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| author | Manman Ren <manman.ren@gmail.com> | 2014-03-26 22:14:09 +0000 |
|---|---|---|
| committer | Manman Ren <manman.ren@gmail.com> | 2014-03-26 22:14:09 +0000 |
| commit | 3d7d0bc71a858bdd251a84f7a58a379894afe118 (patch) | |
| tree | a44b079b2c0dc89dbd5a8a26447cd245248247df /lib/CodeGen/RegAllocGreedy.cpp | |
| parent | 2a6873fdf3fa413cd7ef09b368fab64aa936d027 (diff) | |
| download | llvm-3d7d0bc71a858bdd251a84f7a58a379894afe118.tar.gz llvm-3d7d0bc71a858bdd251a84f7a58a379894afe118.tar.bz2 llvm-3d7d0bc71a858bdd251a84f7a58a379894afe118.tar.xz | |
Add comments. Addressing review comments from Evan on r204690.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204864 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/RegAllocGreedy.cpp')
| -rw-r--r-- | lib/CodeGen/RegAllocGreedy.cpp | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp index 3a4ad620d0..a4f6b682a2 100644 --- a/lib/CodeGen/RegAllocGreedy.cpp +++ b/lib/CodeGen/RegAllocGreedy.cpp @@ -2122,6 +2122,11 @@ unsigned RAGreedy::selectOrSplitImpl(LiveInterval &VirtReg, CSRFirstUse = true; BlockFrequency CSRCost(CSRFirstTimeCost); + // Using a CSR for the first time has a cost because it causes push|pop + // to be added to prologue|epilogue. Splitting a cold section of the live + // range can have lower cost than using the CSR for the first time; + // Spilling a live range in the cold path can have lower cost than using + // the CSR for the first time. if (getStage(VirtReg) == RS_Spill && CSRFirstUse && NewVRegs.empty() && CSRFirstTimeCost > 0 && VirtReg.isSpillable()) { // We choose spill over using the CSR for the first time if the spill cost |