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<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:svg="http://www.w3.org/2000/svg" xmlns:x86="http://www.felixcloutier.com/x86"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><link rel="stylesheet" type="text/css" href="style.css"></link><title>FLD
— Load Floating-Point Value</title></head><body><header><nav><ul><li><a href='index.html'>Index</a></li><li>December 2023</li></ul></nav></header><h1>FLD
— Load Floating-Point Value</h1>
<table>
<tr>
<th>Opcode</th>
<th>Instruction</th>
<th>64-Bit Mode</th>
<th>Compat/Leg Mode</th>
<th>Description</th></tr>
<tr>
<td>D9 /0</td>
<td>FLD m32fp</td>
<td>Valid</td>
<td>Valid</td>
<td>Push m32fp onto the FPU register stack.</td></tr>
<tr>
<td>DD /0</td>
<td>FLD m64fp</td>
<td>Valid</td>
<td>Valid</td>
<td>Push m64fp onto the FPU register stack.</td></tr>
<tr>
<td>DB /5</td>
<td>FLD m80fp</td>
<td>Valid</td>
<td>Valid</td>
<td>Push m80fp onto the FPU register stack.</td></tr>
<tr>
<td>D9 C0+i</td>
<td>FLD ST(i)</td>
<td>Valid</td>
<td>Valid</td>
<td>Push ST(i) onto the FPU register stack.</td></tr></table>
<h2 id="description">Description<a class="anchor" href="#description">
</a></h2>
<p>Pushes the source operand onto the FPU register stack. The source operand can be in single precision, double precision, or double extended-precision floating-point format. If the source operand is in single precision or double precision floating-point format, it is automatically converted to the double extended-precision floating-point format before being pushed on the stack.</p>
<p>The FLD instruction can also push the value in a selected FPU register [ST(i)] onto the stack. Here, pushing register ST(0) duplicates the stack top.</p>
<blockquote>
<p>When the FLD instruction loads a denormal value and the DM bit in the CW is not masked, an exception is flagged but the value is still pushed onto the x87 stack.</p></blockquote>
<p>This instruction’s operation is the same in non-64-bit modes and 64-bit mode.</p>
<h2 id="operation">Operation<a class="anchor" href="#operation">
</a></h2>
<pre>IF SRC is ST(i)
THEN
temp := ST(i);
FI;
TOP := TOP − 1;
IF SRC is memory-operand
THEN
ST(0) := ConvertToDoubleExtendedPrecisionFP(SRC);
ELSE (* SRC is ST(i) *)
ST(0) := temp;
FI;
</pre>
<h2 id="fpu-flags-affected">FPU Flags Affected<a class="anchor" href="#fpu-flags-affected">
</a></h2>
<table>
<tr>
<td>C1</td>
<td>Set to 1 if stack overflow occurred; otherwise, set to 0.</td></tr>
<tr>
<td>C0, C2, C3</td>
<td>Undefined.</td></tr></table>
<h2 class="exceptions" id="floating-point-exceptions">Floating-Point Exceptions<a class="anchor" href="#floating-point-exceptions">
</a></h2>
<table>
<tr>
<td>#IS</td>
<td>Stack underflow or overflow occurred.</td></tr>
<tr>
<td>#IA</td>
<td>Source operand is an SNaN. Does not occur if the source operand is in double extended-precision floating-point format (FLD m80fp or FLD ST(i)).</td></tr>
<tr>
<td>#D</td>
<td>Source operand is a denormal value. Does not occur if the source operand is in double extended-precision floating-point format.</td></tr></table>
<h2 class="exceptions" id="protected-mode-exceptions">Protected Mode Exceptions<a class="anchor" href="#protected-mode-exceptions">
</a></h2>
<table>
<tr>
<td rowspan="3">#GP(0)</td>
<td>If destination is located in a non-writable segment.</td></tr>
<tr>
<td>If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.</td></tr>
<tr>
<td>If the DS, ES, FS, or GS register is used to access memory and it contains a NULL segment selector.</td></tr>
<tr>
<td>#SS(0)</td>
<td>If a memory operand effective address is outside the SS segment limit.</td></tr>
<tr>
<td>#NM</td>
<td>CR0.EM[bit 2] or CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#AC(0)</td>
<td>If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.</td></tr>
<tr>
<td>#UD</td>
<td>If the LOCK prefix is used.</td></tr></table>
<h2 class="exceptions" id="real-address-mode-exceptions">Real-Address Mode Exceptions<a class="anchor" href="#real-address-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#GP</td>
<td>If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.</td></tr>
<tr>
<td>#SS</td>
<td>If a memory operand effective address is outside the SS segment limit.</td></tr>
<tr>
<td>#NM</td>
<td>CR0.EM[bit 2] or CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#UD</td>
<td>If the LOCK prefix is used.</td></tr></table>
<h2 class="exceptions" id="virtual-8086-mode-exceptions">Virtual-8086 Mode Exceptions<a class="anchor" href="#virtual-8086-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#GP(0)</td>
<td>If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.</td></tr>
<tr>
<td>#SS(0)</td>
<td>If a memory operand effective address is outside the SS segment limit.</td></tr>
<tr>
<td>#NM</td>
<td>CR0.EM[bit 2] or CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#AC(0)</td>
<td>If alignment checking is enabled and an unaligned memory reference is made.</td></tr>
<tr>
<td>#UD</td>
<td>If the LOCK prefix is used.</td></tr></table>
<h2 class="exceptions" id="compatibility-mode-exceptions">Compatibility Mode Exceptions<a class="anchor" href="#compatibility-mode-exceptions">
</a></h2>
<p>Same exceptions as in protected mode.</p>
<h2 class="exceptions" id="64-bit-mode-exceptions">64-Bit Mode Exceptions<a class="anchor" href="#64-bit-mode-exceptions">
</a></h2>
<table>
<tr>
<td>#SS(0)</td>
<td>If a memory address referencing the SS segment is in a non-canonical form.</td></tr>
<tr>
<td>#GP(0)</td>
<td>If the memory address is in a non-canonical form.</td></tr>
<tr>
<td>#NM</td>
<td>CR0.EM[bit 2] or CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#MF</td>
<td>If there is a pending x87 FPU exception.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#AC(0)</td>
<td>If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.</td></tr>
<tr>
<td>#UD</td>
<td>If the LOCK prefix is used.</td></tr></table><footer><p>
This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be
inc<span style="opacity: 0.2">omp</span>lete or b<sub>r</sub>oke<sub>n</sub> in various obvious or non-obvious
ways. Refer to <a href="https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4">Intel® 64 and IA-32 Architectures Software Developer’s Manual</a> for anything serious.
</p></footer></body></html>
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