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<p>Hi Kumail,</p>
<p>There is a flag that does what you are looking for (see
Intrinsics.td for definitions):</p>
<p>// IntrNoduplicate - Calls to this intrinsic cannot be
duplicated.<br>
// Parallels the noduplicate attribute on LLVM IR functions.<br>
def IntrNoDuplicate : IntrinsicProperty;<br>
</p>
<p>Another thing to check is whether your intrinsic is marked as
having side-effects or not. Intrinsics with no side effects may be
optimized by LLVM. If you inspect the DAG using llc, an intrinsic
with side-effects should have a chain (blue dashed edge) going to
and coming from its node:</p>
<p>llc -O1 foo.ll -view-isel-dags<br>
</p>
<p>If it doesn't, you can mark it as having side-effects using one
of the following attributes:<br>
</p>
<p>// IntrReadMem - This intrinsic only reads from memory. It does
not write to<br>
// memory and has no other side effects. Therefore, it cannot be
moved across<br>
// potentially aliasing stores. However, it can be reordered
otherwise and can<br>
// be deleted if dead.<br>
def IntrReadMem : IntrinsicProperty;<br>
<br>
// IntrWriteMem - This intrinsic only writes to memory, but does
not read from<br>
// memory, and has no other side effects. This means dead stores
before calls<br>
// to this intrinsics may be removed.<br>
def IntrWriteMem : IntrinsicProperty;<br>
</p>
By default intrinsics returning void are assumed to have side
effects.<br>
<br>
Pierre-Andre<br>
<br>
<div class="moz-cite-prefix">On 27/01/17 16:33, Kumail Ahmed via
llvm-dev wrote:<br>
</div>
<blockquote
cite="mid:CAEJeK8nD1wR9pn8zVr-vOkCfzftnoY2nEZUoHjpMY_bURzDQZw@mail.gmail.com"
type="cite">
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<div>Hello everyone,<br>
<br>
<br>
</div>
Consider we have this following set of code: <br>
<br>
</div>
int foo() {<br>
<br>
</div>
int a,b;<br>
</div>
a = __builtin_XX(0x11);<br>
</div>
b = __builtin_XX(0x11);<br>
</div>
return a+b;<br>
}<br>
<br>
</div>
The problem currently is that LLVM eliminated the second call
and copied the result from the first call into a new set of
registers. Is there is a way to force LLVM to generate two
explicit calls to a builtin function. The builtin takes in an
integer type, and also returns back an integer type:<br>
<br>
def int_XX : GCCBuiltin<"__builtin_XX">,
Intrinsic<[llvm_i32_ty], [llvm_i32_ty]>;<br>
<br>
</div>
Is there some flag that I'm missing? Your help will be really
appreciated.<br>
<div>
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<div><br>
<br>
<div class="gmail_signature">Best Regards,<br>
Kumail Ahmed<br>
<br>
</div>
</div>
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<br>
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