<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal>I’m noticing the X86InstrInfo::GetInstSizeInBytes() function
returning incorrect sizes for some instructions. I looked through the llvm-dev
archives and noticed that a patch was submitted once in April 2009 for
instruction length calculation on amd-64. I’m using Intel Core 2 Duo
(64 bit) so maybe there is a similar issue? I don’t have another computer
I can test this on to see if that’s it though. If this turns out to
be a bug, rather than some misuse/misinterpretation of the function on my part
I can resubmit it via that channel. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The instructions I’ve noticed this occurring for are: <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>MOV32mi, LEA32r, MOV32mr, and MOV32rm <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The length of LEA32r is calculated correctly some of the
time. Same for MOV32mr and MOV32rm. The length of MOV32mi seems to
always be wrong.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>An example breakdown of emitted Machine Instructions –
the machine instructions are those outputted when I pass the -debug
option to lli.exe (formatted by me for readability, left to right):<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>8d 9c 24 30 0a 00 00 LEA32r calculated
length: 7 ok<o:p></o:p></p>
<p class=MsoNormal>8d 6c 24 28 LEA32r calculated
length: 7 incorrect<o:p></o:p></p>
<p class=MsoNormal>8b 86 24 0a 39 00 MOV32rm calculated
length: 6 ok<o:p></o:p></p>
<p class=MsoNormal>8b 44 24 10 MOV32rm calculated
length: 7 incorrect<o:p></o:p></p>
<p class=MsoNormal>89 84 24 34 14 00 00 MOV32mr calculated
length: 7 ok<o:p></o:p></p>
<p class=MsoNormal>89 2c 24 MOV32mr calculated
length: 7 incorrect<o:p></o:p></p>
<p class=MsoNormal>c7 44 24 08 08 0a 00 00 MOV32mi calculated
length: 11 incorrect<o:p></o:p></p>
<p class=MsoNormal>c7 04 24 20 00 38 00 MOV32mi calculated
length: 11 incorrect <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>If more information is needed let me know and I’ll send
it. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thank you in advance and best regards, <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>John Butterworth<o:p></o:p></p>
</div>
</body>
</html>