[PATCH] [TargetInstrInfo] Add new hook: AnalyzeBranchPredicate.

[Andrew Trick]

Looks good but I have one comment inline...


================
Comment at: lib/Target/X86/X86InstrInfo.cpp:3640-3641
@@ +3639,4 @@
+  MBP.ConditionDef = &*DefFlagsI;
+  MBP.SingleUseCondition = CondBranches.size() == 1 &&
+                           CondBranches[0]->killsRegister(X86::EFLAGS, TRI);
+
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This looks strange to me. Do you really need to prove that the ConditionDef only has a single use? If so, I think you should:

- check that EFLAGS is not live into any successors

- Walk backward from the branch looking for a Def of EFLAGS before any other use of EFLAGS.

You may have EFLAGS readers other than conditional branches.
killsRegister is a crutch that should be avoided whenever possible. It might not be accurate.

http://reviews.llvm.org/D10200

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