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[Speculation] NFC: more header comments

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explaining how it differs from SpeculativeExecuteBB in SimplifyCFG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237724 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jingyue Wu
2015-05-19 20:52:45 +00:00
parent 65266361a1
commit 31d2ee7360
1 changed files with 9 additions and 0 deletions
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9
lib/Transforms/Scalar/SpeculativeExecution.cpp
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@@ -41,6 +41,15 @@
// Later passes sink back much of the speculated code that did not enable // Later passes sink back much of the speculated code that did not enable
// further optimization. // further optimization.
// //
// This pass is more aggressive than the function SpeculativeyExecuteBB in
// SimplifyCFG. SimplifyCFG will not speculate if no selects are introduced and
// it will speculate at most one instruction. It also will not speculate if
// there is a value defined in the if-block that is only used in the then-block.
// These restrictions make sense since the speculation in SimplifyCFG seems
// aimed at introducing cheap selects, while this pass is intended to do more
// aggressive speculation while counting on later passes to either capitalize on
// that or clean it up.
//
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallSet.h"