ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Application Level Programmers’ Model
The following functions perform conversions between single-precision and double-precision floating-point
numbers.
// FPSingleToDouble()
// ==================
bits(64) FPSingleToDouble(bits(32) operand, boolean fpscr_controlled)
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
(type,sign,value) = FPUnpack(operand, fpscr_val);
if type == FPType_SNaN || type == FPType_QNaN then
if fpscr_val == ‘1’ then // DN bit set
result = FPDefaultNaN(64);
else
result = sign : ‘11111111111 1’ : operand : Zeros(29);
if type == FPType_SNaN then
FPProcessException(FPExc_InvalidOp, fpscr_val);
elsif type = FPType_Infinity then
result = FPInfinity(sign, 64);
elsif type = FPType_Zero then
result = FPZero(sign, 64);
else
result = FPRound(value, 64, fpscr_val); // Rounding will be exact
return result;
// FPDoubleToSingle()
// ==================
bits(32) FPDoubleToSingle(bits(64) operand, boolean fpscr_controlled)
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
(type,sign,value) = FPUnpack(operand, fpscr_val);
if type == FPType_SNaN || type == FPType_QNaN then
if fpscr_val == ‘1’ then // DN bit set
result = FPDefaultNaN(32);
else
result = sign : ‘11111111 1’ : operand;
if type == FPType_SNaN then
FPProcessException(FPExc_InvalidOp, fpscr_val);
elsif type = FPType_Infinity then
result = FPInfinity(sign, 32);
elsif type = FPType_Zero then
result = FPZero(sign, 32);
else
result = FPRound(value, 32, fpscr_val);
return result;
The following functions perform conversions between floating-point numbers and integers or fixed-point
numbers:
// FPToFixed()
// ===========
bits(M) FPToFixed(bits(N) operand, integer M, integer fraction_bits, boolean unsigned,
boolean round_towards_zero, boolean fpscr_controlled)
assert N == 32 || N == 64;
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. A2-65