<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 12, 2015 at 11:16 AM, Duncan P. N. Exon Smith <span dir="ltr"><<a href="mailto:dexonsmith@apple.com" target="_blank">dexonsmith@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
> On 2015-Jan-12, at 11:07, David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br>
><br>
><br>
><br>
> On Wed, Jan 7, 2015 at 1:35 PM, Duncan P. N. Exon Smith <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:<br>
> Author: dexonsmith<br>
> Date: Wed Jan 7 15:35:38 2015<br>
> New Revision: 225401<br>
><br>
> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=225401&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=225401&view=rev</a><br>
> Log:<br>
> IR: Add MDNode::isDistinct()<br>
><br>
> Add API to indicate whether an `MDNode` is distinct. A distinct node is<br>
> not stored in the MDNode uniquing tables, and will never be returned by<br>
> `MDNode::get()`.<br>
><br>
> Although distinct nodes are only currently created by uniquing<br>
> collisions (when operands change),<br>
><br>
> I don't quite understand how changing an operand relates to uniquing collisions - once the operand has changed would we not want the uniquing to happen again? (eg: if changing an operand made this node equal to some other node instead?)<br>
><br>
<br>
</span>It's impossible without RAUW.<br></blockquote><div><br>Even when doing that, it seems strange that it would prevent uniquing - but again, I guess I'm missing something.<br><br>I would sort of expect:<br><br>{1, 2}<br>1 = {a}<br>2 = {b}<br><br>RAUW a -> b<br><br>{2, 2}<br>2 = {b}<br><br>it sort of seems strange to me that the path (directly constructing, versus constructing then RAUWing) to create the value produces a different graph/node/etc?<br><br>- David<br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
> PR22111 will allow these nodes to be<br>
> explicitly created.<br>
><br>
> Modified:<br>
> llvm/trunk/include/llvm/IR/Metadata.h<br>
> llvm/trunk/unittests/IR/MetadataTest.cpp<br>
><br>
> Modified: llvm/trunk/include/llvm/IR/Metadata.h<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Metadata.h?rev=225401&r1=225400&r2=225401&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Metadata.h?rev=225401&r1=225400&r2=225401&view=diff</a><br>
> ==============================================================================<br>
> --- llvm/trunk/include/llvm/IR/Metadata.h (original)<br>
> +++ llvm/trunk/include/llvm/IR/Metadata.h Wed Jan 7 15:35:38 2015<br>
> @@ -642,6 +642,12 @@ public:<br>
> /// \brief Check if node is fully resolved.<br>
> bool isResolved() const;<br>
><br>
> + /// \brief Check if node is distinct.<br>
> + ///<br>
> + /// Distinct nodes are not uniqued, and will not be returned by \a<br>
> + /// MDNode::get().<br>
> + bool isDistinct() const { return IsDistinctInContext; }<br>
> +<br>
> protected:<br>
> /// \brief Set an operand.<br>
> ///<br>
><br>
> Modified: llvm/trunk/unittests/IR/MetadataTest.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/MetadataTest.cpp?rev=225401&r1=225400&r2=225401&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/MetadataTest.cpp?rev=225401&r1=225400&r2=225401&view=diff</a><br>
> ==============================================================================<br>
> --- llvm/trunk/unittests/IR/MetadataTest.cpp (original)<br>
> +++ llvm/trunk/unittests/IR/MetadataTest.cpp Wed Jan 7 15:35:38 2015<br>
> @@ -222,6 +222,33 @@ TEST_F(MDNodeTest, NullOperand) {<br>
> EXPECT_EQ(N, NullOp);<br>
> }<br>
><br>
> +TEST_F(MDNodeTest, DistinctOnUniquingCollision) {<br>
> + // !{}<br>
> + MDNode *Empty = MDNode::get(Context, None);<br>
> + ASSERT_TRUE(Empty->isResolved());<br>
> + EXPECT_FALSE(Empty->isDistinct());<br>
> +<br>
> + // !{!{}}<br>
> + Metadata *Wrapped1Ops[] = {Empty};<br>
> + MDNode *Wrapped1 = MDNode::get(Context, Wrapped1Ops);<br>
> + ASSERT_EQ(Empty, Wrapped1->getOperand(0));<br>
> + ASSERT_TRUE(Wrapped1->isResolved());<br>
> + EXPECT_FALSE(Wrapped1->isDistinct());<br>
> +<br>
> + // !{!{!{}}}<br>
> + Metadata *Wrapped2Ops[] = {Wrapped1};<br>
> + MDNode *Wrapped2 = MDNode::get(Context, Wrapped2Ops);<br>
> + ASSERT_EQ(Wrapped1, Wrapped2->getOperand(0));<br>
> + ASSERT_TRUE(Wrapped2->isResolved());<br>
> + EXPECT_FALSE(Wrapped2->isDistinct());<br>
> +<br>
> + // !{!{!{}}} => !{!{}}<br>
> + Wrapped2->replaceOperandWith(0, Empty);<br>
> + ASSERT_EQ(Empty, Wrapped2->getOperand(0));<br>
> + EXPECT_TRUE(Wrapped2->isDistinct());<br>
> + EXPECT_FALSE(Wrapped1->isDistinct());<br>
> +}<br>
> +<br>
> typedef MetadataTest MetadataAsValueTest;<br>
><br>
> TEST_F(MetadataAsValueTest, MDNode) {<br>
><br>
><br>
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</div></div></blockquote></div><br></div></div>