12 <concept id="GUID-5E358AB4-03A7-5859-ABF2-A8B64B74AF56" xml:lang="en"><title>Vector

    12 <concept id="GUID-5E358AB4-03A7-5859-ABF2-A8B64B74AF56" xml:lang="en"><title>Vector Floating Point Architecture (VFP)</title><shortdesc>Describes the implementation of the ARM Vector Floating

    13 Floating Point Architecture (VFP)</title><shortdesc>Describes the implementation of the ARM Vector Floating Point Architecture

    13 Point Architecture (VFPv2) on Symbian platform. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 (VFPv2) on Symbian platform. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>ARM provide a hardware floating point coprocessor that provides

    15 <p>ARM provide a hardware floating point coprocessor that provides floating

    15 floating point computation that is fully compliant with IEEE Std 754-1985.We

    16 point computation that is fully compliant with IEEE Std 754-1985.We refer

    16 refer to the coprocessor as the <i>VFP unit</i>. </p>

    17 to the coprocessor as the <i>VFP unit</i>. </p>

    17 <p>Symbian platform supports the use of VFPv2 on platforms where the

    18 <p>Symbian platform supports the use of VFPv2 on platforms where the required

    18 required hardware is present in both <i>RunFast</i> mode and in <i>IEEE-without-exceptions</i> mode. See ARM's Vector Floating-point

    19 hardware is present in both <i>RunFast</i> mode and in <i>IEEE-without-exceptions</i> mode.

    19 Coprocessor Technical reference Manual for more details on the coprocessor,

    20 See ARM's Vector Floating-point Coprocessor Technical reference Manual for

    20 its architecture, and its execution modes. </p>

    21 more details on the coprocessor, its architecture, and its execution modes. </p>

    21 <p>You should read Floating point support in Symbian^3 Tools Guide

    22 <p>You should read the information in <xref href="GUID-D525B9A9-6B32-535B-A282-60C85A48D3FB.dita">Floating

    22 > Building. The guide contains information about applications and

    23 point support</xref> about applications and user side code as this is also

    23 user-side code, which is also applicable to code running

    24 applicable to code running on the kernel side. However there are a number

    24 on the kernel side. However there are a number of restrictions that

    25 of restrictions that must be observed: </p>

    25 must be observed: </p>

    27 <li id="GUID-2205026D-0E6F-54AE-B74F-5478D6047B70"><p>You <i>cannot</i> use

    27 <li id="GUID-2205026D-0E6F-54AE-B74F-5478D6047B70"><p>You <i>cannot</i> use VFP instructions in any interrupt service routine. </p> </li>

    28 VFP instructions in any interrupt service routine. </p> </li>

    28 <li id="GUID-C8D896E1-CF36-52CD-A984-61D7A8189268"><p>You <i>cannot</i> use VFP instructions when the kernel is locked, for example, in

    29 <li id="GUID-C8D896E1-CF36-52CD-A984-61D7A8189268"><p>You <i>cannot</i> use

    29 an IDFC or after calling <xref href="GUID-3A3C08F3-3D33-3D9E-80E7-7855C7B21E02.dita#GUID-3A3C08F3-3D33-3D9E-80E7-7855C7B21E02/GUID-7CBBF72B-4519-38DD-92CA-38AF636AFD8A"><apiname>NKern::Lock()</apiname></xref>  </p> </li>

    30 VFP instructions when the kernel is locked, for example, in an IDFC or after

    30 <li id="GUID-A7466A83-A8F2-58CE-AB8B-E05607BB6D95"><p>You <i>cannot</i> use VFP instructions in any section of code which runs with a fast

    31 calling <xref href="GUID-3A3C08F3-3D33-3D9E-80E7-7855C7B21E02.dita#GUID-3A3C08F3-3D33-3D9E-80E7-7855C7B21E02/GUID-7CBBF72B-4519-38DD-92CA-38AF636AFD8A"><apiname>NKern::Lock()</apiname></xref>  </p> </li>

    31 mutex held. </p> </li>

    32 <li id="GUID-A7466A83-A8F2-58CE-AB8B-E05607BB6D95"><p>You <i>cannot</i> use

    33 VFP instructions in any section of code which runs with a fast mutex held. </p> </li>

    35 <p>Using VFP instructions in these situations can lead to data being corrupted,

    33 <p>Using VFP instructions in these situations can lead to data being

    36 or the kernel panicking. If you rely on the compiler to generate VFP instructions,

    34 corrupted, or the kernel panicking. If you rely on the compiler to

    37 rather than using inline assembler, it is extremely important that you do

    35 generate VFP instructions, rather than using inline assembler, it

    38 not use any floating point values in these situations. The compiler may generate

    36 is extremely important that you do not use any floating point values

    39 VFP instructions for the most trivial floating point operations and even for

    37 in these situations. The compiler may generate VFP instructions for

    40 simple assignments. </p>

    38 the most trivial floating point operations and even for simple assignments. </p>