[PATCH] compile time improvement for MachineSink

[Aditya Kumar]

REPOSITORY
  rL LLVM

================
Comment at: lib/CodeGen/MachineSink.cpp:175
@@ -173,1 +174,3 @@
+  // since it's possible that they are no longer correct.
+  RegsToClearKillFlags.set(SrcReg);
 
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In line: 154, we check that SrcReg has only one non-debug-use. So I'm wondering why we need to clear kill flags in the entire function when there will be only one use of SrcReg i.e., in MI which is erased anyway.

================
Comment at: lib/CodeGen/MachineSink.cpp:769
@@ -756,6 +768,3 @@
 
-  // Conservatively, clear any kill flags, since it's possible that they are no
-  // longer correct.
-  // Note that we have to clear the kill flags for any register this instruction
-  // uses as we may sink over another instruction which currently kills the
-  // used registers.
+  // Conservatively, record regsters to clear any kill flags later,
+  // since it's possible that they are no longer correct.
----------------
Typo: `registers'

http://reviews.llvm.org/D9719

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