[PATCH] D71375: [X86] Remove EFLAGS from live-in lists of successor MBBs in X86FlagsCopyLowering

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/lib/Target/X86/X86FlagsCopyLowering.cpp:523
 
+      // After this, EFLAGS will be recreated before each use.
+      if (&UseMBB != &MBB)
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I don't think we can do this here. Later we check for successor blocks with livein eflags and I believe we expect to be able to get back to the original MBB that started the worklist as second time if there is a loop. We don't put the initial block into the visited set until its queued as a successor. But we need the eflags livein in order to queue it.


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Comment at: llvm/lib/Target/X86/X86FlagsCopyLowering.cpp:532
       // when the block is the same block as the copy is from, we will visit it
       // twice. The first time we start from the copy and go to the end. The
       // second time we start from the beginning and go to the copy. This lets
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Here the comments talk about visiting the block twice.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71375/new/

https://reviews.llvm.org/D71375