<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 14 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 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;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></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="WordSection1">
<p class="MsoNormal">The module.modulemap has the two module entries:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> explicit module sse4_1 {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> requires sse41<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> export ssse3<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> header "smmintrin.h"<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> explicit module sse4_2 {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> requires sse42<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> export sse4_1<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> header "nmmintrin.h"<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Consolas;color:black;background:white;mso-highlight:white"> }<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, “sse41” and “sse42” in the requires don’t match the “sse4.1” and “sse4.2” target features. This leads to error messages like:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">4.cpp:5:12: error: call to '_mm_blendv_ps' is ambiguous<o:p></o:p></p>
<p class="MsoNormal"> return _mm_blendv_ps(x,y,z);<o:p></o:p></p>
<p class="MsoNormal"> ^~~~~~~~~~~~~<o:p></o:p></p>
<p class="MsoNormal">...\lib\clang\include\smmintrin.h:103:1: note: candidate function<o:p></o:p></p>
<p class="MsoNormal">_mm_blendv_ps (__m128 __V1, __m128 __V2, __m128 __M)<o:p></o:p></p>
<p class="MsoNormal">^<o:p></o:p></p>
<p class="MsoNormal">...\lib\clang\include\smmintrin.h:103:1: note: candidate function<o:p></o:p></p>
<p class="MsoNormal">_mm_blendv_ps (__m128 __V1, __m128 __V2, __m128 __M)<o:p></o:p></p>
<p class="MsoNormal">^<o:p></o:p></p>
<p class="MsoNormal">1 error generated.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Because the ‘.’ makes the requires name an invalid identifier, either the feature name needs to change, or there needs to be some kinds of mapping or substitution done. For example, I understand changing the feature name might be problematic,
so changing the module map to use “sse4_1” and have clang replace the ‘_’ with ‘.’ before the feature check, or just map the problematic names, or decouple the “requires” names from the features names, are some possible options. What do you think?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">But also, this raises another issue. The reason I get the error is because the compiler silently failed to match the requires argument, but went ahead and processed the header textually or something, leading to the confusing error. Could
we improve the error detection here? Are there other situations where a silent failure is problematic?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Perhaps make the hasFeature return a three-state value with one that will indicate invalid feature name?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-John<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>