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

Maximum and minimum
// FPMax()
// =======
Application Level Programmers’ Model
bits(N) FPMax(bits(N) op1, bits(N) op2, boolean fpscr_controlled)
assert N == 32 || N == 64;
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
(type1,sign1,value1) = FPUnpack(op1, fpscr_val);
(type2,sign2,value2) = FPUnpack(op2, fpscr_val);
(done,result) = FPProcessNaNs(type1, type2, op1, op2, fpscr_val);
if !done then
if type1 == FPType_Zero && type2 == FPType_Zero && sign1 == NOT(sign2) then
// Opposite-signed zeros produce +0.0
result = FPZero(‘0’, N);
else
// All other cases can be evaluated on the values produced by FPUnpack()
result = if value1 > value2 then op1 else op2;
return result;
// FPMin()
// =======
bits(N) FPMin(bits(N) op1, bits(N) op2, boolean fpscr_controlled)
assert N == 32 || N == 64;
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
(type1,sign1,value1) = FPUnpack(op1, fpscr_val);
(type2,sign2,value2) = FPUnpack(op2, fpscr_val);
(done,result) = FPProcessNaNs(type1, type2, op1, op2, fpscr_val);
if !done then
if type1 == FPType_Zero && type2 == FPType_Zero && sign1 == NOT(sign2) then
// Opposite-signed zeros produce -0.0
result = FPZero(‘1’, N);
else
// All other cases can be evaluated on the values produced by FPUnpack()
result = if value1 < value2 then op1 else op2;
return result;
Addition and subtraction
// FPAdd()
// =======
bits(N) FPAdd(bits(N) op1, bits(N) op2, boolean fpscr_controlled)
assert N == 32 || N == 64;
fpscr_val = if fpscr_controlled then FPSCR else StandardFPSCRValue();
(type1,sign1,value1) = FPUnpack(op1, fpscr_val);
(type2,sign2,value2) = FPUnpack(op2, fpscr_val);
(done,result) = FPProcessNaNs(type1, type2, op1, op2, fpscr_val);
if !done then
inf1 = (type1 == FPType_Infinity); inf2 = (type2 == FPType_Infinity);
zero1 = (type1 == FPType_Zero); zero2 = (type2 == FPType_Zero);
if inf1 && inf2 && sign1 == NOT(sign2) then
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. A2-55