forked from NRZCode/ia32-64
81 lines
3.6 KiB
HTML
81 lines
3.6 KiB
HTML
<!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>BLSR
|
||
— Reset Lowest Set Bit</title></head><body><header><nav><ul><li><a href='index.html'>Index</a></li><li>December 2023</li></ul></nav></header><h1>BLSR
|
||
— Reset Lowest Set Bit</h1>
|
||
|
||
<table>
|
||
<tr>
|
||
<th>Opcode/Instruction</th>
|
||
<th>Op/En</th>
|
||
<th>64/32-bit Mode</th>
|
||
<th>CPUID Feature Flag</th>
|
||
<th>Description</th></tr>
|
||
<tr>
|
||
<td>VEX.LZ.0F38.W0 F3 /1 BLSR r32, r/m32</td>
|
||
<td>VM</td>
|
||
<td>V/V</td>
|
||
<td>BMI1</td>
|
||
<td>Reset lowest set bit of r/m32, keep all other bits of r/m32 and write result to r32.</td></tr>
|
||
<tr>
|
||
<td>VEX.LZ.0F38.W1 F3 /1 BLSR r64, r/m64</td>
|
||
<td>VM</td>
|
||
<td>V/N.E.</td>
|
||
<td>BMI1</td>
|
||
<td>Reset lowest set bit of r/m64, keep all other bits of r/m64 and write result to r64.</td></tr></table>
|
||
<h2 id="instruction-operand-encoding">Instruction Operand Encoding<a class="anchor" href="#instruction-operand-encoding">
|
||
¶
|
||
</a></h2>
|
||
<table>
|
||
<tr>
|
||
<th>Op/En</th>
|
||
<th>Operand 1</th>
|
||
<th>Operand 2</th>
|
||
<th>Operand 3</th>
|
||
<th>Operand 4</th></tr>
|
||
<tr>
|
||
<td>VM</td>
|
||
<td>VEX.vvvv (w)</td>
|
||
<td>ModRM:r/m (r)</td>
|
||
<td>N/A</td>
|
||
<td>N/A</td></tr></table>
|
||
<h2 id="description">Description<a class="anchor" href="#description">
|
||
¶
|
||
</a></h2>
|
||
<p>Copies all bits from the source operand to the destination operand and resets (=0) the bit position in the destination operand that corresponds to the lowest set bit of the source operand. If the source operand is zero BLSR sets CF.</p>
|
||
<p>This instruction is not supported in real mode and virtual-8086 mode. The operand size is always 32 bits if not in 64-bit mode. In 64-bit mode operand size 64 requires VEX.W1. VEX.W1 is ignored in non-64-bit modes. An attempt to execute this instruction with VEX.L not equal to 0 will cause #UD.</p>
|
||
<h2 id="operation">Operation<a class="anchor" href="#operation">
|
||
¶
|
||
</a></h2>
|
||
<pre>temp := (SRC-1) bitwiseAND ( SRC );
|
||
SF := temp[OperandSize -1];
|
||
ZF := (temp = 0);
|
||
IF SRC = 0
|
||
CF := 1;
|
||
ELSE
|
||
CF := 0;
|
||
FI
|
||
DEST := temp;
|
||
</pre>
|
||
<h2 id="flags-affected">Flags Affected<a class="anchor" href="#flags-affected">
|
||
¶
|
||
</a></h2>
|
||
<p>ZF and SF flags are updated based on the result. CF is set if the source is zero. OF flag is cleared. AF and PF flags are undefined.</p>
|
||
<h2 id="intel-c-c++-compiler-intrinsic-equivalent">Intel C/C++ Compiler Intrinsic Equivalent<a class="anchor" href="#intel-c-c++-compiler-intrinsic-equivalent">
|
||
¶
|
||
</a></h2>
|
||
<pre>BLSR unsigned __int32 _blsr_u32(unsigned __int32 src);
|
||
</pre>
|
||
<pre>BLSR unsigned __int64 _blsr_u64(unsigned __int64 src);
|
||
</pre>
|
||
<h2 class="exceptions" id="simd-floating-point-exceptions">SIMD Floating-Point Exceptions<a class="anchor" href="#simd-floating-point-exceptions">
|
||
¶
|
||
</a></h2>
|
||
<p>None.</p>
|
||
<h2 class="exceptions" id="other-exceptions">Other Exceptions<a class="anchor" href="#other-exceptions">
|
||
¶
|
||
</a></h2>
|
||
<p>See <span class="not-imported">Table 2-29</span>, “Type 13 Class Exception Conditions.”</p><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>
|