[PATCH] Add a speculative execution pass

[Mark Heffernan]

================
Comment at: lib/Transforms/Scalar/SpeculativeExecution.cpp:64
@@ +63,3 @@
+             "the number of instructions that cannot be speculatively executed "
+             "do not exceed this limit."));
+
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The double negative at the end of this description confused me as written.  Maybe:  "Speculative execution is not be applied to basic blocks where the number of ... exceeds this limit."

Could change the other option description to match.

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Comment at: lib/Transforms/Scalar/SpeculativeExecution.cpp:146
@@ +145,3 @@
+        return 1;
+      return 2; // Changed by Jingyue.
+
----------------
Stale comment?

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Comment at: lib/Transforms/Scalar/SpeculativeExecution.cpp:159
@@ +158,3 @@
+    case Instruction::ZExt:
+    case Instruction::SExt:
+      return 1; // These are all cheap.
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Instruction::And?  Can you use TTI instruction costs here?

http://reviews.llvm.org/D9360

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