diff options
Diffstat (limited to 'llvm/lib/Transforms/Scalar/JumpThreading.cpp')
-rw-r--r-- | llvm/lib/Transforms/Scalar/JumpThreading.cpp | 26 |
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 |