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-rw-r--r--llvm/lib/Transforms/Scalar/JumpThreading.cpp26
1 files changed, 16 insertions, 10 deletions
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 5c16b2c5de0..087ce8ac50d 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -286,6 +286,21 @@ static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB,
// FIXME: THREADING will delete values that are just used to compute the
// branch, so they shouldn't count against the duplication cost.
+ unsigned Bonus = 0;
+ const TerminatorInst *BBTerm = BB->getTerminator();
+ // Threading through a switch statement is particularly profitable. If this
+ // block ends in a switch, decrease its cost to make it more likely to happen.
+ if (isa<SwitchInst>(BBTerm))
+ Bonus = 6;
+
+ // The same holds for indirect branches, but slightly more so.
+ if (isa<IndirectBrInst>(BBTerm))
+ Bonus = 8;
+
+ // Bump the threshold up so the early exit from the loop doesn't skip the
+ // terminator-based Size adjustment at the end.
+ Threshold += Bonus;
+
// Sum up the cost of each instruction until we get to the terminator. Don't
// include the terminator because the copy won't include it.
unsigned Size = 0;
@@ -326,16 +341,7 @@ static unsigned getJumpThreadDuplicationCost(const BasicBlock *BB,
}
}
- // Threading through a switch statement is particularly profitable. If this
- // block ends in a switch, decrease its cost to make it more likely to happen.
- if (isa<SwitchInst>(I))
- Size = Size > 6 ? Size-6 : 0;
-
- // The same holds for indirect branches, but slightly more so.
- if (isa<IndirectBrInst>(I))
- Size = Size > 8 ? Size-8 : 0;
-
- return Size;
+ return Size > Bonus ? Size - Bonus : 0;
}
/// FindLoopHeaders - We do not want jump threading to turn proper loop
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