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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Back in the day, we called this a BLT (block transfer, pronouced 'blit') for the PDP-10 instruction of that name.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You can do this by assigning the first value, then do an overlapping memcpy to fill in the rest.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">There's probably something clever you can do with vector instructions too, in many cases.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></a></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> llvm-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Ryan Taylor via llvm-dev<br>
<b>Sent:</b> Thursday, November 10, 2016 2:08 PM<br>
<b>To:</b> Bagel; llvm-dev<br>
<b>Subject:</b> Re: [llvm-dev] array fill idioms<o:p></o:p></span></p>
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<p class="MsoNormal">Like a list initializer, but will do partials/slices?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Are you just looking to create an intrinsic that will generate a jump to a lib routine? <o:p></o:p></p>
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<p class="MsoNormal">On Thu, Nov 10, 2016 at 5:02 PM, Bagel via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Yes, I know this works peachy keen for char arrays. I'm looking at (which is<br>
hard to express in C) something like<br>
<br>
void foo () {<br>
int bar[20] = { 42, 42, ..., 42 };<br>
}<br>
<br>
I don't want to do a memcopy of the 20 element constant array, and memset<br>
doesn't work here. I want an intrinsic that copys the scalar int constant 42<br>
to each element of the int array.<br>
<span style="color:#888888"><br>
<span class="hoenzb">bagel</span><br>
</span><br>
<br>
<span class="im">On 11/10/2016 03:30 PM, Mehdi Amini wrote:</span><br>
<span class="im">> Hi,</span><br>
<span class="im">></span><br>
<span class="im">> An alternative is to perform what is done for the equivalent C construct:</span><br>
<span class="im">></span><br>
<span class="im">> void foo() {</span><br>
<span class="im">> char bar[20] = “hello”;</span><br>
<span class="im">> }</span><br>
<span class="im">></span><br>
<span class="im">> -></span><br>
<span class="im">></span><br>
<span class="im">> @foo.bar = private unnamed_addr constant [20 x i8] c"hello\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00", align 16</span><br>
<span class="im">> define void @foo() #0 {</span><br>
<span class="im">> %1 = alloca [20 x i8], align 16</span><br>
<span class="im">> %2 = bitcast [20 x i8]* %1 to i8*</span><br>
<span class="im">> call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* getelementptr inbounds ([20 x i8], [20 x i8]* @foo.bar, i32 0, i32 0), i64 20, i32 16, i1 false)</span><br>
<span class="im">> ret void</span><br>
<span class="im">> }</span><br>
<span class="im">></span><br>
<span class="im">></span><br>
<span class="im">> —</span><br>
<span class="im">> Mehdi</span><o:p></o:p></p>
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<p class="MsoNormal">_______________________________________________<br>
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