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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">sgv stands for string global variable, and is a string to represent certain attributes in LLVM-IR. This is fairly ancient and in the future we will be using named metadata/metadata
nodes. You can look at AMDILModuleInfo.cpp:parseSGV to see what the string can contain, but for most cases, it can be a zero initialized array of i8 of size 1. FGV stores the filename.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">LVGV stores information about local arrays that are declared at the kernel scope in OpenCL.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><br>
So, basically the structure looks like this:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">struct {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">const char* kernel;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">const char* sgv;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">const char* fgv;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">const char* lvgv;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">unsigned kernel#;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">} llvm_global_annotations a[].<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">If you encode your function name with __OpenCL_<name>_kernel, it should trigger code generation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Also, we do not use clang for our frontend, so I'm not sure how it would generate code.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Micah<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></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""> Daniels, Marcus G [mailto:mdaniels@lanl.gov]
<br>
<b>Sent:</b> Tuesday, December 13, 2011 1:34 PM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> LLVM Developers Mailing List<br>
<b>Subject:</b> Re: [LLVMdev] AMD IL Code Generator Backend for OpenCL<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Micah, all, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Dec 13, 2011, at 8:49 AM, Villmow, Micah wrote:<o:p></o:p></p>
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<p class="MsoNormal"><br>
<br>
<o:p></o:p></p>
<p class="MsoNormal"><span class="apple-style-span"><span style="font-size:11.5pt;font-family:"Calibri","sans-serif"">If you look at the test cases, you can infer what needs to be done. Basically since this is targeted</span></span><span class="apple-style-span">
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">for OpenCL, we annotate OpenCL kernels slightly different than normal functions and that is</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">what causes the code to be generated. That being said, on my list of things to do is fix this so that</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">any function will be generated correctly and also create calling conventions that differentiate</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">between kernels and non-kernels.</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">`triple.ll' in your patch has this metadata, but I can't see how to construct it with clang..<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">%0 = type { i8*, i8*, i8*, i8*, i32 }<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">@sgv = internal addrspace(2) constant [1 x i8] zeroinitializer<o:p></o:p></p>
</div>
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<p class="MsoNormal">@fgv = internal addrspace(2) constant [1 x i8] zeroinitializer<o:p></o:p></p>
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<p class="MsoNormal">@lvgv = internal constant [0 x i8*] zeroinitializer<o:p></o:p></p>
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<p class="MsoNormal">@llvm.global.annotations = appending global [1 x %0] [%0 { i8* bitcast (void ()* @__OpenCL_foo_kernel to i8*), i8* bitcast ([1 x i8] addrspace(2)* @sgv to i8*), i8* bitcast ([1 x i8] addrspace(2)* @fgv to i8*), i8* bitcast ([0 x i8*]* @lvgv
to i8*), i32 0 }], section "llvm.metadata"<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">define void @__OpenCL_foo_kernel() nounwind readnone {<o:p></o:p></p>
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<p class="MsoNormal">entry:<o:p></o:p></p>
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<p class="MsoNormal"> ret void<o:p></o:p></p>
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<div>
<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Here's my attempt.. I'm guessing that __kernel in OpenCL triggers your annotation, but when I try to use annotate("doesNothing") there's no sign of "doesNothing" in the resulting IR.<o:p></o:p></p>
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<p class="MsoNormal">Thus, my attempt with the function pointers. %0 still has a different form, however.<o:p></o:p></p>
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<p class="MsoNormal">What do "sgv" and "fgv" stand for? Stack & Frame? The semantics of these isn't obvious from the test cases.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
</div>
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<div>
<div>
<div>
<p class="MsoNormal">$ cat a.c<o:p></o:p></p>
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<p class="MsoNormal">static const char __attribute__ ((address_space(2))) sgv[1];<o:p></o:p></p>
</div>
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<p class="MsoNormal">static const char __attribute__ ((address_space(2))) fgv[1];<o:p></o:p></p>
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<p class="MsoNormal">static const char* lvgv[0];<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">void __attribute__ ((annotate("doesNothing"))) func () {<o:p></o:p></p>
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<p class="MsoNormal"> char val;<o:p></o:p></p>
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<p class="MsoNormal"> val = sgv[0];<o:p></o:p></p>
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<p class="MsoNormal"> val = fgv[0];<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> val = *lvgv[0];<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">}<o:p></o:p></p>
</div>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">void __attribute__ ((annotate("foobar"))) (*__OpenCL_my_kernel) () = func;<o:p></o:p></p>
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<div>
<p class="MsoNormal">$ clang -S -emit-llvm a.c<o:p></o:p></p>
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<div>
<p class="MsoNormal">$ cat a.s<o:p></o:p></p>
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<p class="MsoNormal">; ModuleID = 'a.c'<o:p></o:p></p>
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<p class="MsoNormal">target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"<o:p></o:p></p>
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<p class="MsoNormal">target triple = "x86_64-unknown-linux-gnu"<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">%0 = type { i8*, i8*, i8*, i32 }<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">@sgv = internal addrspace(2) constant [1 x i8] zeroinitializer, align 1<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">@fgv = internal addrspace(2) constant [1 x i8] zeroinitializer, align 1<o:p></o:p></p>
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<p class="MsoNormal">@lvgv = internal global [0 x i8*] zeroinitializer, align 8<o:p></o:p></p>
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<p class="MsoNormal">@__OpenCL_my_kernel = global void (...)* bitcast (void ()* @func to void (...)*), align 8<o:p></o:p></p>
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<p class="MsoNormal">@__OpenCL_my_kernel1 = private global [7 x i8] c"foobar\00"<o:p></o:p></p>
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<p class="MsoNormal">@.str = private unnamed_addr global [4 x i8] c"a.c\00"<o:p></o:p></p>
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<p class="MsoNormal">@llvm.global.annotations = appending global [1 x %0] [%0 { i8* bitcast (void (...)** @__OpenCL_my_kernel to i8*), i8* getelementptr inbounds ([7 x i8]* @__OpenCL_my_kernel1, i32 0, i32 0), i8* getelementptr inbounds ([4 x i8]* @.str, i32
0, i32 0), i32 12 }], section "llvm.metadata"<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">define void @func() nounwind {<o:p></o:p></p>
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<div>
<p class="MsoNormal"> %val = alloca i8, align 1<o:p></o:p></p>
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<p class="MsoNormal"> %1 = load i8 addrspace(2)* getelementptr inbounds ([1 x i8] addrspace(2)* @sgv, i32 0, i64 0)<o:p></o:p></p>
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<div>
<p class="MsoNormal"> store i8 %1, i8* %val, align 1<o:p></o:p></p>
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<p class="MsoNormal"> %2 = load i8 addrspace(2)* getelementptr inbounds ([1 x i8] addrspace(2)* @fgv, i32 0, i64 0)<o:p></o:p></p>
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<p class="MsoNormal"> store i8 %2, i8* %val, align 1<o:p></o:p></p>
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<p class="MsoNormal"> %3 = load i8** getelementptr inbounds ([0 x i8*]* @lvgv, i32 0, i64 0)<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> %4 = load i8* %3<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> store i8 %4, i8* %val, align 1<o:p></o:p></p>
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<p class="MsoNormal"> ret void<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal">Adding "__kernel" to "func" does create some metadata when clang is in OpenCL mode, and the IR looks like this:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">!opencl.kernels = !{!0}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">!0 = metadata !{void ()* @func}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Cheers,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Marcus<o:p></o:p></p>
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