsubmitted Not Done Inline Actions Out of curiosity, is this also what this function is supposed to do unconditionally? These functions are not supposed to integrate with `fegetround()` / `FLT_ROUNDS`? ed: Out of curiosity, is this also what this function is supposed to do unconditionally? These…
				emasteAuthorUnsubmitted Not Done Inline Actions Good question; this was inherited from the floatsitf function I started from. The thread I started on llvmdev is here: http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-March/084064.html emaste: Good question; this was inherited from the floatsitf function I started from. The thread I…
				//
				//===----------------------------------------------------------------------===//

				#define QUAD_PRECISION
				#include "fp_lib.h"

				#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
				COMPILER_RT_ABI fp_t __floatditf(di_int a) {

				const int aWidth = sizeof a * CHAR_BIT;

				// Handle zero as a special case to protect clz
				if (a == 0)
				return fromRep(0);

				// All other cases begin by extracting the sign and absolute value of a
				rep_t sign = 0;
				unsigned aAbs = (unsigned)a;
				if (a < 0) {
				sign = signBit;
				aAbs += 0x80000000;
				}

				// Exponent of (fp_t)a is the width of abs(a).
				const int exponent = (aWidth - 1) - __builtin_clz(a);
				rep_t result;

				// Shift a into the significand field and clear the implicit bit. Extra
				// cast to unsigned int is necessary to get the correct behavior for
				// the input INT_MIN.
				const int shift = significandBits - exponent;
				result = (rep_t)aAbs << shift ^ implicitBit;

				// Insert the exponent
				result += (rep_t)(exponent + exponentBias) << significandBits;
				edUnsubmitted Not Done Inline Actions These functions do not support subnormal floating point numbers. Should this be implemented, or at least documented? ed: These functions do not support subnormal floating point numbers. Should this be implemented, or…
				emasteAuthorUnsubmitted Not Done Inline Actions I'm missing something - how would you implement int to subnormal float conversion? emaste: I'm missing something - how would you implement int to subnormal float conversion?
				edUnsubmitted Not Done Inline Actions D'oh. Just ignore that question. We're only interested in generating integers, of course. :-) ed: D'oh. Just ignore that question. We're only interested in generating integers, of course. :-)
				// Insert the sign bit and return
				return fromRep(result \| sign);
				}

				#endif