[llvm-commits] [llvm] r111913 - /llvm/trunk/lib/AsmParser/LLParser.h
Dan Gohman
gohman at apple.com
Tue Aug 24 07:31:06 PDT 2010
Author: djg
Date: Tue Aug 24 09:31:06 2010
New Revision: 111913
URL: http://llvm.org/viewvc/llvm-project?rev=111913&view=rev
Log:
Add a comment explaining why this code is more complex than it
initially seems it should require.
Modified:
llvm/trunk/lib/AsmParser/LLParser.h
Modified: llvm/trunk/lib/AsmParser/LLParser.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLParser.h?rev=111913&r1=111912&r2=111913&view=diff
==============================================================================
--- llvm/trunk/lib/AsmParser/LLParser.h (original)
+++ llvm/trunk/lib/AsmParser/LLParser.h Tue Aug 24 09:31:06 2010
@@ -80,6 +80,14 @@
// Instruction metadata resolution. Each instruction can have a list of
// MDRef info associated with them.
+ //
+ // The simpler approach of just creating temporary MDNodes and then calling
+ // RAUW on them when the definition is processed doesn't work because some
+ // instruction metadata kinds, such as dbg, get stored in the IR in an
+ // "optimized" format which doesn't participate in the normal value use
+ // lists. This means that RAUW doesn't work, even on temporary MDNodes
+ // which otherwise support RAUW. Instead, we defer resolving MDNode
+ // references until the definitions have been processed.
struct MDRef {
SMLoc Loc;
unsigned MDKind, MDSlot;
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